Effect of chemical and mechanical weed control on cassava yield, soil quality and erosion under cassava cropping system

NASA Astrophysics Data System (ADS)

Islami, Titiek; Wisnubroto, Erwin; Utomo, Wani

2016-04-01

Three years field experiments were conducted to study the effect of chemical and mechanical weed control on soil quality and erosion under cassava cropping system. The experiment were conducted at University Brawijaya field experimental station, Jatikerto, Malang, Indonesia. The experiments were carried out from 2011 - 2014. The treatments consist of three cropping system (cassava mono culture; cassava + maize intercropping and cassava + peanut intercropping), and two weed control method (chemical and mechanical methods). The experimental result showed that the yield of cassava first year and second year did not influenced by weed control method and cropping system. However, the third year yield of cassava was influence by weed control method and cropping system. The cassava yield planted in cassava + maize intercropping system with chemical weed control methods was only 24 t/ha, which lower compared to other treatments, even with that of the same cropping system used mechanical weed control. The highest cassava yield in third year was obtained by cassava + peanuts cropping system with mechanical weed control method. After three years experiment, the soil of cassava monoculture system with chemical weed control method possessed the lowest soil organic matter, and soil aggregate stability. During three years of cropping soil erosion in chemical weed control method, especially on cassava monoculture, was higher compared to mechanical weed control method. The soil loss from chemical control method were 40 t/ha, 44 t/ha and 54 t/ha for the first, second and third year crop. The soil loss from mechanical weed control method for the same years was: 36 t/ha, 36 t/ha and 38 t/ha. Key words: herbicide, intercropping, soil organic matter, aggregate stability.

Weed interference with peppermint (Mentha x piperita L.) and spearmint (Mentha spicata L.) crops under different herbicide treatments: effects on biomass and essential oil yield.

PubMed

Karkanis, Anestis; Lykas, Christos; Liava, Vasiliki; Bezou, Anna; Petropoulos, Spyridon; Tsiropoulos, Nikolaos

2018-01-01

'Minor crops' such as spearmint and peppermint are high added value crops, despite the fact that their production area is comparably small worldwide. The main limiting factor in mint commercial cultivation is weed competition. Thus, field experiments were carried out to evaluate the effects of weed interference on growth, biomass and essential oil yield in peppermint and spearmint under different herbicide treatments. The application of pendimethalin and oxyfluorfen provided better control of annual weeds resulting in higher crop yield. Additionally, when treated with herbicides both crops were more competitive against annual weeds in the second year than in the first year. All pre-emergence herbicides increased biomass yield, since pendimethalin, linuron and oxyfluorfen reduced the density of annual weeds by 71-92%, 63-74% and 86-95%, respectively. Weed interference and herbicide application had no effect on essential oil content; however, a relatively strong impact on essential oil production per cultivated area unit was observed, mainly due to the adverse effect of weed interference on plant growth. Considering that pendimethalin and oxyfluorfen were effective against annual weeds in both spearmint and peppermint crops, these herbicides should be included in integrated weed management systems for better weed management in mint crops. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Weed control and cover crop management affect mycorrhizal colonization of grapevine roots and arbuscular mycorrhizal fungal spore populations in a California vineyard.

PubMed

Baumgartner, Kendra; Smith, Richard F; Bettiga, Larry

2005-03-01

Arbuscular mycorrhizal (AM) fungi naturally colonize grapevines in California vineyards. Weed control and cover cropping may affect AM fungi directly, through destruction of extraradical hyphae by soil disruption, or indirectly, through effects on populations of mycorrhizal weeds and cover crops. We examined the effects of weed control (cultivation, post-emergence herbicides, pre-emergence herbicides) and cover crops (Secale cereale cv. Merced rye, x Triticosecale cv.Trios 102) on AM fungi in a Central Coast vineyard. Seasonal changes in grapevine mycorrhizal colonization differed among weed control treatments, but did not correspond with seasonal changes in total weed frequency. Differences in grapevine colonization among weed control treatments may be due to differences in mycorrhizal status and/or AM fungal species composition among dominant weed species. Cover crops had no effect on grapevine mycorrhizal colonization, despite higher spring spore populations in cover cropped middles compared to bare middles. Cover crops were mycorrhizal and shared four AM fungal species (Glomus aggregatum, G. etunicatum, G. mosseae, G. scintillans) in common with grapevines. Lack of contact between grapevine roots and cover crop roots may have prevented grapevines from accessing higher spore populations in the middles.

Weed Diversity Affects Soybean and Maize Yield in a Long Term Experiment in Michigan, USA.

PubMed

Ferrero, Rosana; Lima, Mauricio; Davis, Adam S; Gonzalez-Andujar, Jose L

2017-01-01

Managing production environments in ways that promote weed community diversity may enhance both crop production and the development of a more sustainable agriculture. This study analyzed data of productivity of maize (corn) and soybean in plots in the Main Cropping System Experiment (MCSE) at the W. K. Kellogg Biological Station Long-Term Ecological Research (KBS-LTER) in Michigan, USA, from 1996 to 2011. We used models derived from population ecology to explore how weed diversity, temperature, and precipitation interact with crop yields. Using three types of models that considered internal and external (climate and weeds) factors, with additive or non-linear variants, we found that changes in weed diversity were associated with changes in rates of crop yield increase over time for both maize and soybeans. The intrinsic capacity for soybean yield increase in response to the environment was greater under more diverse weed communities. Soybean production risks were greatest in the least weed diverse systems, in which each weed species lost was associated with progressively greater crop yield losses. Managing for weed community diversity, while suppressing dominant, highly competitive weeds, may be a helpful strategy for supporting long term increases in soybean productivity. In maize, there was a negative and non-additive response of yields to the interaction between weed diversity and minimum air temperatures. When cold temperatures constrained potential maize productivity through limited resources, negative interactions with weed diversity became more pronounced. We suggest that: (1) maize was less competitive in cold years allowing higher weed diversity and the dominance of some weed species; or (2) that cold years resulted in increased weed richness and prevalence of competitive weeds, thus reducing crop yields. Therefore, we propose to control dominant weed species especially in the years of low yield and extreme minimum temperatures to improve maize yields. Results of our study indicate that through the proactive management of weed diversity, it may be possible to promote both high productivity of crops and environmental sustainability.

Weed Diversity Affects Soybean and Maize Yield in a Long Term Experiment in Michigan, USA

PubMed Central

Ferrero, Rosana; Lima, Mauricio; Davis, Adam S.; Gonzalez-Andujar, Jose L.

2017-01-01

Managing production environments in ways that promote weed community diversity may enhance both crop production and the development of a more sustainable agriculture. This study analyzed data of productivity of maize (corn) and soybean in plots in the Main Cropping System Experiment (MCSE) at the W. K. Kellogg Biological Station Long-Term Ecological Research (KBS-LTER) in Michigan, USA, from 1996 to 2011. We used models derived from population ecology to explore how weed diversity, temperature, and precipitation interact with crop yields. Using three types of models that considered internal and external (climate and weeds) factors, with additive or non-linear variants, we found that changes in weed diversity were associated with changes in rates of crop yield increase over time for both maize and soybeans. The intrinsic capacity for soybean yield increase in response to the environment was greater under more diverse weed communities. Soybean production risks were greatest in the least weed diverse systems, in which each weed species lost was associated with progressively greater crop yield losses. Managing for weed community diversity, while suppressing dominant, highly competitive weeds, may be a helpful strategy for supporting long term increases in soybean productivity. In maize, there was a negative and non-additive response of yields to the interaction between weed diversity and minimum air temperatures. When cold temperatures constrained potential maize productivity through limited resources, negative interactions with weed diversity became more pronounced. We suggest that: (1) maize was less competitive in cold years allowing higher weed diversity and the dominance of some weed species; or (2) that cold years resulted in increased weed richness and prevalence of competitive weeds, thus reducing crop yields. Therefore, we propose to control dominant weed species especially in the years of low yield and extreme minimum temperatures to improve maize yields. Results of our study indicate that through the proactive management of weed diversity, it may be possible to promote both high productivity of crops and environmental sustainability. PMID:28286509

Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production

PubMed Central

Odhiambo, Judith A.; Norton, Urszula; Ashilenje, Dennis; Omondi, Emmanuel C.; Norton, Jay B.

2015-01-01

Weed competition is a significant problem in maize (Zea mays, L.) production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L.) during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT), no-till (NT) and conventional (CT) applied to three cropping systems: continuous maize/bean intercropping (TYPICAL), maize/bean intercropping with relayed mucuna after bean harvest (RELAY) and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP). Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha-1 in MT and $149.60 ha-1 in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations. PMID:26237404

Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production.

PubMed

Odhiambo, Judith A; Norton, Urszula; Ashilenje, Dennis; Omondi, Emmanuel C; Norton, Jay B

2015-01-01

Weed competition is a significant problem in maize (Zea mays, L.) production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L.) during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT), no-till (NT) and conventional (CT) applied to three cropping systems: continuous maize/bean intercropping (TYPICAL), maize/bean intercropping with relayed mucuna after bean harvest (RELAY) and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP). Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha(-1) in MT and $149.60 ha(-1) in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations.

Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds?

PubMed Central

Veiga, Rita S. L.; Jansa, Jan; Frossard, Emmanuel; van der Heijden, Marcel G. A.

2011-01-01

Background Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions. Methodology/Principal Findings First, under controlled glasshouse conditions, we screened growth responses of nine weed species and three crops to a widespread AMF, Glomus intraradices. None of the weeds screened showed a significant positive mycorrhizal growth response and four weed species were significantly reduced by the AMF (growth responses between −22 and −35%). In a subsequent experiment, we selected three of the negatively responding weed species – Echinochloa crus-galli, Setaria viridis and Solanum nigrum – and analyzed their responses to a combination of three AMF (Glomus intraradices, Glomus mosseae and Glomus claroideum). Finally, we tested whether the presence of a crop (maize) enhanced the suppressive effect of AMF on weeds. We found that the growth of the three selected weed species was also reduced by a combination of AMF and that the presence of maize amplified the negative effect of AMF on the growth of E. crus-galli. Conclusions/Significance Our results show that AMF can negatively influence the growth of some weed species indicating that AMF have the potential to act as determinants of weed community structure. Furthermore, mycorrhizal weed growth reductions can be amplified in the presence of a crop. Previous studies have shown that AMF provide a number of beneficial ecosystem services. Taken together with our current results, the maintenance and promotion of AMF activity may thereby contribute to sustainable management of agroecosystems. However, in order to further the practical and ecological relevance of our findings, additional experiments should be performed under field conditions. PMID:22164216

Meteorological and management factors influencing weed abundance during 18 years of organic crop rotations

USDA-ARS?s Scientific Manuscript database

Organic crop production is often limited by the inability to control weeds. An 18-year dataset of weed cover in organic crop rotations at the long-term Farming Systems Project at Beltsville, Maryland, provided the opportunity to identify meteorological and management factors influencing weed abundan...

Weed Identification and Control in Vegetable Crops.

ERIC Educational Resources Information Center

Ferretti, Peter A., Comp.

This agriculture extension service publication from Pennsylvania State University examines weed control and identification in vegetable crops. Contents include: (1) Types of weeds; (2) Reducing losses caused by weeds, general control methods and home garden weed control; (3) How herbicides are used; (4) Specific weeds in vegetable plantings; and…

Integrated pest management and weed management in the United States and Canada.

PubMed

Owen, Micheal D K; Beckie, Hugh J; Leeson, Julia Y; Norsworthy, Jason K; Steckel, Larry E

2015-03-01

There is interest in more diverse weed management tactics because of evolved herbicide resistance in important weeds in many US and Canadian crop systems. While herbicide resistance in weeds is not new, the issue has become critical because of the adoption of simple, convenient and inexpensive crop systems based on genetically engineered glyphosate-tolerant crop cultivars. Importantly, genetic engineering has not been a factor in rice and wheat, two globally important food crops. There are many tactics that help to mitigate herbicide resistance in weeds and should be widely adopted. Evolved herbicide resistance in key weeds has influenced a limited number of growers to include a more diverse suite of tactics to supplement existing herbicidal tactics. Most growers still emphasize herbicides, often to the exclusion of alternative tactics. Application of integrated pest management for weeds is better characterized as integrated weed management, and more typically integrated herbicide management. However, adoption of diverse weed management tactics is limited. Modifying herbicide use will not solve herbicide resistance in weeds, and the relief provided by different herbicide use practices is generally short-lived at best. More diversity of tactics for weed management must be incorporated in crop systems. © 2014 Society of Chemical Industry.

Integrated weed management systems with herbicide-tolerant crops in the European Union: lessons learnt from home and abroad.

PubMed

Lamichhane, Jay Ram; Devos, Yann; Beckie, Hugh J; Owen, Micheal D K; Tillie, Pascal; Messéan, Antoine; Kudsk, Per

2017-06-01

Conventionally bred (CHT) and genetically modified herbicide-tolerant (GMHT) crops have changed weed management practices and made an important contribution to the global production of some commodity crops. However, a concern is that farm management practices associated with the cultivation of herbicide-tolerant (HT) crops further deplete farmland biodiversity and accelerate the evolution of herbicide-resistant (HR) weeds. Diversification in crop systems and weed management practices can enhance farmland biodiversity, and reduce the risk of weeds evolving herbicide resistance. Therefore, HT crops are most effective and sustainable as a component of an integrated weed management (IWM) system. IWM advocates the use of multiple effective strategies or tactics to manage weed populations in a manner that is economically and environmentally sound. In practice, however, the potential benefits of IWM with HT crops are seldom realized because a wide range of technical and socio-economic factors hamper the transition to IWM. Here, we discuss the major factors that limit the integration of HT crops and their associated farm management practices in IWM systems. Based on the experience gained in countries where CHT or GMHT crops are widely grown and the increased familiarity with their management, we propose five actions to facilitate the integration of HT crops in IWM systems within the European Union.

Potential synergistic effects of cereal rye biomass and soybean planting density on weed suppression

USDA-ARS?s Scientific Manuscript database

Increasing crop density is a cultural weed management practice that can complement the use of cover crops for weed suppression. In this research, we created a range of cover crop biomass and soybean densities in order to assess their weed suppressive ability alone and in combination. The experiment ...

Weed Growth Stage Estimator Using Deep Convolutional Neural Networks.

PubMed

Teimouri, Nima; Dyrmann, Mads; Nielsen, Per Rydahl; Mathiassen, Solvejg Kopp; Somerville, Gayle J; Jørgensen, Rasmus Nyholm

2018-05-16

This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across variable environmental conditions with regards to soil types, resolution and light settings. Then, 9649 of these images were used for training the computer, which automatically divided the weeds into nine growth classes. The performance of this proposed convolutional neural network approach was evaluated on a further set of 2516 images, which also varied in term of crop, soil type, image resolution and light conditions. The overall performance of this approach achieved a maximum accuracy of 78% for identifying Polygonum spp. and a minimum accuracy of 46% for blackgrass. In addition, it achieved an average 70% accuracy rate in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species.

Opportunities and challenges for harvest weed seed control in global cropping systems.

PubMed

Walsh, Michael J; Broster, John C; Schwartz-Lazaro, Lauren M; Norsworthy, Jason K; Davis, Adam S; Tidemann, Breanne D; Beckie, Hugh J; Lyon, Drew J; Soni, Neeta; Neve, Paul; Bagavathiannan, Muthukumar V

2017-11-28

The opportunity to target weed seeds during grain harvest was established many decades ago following the introduction of mechanical harvesting and the recognition of high weed-seed retention levels at crop maturity; however, this opportunity remained largely neglected until more recently. The introduction and adoption of harvest weed seed control (HWSC) systems in Australia has been in response to widespread occurrence of herbicide-resistant weed populations. With diminishing herbicide resources and the need to maintain highly productive reduced tillage and stubble-retention practices, growers began to develop systems that targeted weed seeds during crop harvest. Research and development efforts over the past two decades have established the efficacy of HWSC systems in Australian cropping systems, where widespread adoption is now occurring. With similarly dramatic herbicide resistance issues now present across many of the world's cropping regions, it is timely for HWSC systems to be considered for inclusion in weed-management programs in these areas. This review describes HWSC systems and establishing the potential for this approach to weed control in several cropping regions. As observed in Australia, the inclusion of HWSC systems can reduce weed populations substantially reducing the potential for weed adaptation and resistance evolution. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Benchmark study on glyphosate-resistant cropping systems in the United States. Part 4: Weed management practices and effects on weed populations and soil seedbanks.

PubMed

Wilson, Robert G; Young, Bryan G; Matthews, Joseph L; Weller, Stephen C; Johnson, William G; Jordan, David L; Owen, Micheal D K; Dixon, Philip M; Shaw, David R

2011-07-01

Weed management in glyphosate-resistant (GR) maize, cotton and soybean in the United States relies almost exclusively on glyphosate, which raises criticism for facilitating shifts in weed populations. In 2006, the benchmark study, a field-scale investigation, was initiated in three different GR cropping systems to characterize academic recommendations for weed management and to determine the level to which these recommendations would reduce weed population shifts. A majority of growers used glyphosate as the only herbicide for weed management, as opposed to 98% of the academic recommendations implementing at least two herbicide active ingredients and modes of action. The additional herbicides were applied with glyphosate and as soil residual treatments. The greater herbicide diversity with academic recommendations reduced weed population densities before and after post-emergence herbicide applications in 2006 and 2007, particularly in continuous GR crops. Diversifying herbicides reduces weed population densities and lowers the risk of weed population shifts and the associated potential for the evolution of glyphosate-resistant weeds in continuous GR crops. Altered weed management practices (e.g. herbicides or tillage) enabled by rotating crops, whether GR or non-GR, improves weed management and thus minimizes the effectiveness of only using chemical tactics to mitigate weed population shifts. Copyright © 2011 Society of Chemical Industry.

Hyperspectral imaging for differentiating glyphosate-resistant and glyphosate-susceptible Italian Ryegrass

USDA-ARS?s Scientific Manuscript database

Glyphosate is widely used in row crop weed control programs of glyphosate-resistant (GR) crops. With the accumulation of glyphosate use, several weeds have evolved resistance to glyphosate. In order to control GR weeds for profitable crop production, it is critical to first identify them in crop fie...

Reducing Freshwater Toxicity while Maintaining Weed Control, Profits, And Productivity: Effects of Increased Crop Rotation Diversity and Reduced Herbicide Usage.

PubMed

Hunt, Natalie D; Hill, Jason D; Liebman, Matt

2017-02-07

Increasing crop rotation diversity while reducing herbicide applications may maintain effective weed control while reducing freshwater toxicity. To test this hypothesis, we applied the model USEtox 2.0 to data from a long-term Iowa field experiment that included three crop rotation systems: a 2-year corn-soybean sequence, a 3-year corn-soybean-oat/red clover sequence, and 4-year corn-soybean-oat/alfalfa-alfalfa sequence. Corn and soybean in each rotation were managed with conventional or low-herbicide regimes. Oat, red clover, and alfalfa were not treated with herbicides. Data from 2008-2015 showed that use of the low-herbicide regime reduced freshwater toxicity loads by 81-96%, and that use of the more diverse rotations reduced toxicity and system dependence on herbicides by 25-51%. Mean weed biomass in corn and soybean was <25 kg ha -1 in all rotation × herbicide combinations except the low-herbicide 3-year rotation, which contained ∼110 kg ha -1 of weed biomass. Corn and soybean yields and net returns were as high or higher for the 3- and 4-year rotations managed with the low-herbicide regime as for the conventional-herbicide 2-year rotation. These results indicate that certain forms of cropping system diversification and alternative weed management strategies can maintain yield, profit, and weed suppression while delivering enhanced environmental performance.

Weed presence altered biotic stress and light signaling in maize even when weeds were removed early in the critical weed-free period

USDA-ARS?s Scientific Manuscript database

Weeds reduce crop yield even when there is no competition for resources. A phenomena known as the critical weed-free period (CWFP), which occurs early in the crop’s life cycle, is the essential interval when weed presence can reduce crop growth and yield. Even when weeds are removed after the CWFP, ...

Management of herbicide resistance in wheat cropping systems: learning from the Australian experience.

PubMed

Walsh, Michael J; Powles, Stephen B

2014-09-01

Herbicide resistance continues to escalate in weed populations infesting global wheat (Triticum aestivum L.) crops, threatening grain production and thereby food supply. Conservation wheat production systems are reliant on the use of efficient herbicides providing low-cost, selective weed control in intensive cropping systems. The resistance-driven loss of herbicide resources combined with limited potential for new herbicide molecules means greater emphasis must be placed on preserving existing herbicides. For more than two decades, since the initial recognition of the dramatic consequences of herbicide resistance, the challenge of introducing additional weed control strategies into herbicide-based weed management programmes has been formidable. Throughout this period, herbicide resistance has expanded unabated across the world's wheat production regions. However, in Australia, where herbicide resources have become desperately depleted, the adoption of harvest weed seed control is evidence, at last, of a successful approach to sustainable weed management in wheat production systems. Growers routinely including strategies to target weed seeds during crop harvest, as part of herbicide-based weed management programmes, are now realising significant weed control and crop production benefits. When combined with an attitude of zero weed tolerance, there is evidence of a sustainable weed control future for wheat production systems. The hard-learned lessons of Australian growers can now be viewed by global wheat producers as an example of how to stop the continual loss of herbicide resources in productive cropping systems. © 2013 Society of Chemical Industry.

The benefits of herbicide-resistant crops.

PubMed

Green, Jerry M

2012-10-01

Since 1996, genetically modified herbicide-resistant crops, primarily glyphosate-resistant soybean, corn, cotton and canola, have helped to revolutionize weed management and have become an important tool in crop production practices. Glyphosate-resistant crops have enabled the implementation of weed management practices that have improved yield and profitability while better protecting the environment. Growers have recognized their benefits and have made glyphosate-resistant crops the most rapidly adopted technology in the history of agriculture. Weed management systems with glyphosate-resistant crops have often relied on glyphosate alone, have been easy to use and have been effective, economical and more environmentally friendly than the systems they have replaced. Glyphosate has worked extremely well in controlling weeds in glyphosate-resistant crops for more than a decade, but some key weeds have evolved resistance, and using glyphosate alone has proved unsustainable. Now, growers need to renew their weed management practices and use glyphosate with other cultural, mechanical and herbicide options in integrated systems. New multiple-herbicide-resistant crops with resistance to glyphosate and other herbicides will expand the utility of existing herbicide technologies and will be an important component of future weed management systems that help to sustain the current benefits of high-efficiency and high-production agriculture. Copyright © 2012 Society of Chemical Industry.

Genetically Modified Herbicide-Tolerant Crops, Weeds, and Herbicides: Overview and Impact.

PubMed

Bonny, Sylvie

2016-01-01

Genetically modified (GM) crops have been and continue to be a subject of controversy despite their rapid adoption by farmers where approved. For the last two decades, an important matter of debate has been their impact on pesticide use, particularly for herbicide-tolerant (HT) crops. Some claim that these crops bring about a decrease in herbicide use, while others claim the opposite. In fact, since 1996, most cultivated GMOs have been GMHT crops, which involve the use of an associated herbicide, generally glyphosate. In their very first years of adoption, HT crops often led to some decrease in herbicide use. However, the repetition of glyphosate-tolerant crops and of glyphosate only applications in the same fields without sufficient alternation and herbicide diversity has contributed to the appearance of glyphosate-resistant weeds. These weeds have resulted in a rise in the use of glyphosate and other herbicides. This article explores this situation and the impacts of herbicide-resistant weeds, using an interdisciplinary approach and drawing on recent data. The paper analyzes the spread of GMHT crops worldwide and their consequences on herbicide use in the USA in particular. It then addresses the global development of glyphosate-resistant weeds and their impact, particularly focusing on the USA. Finally, the last section explores how industry, farmers, and weed scientists are coping with the spread of resistant weeds. The concluding comments deal more widely with trends in GM crops.

Genetically Modified Herbicide-Tolerant Crops, Weeds, and Herbicides: Overview and Impact

NASA Astrophysics Data System (ADS)

Bonny, Sylvie

2016-01-01

Genetically modified (GM) crops have been and continue to be a subject of controversy despite their rapid adoption by farmers where approved. For the last two decades, an important matter of debate has been their impact on pesticide use, particularly for herbicide-tolerant (HT) crops. Some claim that these crops bring about a decrease in herbicide use, while others claim the opposite. In fact, since 1996, most cultivated GMOs have been GMHT crops, which involve the use of an associated herbicide, generally glyphosate. In their very first years of adoption, HT crops often led to some decrease in herbicide use. However, the repetition of glyphosate-tolerant crops and of glyphosate only applications in the same fields without sufficient alternation and herbicide diversity has contributed to the appearance of glyphosate-resistant weeds. These weeds have resulted in a rise in the use of glyphosate and other herbicides. This article explores this situation and the impacts of herbicide-resistant weeds, using an interdisciplinary approach and drawing on recent data. The paper analyzes the spread of GMHT crops worldwide and their consequences on herbicide use in the USA in particular. It then addresses the global development of glyphosate-resistant weeds and their impact, particularly focusing on the USA. Finally, the last section explores how industry, farmers, and weed scientists are coping with the spread of resistant weeds. The concluding comments deal more widely with trends in GM crops.

Allelopathic effect of Bromus spp. and Lolium spp. shoot extracts on some crops.

PubMed

Lehoczky, E; Nelima, M Okumu; Szabó, R; Szalai, A; Nagy, P

2011-01-01

Allelopathy is an untapped resource for weed control in crops that could give good possibilities for environmentally sound, integrated crop production. Allelopathy is defined as the direct or indirect harmful or beneficial effects of one plant on another through the production of chemical compounds, called allelochemicals, which escape into the environment. Allelochemicals can be produced by weeds and affect crops, and the reverse is also true. Allelopathic interactions include weed-weed, weed-crop, and crop-crop. Allelopathy offers potential for selective biological weed control for instance weed-suppressing crops and the use of plant residues in cropping systems, allelopathic rotational crops, or companion plants with allelopathic potential. Bromus species occur in many habitats in temperate regions of the world, including America, Eurasia, Australia, and Africa. The genus Lolium is one of the most important forage grasses. The weed species usually grow in the same production zones as wheat and are considered weeds since they parasitize wheat fields. Some of the weed species in these two genus have been reported to have allelopathic effect. One of the methods that has been successful in studying allelopathic activity are bioassays. Laboratory experiments were conducted to determine allelopathic effect of watery shoot extracts of four weed species of the Poaceae family, namely Bromus rigidus, Bromus diandrus, Lolium multiflorum and Lolium temulentum on germination and growth of winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), corn (Zea mays L), perennial ryegrass (Lolium perenne L.), bean (Phaseolus sp.) and sunflower (Helianthus annuus L.) and on each other. The experiment was carried out during the period March 2010 to October 2010. Twenty five seeds were put into one Petri-dish on filter paper, adding 15ml of extract to each in four repeats. The germination took place in a Binder-type thermostat in the dark. The timing of germination was checked in every two days and the rate of growth was estimated after a week, by counting the number of germinated seeds and measuring the length of the radicle and plumule. The measured data was statistically analyzed and the effect of the extracts on germination percentage and seedling length was evaluated.

Meta-analysis of crop and weed growth responses to arbuscular-mycorrhizal fungi

USDA-ARS?s Scientific Manuscript database

Arbuscular mycorrhizal fungi (AMF) have long been regarded as beneficial soil microorganisms, but have been reported to have detrimental effects on several non-mycorrhizal agricultural weed species. If AMF have negative effects on weeds but neutral or positive effects on crops under certain cropping...

An Ultrasonic System for Weed Detection in Cereal Crops

PubMed Central

Andújar, Dionisio; Weis, Martin; Gerhards, Roland

2012-01-01

Site-specific weed management requires sensing of the actual weed infestation levels in agricultural fields to adapt the management accordingly. However, sophisticated sensor systems are not yet in wider practical use, since they are not easily available for the farmers and their handling as well as the management practice requires additional efforts. A new sensor-based weed detection method is presented in this paper and its applicability to cereal crops is evaluated. An ultrasonic distance sensor for the determination of plant heights was used for weed detection. It was hypothesised that the weed infested zones have a higher amount of biomass than non-infested areas and that this can be determined by plant height measurements. Ultrasonic distance measurements were taken in a winter wheat field infested by grass weeds and broad-leaved weeds. A total of 80 and 40 circular-shaped samples of different weed densities and compositions were assessed at two different dates. The sensor was pointed directly to the ground for height determination. In the following, weeds were counted and then removed from the sample locations. Grass weeds and broad-leaved weeds were separately removed. Differences between weed infested and weed-free measurements were determined. Dry-matter of weeds and crop was assessed and evaluated together with the sensor measurements. RGB images were taken prior and after weed removal to determine the coverage percentages of weeds and crop per sampling point. Image processing steps included EGI (excess green index) computation and thresholding to separate plants and background. The relationship between ultrasonic readings and the corresponding coverage of the crop and weeds were assessed using multiple regression analysis. Results revealed a height difference between infested and non-infested sample locations. Density and biomass of weeds present in the sample influenced the ultrasonic readings. The possibilities of weed group discrimination were assessed by discriminant analysis. The ultrasonic readings permitted the separation between weed infested zones and non-infested areas with up to 92.8% of success. This system will potentially reduce the cost of weed detection and offers an opportunity to its use in non-selective methods for weed control. PMID:23443401

An ultrasonic system for weed detection in cereal crops.

PubMed

Andújar, Dionisio; Weis, Martin; Gerhards, Roland

2012-12-13

Site-specific weed management requires sensing of the actual weed infestation levels in agricultural fields to adapt the management accordingly. However, sophisticated sensor systems are not yet in wider practical use, since they are not easily available for the farmers and their handling as well as the management practice requires additional efforts. A new sensor-based weed detection method is presented in this paper and its applicability to cereal crops is evaluated. An ultrasonic distance sensor for the determination of plant heights was used for weed detection. It was hypothesised that the weed infested zones have a higher amount of biomass than non-infested areas and that this can be determined by plant height measurements. Ultrasonic distance measurements were taken in a winter wheat field infested by grass weeds and broad-leaved weeds. A total of 80 and 40 circular-shaped samples of different weed densities and compositions were assessed at two different dates. The sensor was pointed directly to the ground for height determination. In the following, weeds were counted and then removed from the sample locations. Grass weeds and broad-leaved weeds were separately removed. Differences between weed infested and weed-free measurements were determined. Dry-matter of weeds and crop was assessed and evaluated together with the sensor measurements. RGB images were taken prior and after weed removal to determine the coverage percentages of weeds and crop per sampling point. Image processing steps included EGI (excess green index) computation and thresholding to separate plants and background. The relationship between ultrasonic readings and the corresponding coverage of the crop and weeds were assessed using multiple regression analysis. Results revealed a height difference between infested and non-infested sample locations. Density and biomass of weeds present in the sample influenced the ultrasonic readings. The possibilities of weed group discrimination were assessed by discriminant analysis. The ultrasonic readings permitted the separation between weed infested zones and non-infested areas with up to 92.8% of success. This system will potentially reduce the cost of weed detection and offers an opportunity to its use in non-selective methods for weed control.

The potential of cover crops for improving soil function

NASA Astrophysics Data System (ADS)

Stoate, Chris; Crotty, Felicity

2017-04-01

Cover crops can be grown over the autumn and winter ensuring green cover throughout the year. They have been described as improving soil structure, reducing soil erosion and potentially even a form of grass weed control. These crops retain nutrients within the plant, potentially making them available for future crops, as well as increasing soil organic matter. Over the last three years, we have investigated how different cover crop regimes affect soil quality. Three separate experiments over each autumn/winter period have investigated how different cover crops affect soil biology, physics and chemistry, with each experiment building on the previous one. There have been significant effects of cover crops on soil structure, as well as significantly lower weed biomass and increased yields in the following crop - in comparison to bare stubble. For example, the effect of drilling the cover crops on soil structure in comparison to a bare stubble control that had not been driven on by machinery was quantified, and over the winter period the soil structure of the cover crop treatments changed, with compaction reduced in the cover crop treatments, whilst the bare stubble control remained unchanged. Weeds were found in significantly lower biomass in the cover crop mixes in comparison to the bare stubble control, and significantly lower weed biomass continued to be found in the following spring oat crop where the cover crops had been, indicating a weed suppressive effect that has a continued legacy in the following crop. The following spring oats have shown similar results in the last two years, with higher yields in the previous cover crop areas compared to the bare stubble controls. Overall, these results are indicating that cover crops have the potential to provide improvements to soil quality, reduce weeds and improve yields. We discuss the economic implications.

Robust crop and weed segmentation under uncontrolled outdoor illumination.

PubMed

Jeon, Hong Y; Tian, Lei F; Zhu, Heping

2011-01-01

An image processing algorithm for detecting individual weeds was developed and evaluated. Weed detection processes included were normalized excessive green conversion, statistical threshold value estimation, adaptive image segmentation, median filter, morphological feature calculation and Artificial Neural Network (ANN). The developed algorithm was validated for its ability to identify and detect weeds and crop plants under uncontrolled outdoor illuminations. A machine vision implementing field robot captured field images under outdoor illuminations and the image processing algorithm automatically processed them without manual adjustment. The errors of the algorithm, when processing 666 field images, ranged from 2.1 to 2.9%. The ANN correctly detected 72.6% of crop plants from the identified plants, and considered the rest as weeds. However, the ANN identification rates for crop plants were improved up to 95.1% by addressing the error sources in the algorithm. The developed weed detection and image processing algorithm provides a novel method to identify plants against soil background under the uncontrolled outdoor illuminations, and to differentiate weeds from crop plants. Thus, the proposed new machine vision and processing algorithm may be useful for outdoor applications including plant specific direct applications (PSDA).

[Dynamics and combined injuries of main pest species in rice cropping zones of Yunnan, Southwest China].

PubMed

Dong, Kun; Dong, Yan; Wang, Hai-Long; Zhang, Li-Min; Zan, Qing-An; Chen, Bin; Li, Zheng-Yue

2014-01-01

A series of rice pest injuries (due to pathogens, insects, and weeds) were surveyed in 286 farmers' fields for major rice varieties of three rice cropping zones of Yunnan Province, Southwest China. The composition and dynamics of main pest species were analyzed, and the trend of rice pest succession in Yunnan was discussed based upon landmark publications. The results showed that the three rice cropping zones had different pest characteristics as regard to main species, dynamics and combined injuries. Sheath rot, bacterial leaf blight, rice stripe, leaf hoppers, armyworms and stem borers were serious in the japonica rice zone. Sheath blight and rice stripe were serious in the japonica-indica interlacing zone. Leaf blast, sheath blight, leaf folders and weeds above rice crop canopy were serious in the indica rice zone. False smut, plant hoppers and weeds below rice crop canopy were ubiquitous and serious in the three kinds of rice cropping zones. Many kinds of weed infestation emerged in the whole rice cropping seasons. Echinochloa crusgalli, Sagittaria pygmaea, Potamogeton distinctus and Spirodela polyrhiza were the main species of weeds in the rice cropping zones of Yunnan. Overall, levels of combined injuries due to pests in the japonica rice zone and the indica rice zone were higher than that in the japonica-indica interlacing zone. In terms of the trend of rice pest succession in Yunnan, injuries due to false smut, sheath blight and plant hoppers seemed to be in a worse tendency in all rice cropping zones of Yunnan, while dominants species of weeds in the paddy fields are shifting from the annual weeds to the perennial malignant weeds.

Perspectives on transgenic, herbicide-resistant crops in the United States almost 20 years after introduction.

PubMed

Duke, Stephen O

2015-05-01

Herbicide-resistant crops have had a profound impact on weed management. Most of the impact has been by glyphosate-resistant maize, cotton, soybean and canola. Significant economic savings, yield increases and more efficacious and simplified weed management have resulted in widespread adoption of the technology. Initially, glyphosate-resistant crops enabled significantly reduced tillage and reduced the environmental impact of weed management. Continuous use of glyphosate with glyphosate-resistant crops over broad areas facilitated the evolution of glyphosate-resistant weeds, which have resulted in increases in the use of tillage and other herbicides with glyphosate, reducing some of the initial environmental benefits of glyphosate-resistant crops. Transgenic crops with resistance to auxinic herbicides, as well as to herbicides that inhibit acetolactate synthase, acetyl-CoA carboxylase and hydroxyphenylpyruvate dioxygenase, stacked with glyphosate and/or glufosinate resistance, will become available in the next few years. These technologies will provide additional weed management options for farmers, but will not have all of the positive effects (reduced cost, simplified weed management, lowered environmental impact and reduced tillage) that glyphosate-resistant crops had initially. In the more distant future, other herbicide-resistant crops (including non-transgenic ones), herbicides with new modes of action and technologies that are currently in their infancy (e.g. bioherbicides, sprayable herbicidal RNAi and/or robotic weeding) may affect the role of transgenic, herbicide-resistant crops in weed management. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Effects of peanut stand uniformity and herbicide regime on weed management and yield

USDA-ARS?s Scientific Manuscript database

Crop stand directly affects ability of any crop to compete with weeds. To capture this form of cultural weed control, final crop stands need to be uniform. Peanut stands are frequently non-uniform, despite the use of precision vacuum planters. Trials were conducted from 2009 through 2011 in Tifto...

Influence of Seeding Ratio, Planting Date, and Termination Date on Rye-Hairy Vetch Cover Crop Mixture Performance under Organic Management

PubMed Central

Lawson, Andrew; Cogger, Craig; Bary, Andy; Fortuna, Ann-Marie

2015-01-01

Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO3 --N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha-1 biomass, whereas mixtures averaged 4.1 Mg ha-1 and hairy vetch 2.3 Mg ha-1. Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha-1 N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO3 --N (0 to 30 cm depth) averaged 62 kg ha-1 for rye, 97 kg ha-1 for the mixtures, and 119 kg ha-1 for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures. PMID:26080008

Influence of Seeding Ratio, Planting Date, and Termination Date on Rye-Hairy Vetch Cover Crop Mixture Performance under Organic Management.

PubMed

Lawson, Andrew; Cogger, Craig; Bary, Andy; Fortuna, Ann-Marie

2015-01-01

Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO3(-)-N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha(-1) biomass, whereas mixtures averaged 4.1 Mg ha(-1) and hairy vetch 2.3 Mg ha(-1). Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha(-1) N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO3(-)-N (0 to 30 cm depth) averaged 62 kg ha(-1) for rye, 97 kg ha(-1) for the mixtures, and 119 kg ha(-1) for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures.

Opportunities and challenges for harvest weed seed control in global cropping systems

USDA-ARS?s Scientific Manuscript database

The introduction of mechanical harvesting and the retention of high proportions of weed seed at crop harvest created the opportunity to target weed seeds many decades ago; however, this approach to weed control has been largely neglected until more recently. The introduction and adoption of harvest ...

Current state of herbicides in herbicide-resistant crops.

PubMed

Green, Jerry M

2014-09-01

Current herbicide and herbicide trait practices are changing in response to the rapid spread of glyphosate-resistant weeds. Growers urgently needed glyphosate when glyphosate-resistant crops became available because weeds were becoming widely resistant to most commonly used selective herbicides, making weed management too complex and time consuming for large farm operations. Glyphosate made weed management easy and efficient by controlling all emerged weeds at a wide range of application timings. However, the intensive use of glyphosate over wide areas and concomitant decline in the use of other herbicides led eventually to the widespread evolution of weeds resistant to glyphosate. Today, weeds that are resistant to glyphosate and other herbicide types are threatening current crop production practices. Unfortunately, all commercial herbicide modes of action are over 20 years old and have resistant weed problems. The severity of the problem has prompted the renewal of efforts to discover new weed management technologies. One technology will be a new generation of crops with resistance to glyphosate, glufosinate and other existing herbicide modes of action. Other technologies will include new chemical, biological, cultural and mechanical methods for weed management. From the onset of commercialization, growers must now preserve the utility of new technologies by integrating their use with other weed management technologies in diverse and sustainable systems. © 2014 Society of Chemical Industry.

Eradication of Major Weeds

ERIC Educational Resources Information Center

Indian Journal of Adult Education, 1975

1975-01-01

Strategies for weed control in cropped and non-cropped areas are presented together with an operational plan for implementing a program for weed control at the national level. The program includes training personnel and community education procedures. (EC)

Broccoli/weed/soil discrimination by optical reflectance using neural networks

NASA Astrophysics Data System (ADS)

Hahn, Federico

1995-04-01

Broccoli is grown extensively in Scotland, and has become one of the main vegetables cropped, due to its high yields and profits. Broccoli, weed and soil samples from 6 different farms were collected and their spectra obtained and analyzed using discriminant analysis. High crop/weed/soil discrimination success rates were encountered in each farm, but the selected wavelengths varied in each farm due to differences in broccoli variety, weed species incidence and soil type. In order to use only three wavelengths, neural networks were introduced and high crop/weed/soil discrimination accuracies for each farm were achieved.

Effects of seeding rate and poultry litter on weed suppression from a rolled cereal rye cover crop

USDA-ARS?s Scientific Manuscript database

Growing enough cover crop biomass to adequately suppress weeds is one of the primary challenges in reduced-tillage systems that rely on mulch-based weed suppression. We investigated two approaches to increasing cereal rye biomass for improved weed suppression: (1) increasing soil fertility and (2) i...

Evaluation of tillage, cover crop, & herbicide effects on weed control, yield and grade in peanut?

USDA-ARS?s Scientific Manuscript database

Peanut production continues to play a large role in agriculture in the Southeastern United States and weed challenges persist. Therefore, it is important to reduce weed competition in peanut to protect yield and grade. With traditional use of herbicides for weed control in peanut and rotational crop...

[Effect of conservation tillage on weeds in a rotation system on the Loess Plateau of eastern Gansu, Northwest China].

PubMed

Zhao, Yu-xin; Lu, Jiao-yun; Yang, Hui-min

2015-04-01

A field study was conducted to investigate the influences of no-tillage, stubble retention and crop type on weed density, species composition and community feature in a rotation system (winter wheat-common vetch-maize) established 12 years ago on the Loess Plateau of eastern Gansu. This study showed that the weed species composition, density and community feature varied with the change of crop phases. No-tillage practice increased the weed density at maize phase, while rotation with common vetch decreased the density in the no-tillage field. Stubble retention reduced the weed density under maize phase and the lowest density was observed in the no-tillage plus stubble retention field. No-tillage practice significantly increased the weed species diversity under winter wheat phase and decreased the diversity under common vetch phase. At maize phase, a greater species diversity index was observed in the no-tillage field. These results suggested that no-tillage practice and stubble retention possibly suppress specific weeds with the presence of some crops and crop rotation is a vital way to controlling weeds in a farming system.

Robust Crop and Weed Segmentation under Uncontrolled Outdoor Illumination

PubMed Central

Jeon, Hong Y.; Tian, Lei F.; Zhu, Heping

2011-01-01

An image processing algorithm for detecting individual weeds was developed and evaluated. Weed detection processes included were normalized excessive green conversion, statistical threshold value estimation, adaptive image segmentation, median filter, morphological feature calculation and Artificial Neural Network (ANN). The developed algorithm was validated for its ability to identify and detect weeds and crop plants under uncontrolled outdoor illuminations. A machine vision implementing field robot captured field images under outdoor illuminations and the image processing algorithm automatically processed them without manual adjustment. The errors of the algorithm, when processing 666 field images, ranged from 2.1 to 2.9%. The ANN correctly detected 72.6% of crop plants from the identified plants, and considered the rest as weeds. However, the ANN identification rates for crop plants were improved up to 95.1% by addressing the error sources in the algorithm. The developed weed detection and image processing algorithm provides a novel method to identify plants against soil background under the uncontrolled outdoor illuminations, and to differentiate weeds from crop plants. Thus, the proposed new machine vision and processing algorithm may be useful for outdoor applications including plant specific direct applications (PSDA). PMID:22163954

Organic weed conrol and cover crop residue integration impacts on weed control, quality, and yield and economics in conservation tillage tomato - A case study

USDA-ARS?s Scientific Manuscript database

The increased use of conservation tillage in vegetable production requires more information be developed on the role of cover crops in weed control, tomato quality and yield. Three conservation-tillage systems utilizing crimson clover, brassica and cereal rye as winter cover crops were compared to ...

Weed control in organic rice using plastic mulch and water seeding methods in addition to cover crops

USDA-ARS?s Scientific Manuscript database

Weeds are a major yield limiting factor in organic rice farming and are more problematic than in conventional production systems. Water seeding is a common method of reducing weed pressure in rice fields as many weeds connot tolerate flooded field conditions. The use of cover crops is another method...

The role of plant-microbiome interactions in weed establishment and control.

PubMed

Trognitz, Friederike; Hackl, Evelyn; Widhalm, Siegrid; Sessitsch, Angela

2016-10-01

The soil microbiome plays an important role in the establishment of weeds and invasive plants. They associate with microorganisms supporting their growth and health. Weed management strategies, like tillage and herbicide treatments, to control weeds generally alter soil structure going alongside with changes in the microbial community. Once a weed population establishes in the field, the plants build up a close relationship with the available microorganisms. Seeds or vegetative organs overwinter in soil and select early in the season their own microbiome before crop plants start to vegetate. Weed and crop plants compete for light, nutrition and water, but may differently interact with soil microorganisms. The development of new sequencing technologies for analyzing soil microbiomes has opened up the possibility for in depth analysis of the interaction between 'undesired' plants and crop plants under different management systems. These findings will help us to understand the functions of microorganisms involved in crop productivity and plant health, weed establishment and weed prevention. Exploitation of the knowledge offers the possibility to search for new biocontrol methods against weeds based on soil and plant-associated microorganisms. This review discusses the recent advances in understanding the functions of microbial communities for weed/invasive plant establishment and shows new ways to use plant-associated microorganisms to control weeds and invasive plants in different land management systems. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

IMI resistance associated to crop-weed hybridization in a natural Brassica rapa population: characterization and fate.

PubMed

Ureta, M S; Torres Carbonell, F; Pandolfo, C; Presotto, A D; Cantamutto, M A; Poverene, M

2017-03-01

Wild turnip (Brassica rapa) is a common weed and a close relative to oilseed rape (Brassica napus). The Clearfield® production system is a highly adopted tool which provides an alternative solution for weed management, but its efficiency is threatened by gene transfer from crop to weed relatives. Crop-weed hybrids with herbicide resistance were found in the progeny of a B. rapa population gathered from a weedy stand on the borders of an oilseed rape (B. napus) imidazolinone (IMI)-resistant crop. Interspecific hybrids were confirmed by morphological traits in the greenhouse and experimental field, survival after imazethapyr applications, DNA content through flow cytometry, and pollen viability. The transference of herbicide resistance was demonstrated even in a particular situation of pollen competition between both an herbicide-resistant crop and a non-resistant crop. However, IMI resistance was not found in further generations collected at the same location. These results verify gene transmission from oilseed rape to B. rapa in the main crop area in Argentina where resistant and susceptible varieties are found and seed loss and crop volunteers are common. Hybridization, introgression, and herbicide selection would be associated with the loss of effectiveness of IMI technology.

The Effect of Conservation Tillage and Cover Crop Residue on Beneficial Arthropods and Weed Seed Predation in Acorn Squash.

PubMed

Quinn, N F; Brainard, D C; Szendrei, Z

2016-12-01

Conservation tillage combined with cover crops or mulching may enhance natural enemy activity in agroecosystems by reducing soil disturbance and increasing habitat structural complexity. In particular, weed seed predation can increase with vegetation cover and reduced tillage, indicating that mulches may improve the quality of the habitat for weed seed foraging. The purpose of this study was to quantify the effects of tillage and mulching for conservation biological control in cucurbit fields. The effects of mulch and reduced tillage on arthropods and rates of weed seed loss from arenas were examined in field trials on sandy soils in 2014 and 2015. Experimental factors included tillage and cover crop, each with two levels: strip-tillage or full-tillage, and cover crop mulch (rye residue) or no cover crop mulch (unmulched). Arthropod abundance on the crop foliage was not affected by tillage or cover crops. Contrary to expectations, epigeal natural enemies of insects and rates of weed seed removal either did not respond to treatments or were greater in full-tilled plots and plots without mulch. Our study demonstrates the potential importance of weed seed predators in reducing weed seedbanks in vegetable agroecosystems, and suggests that early-season tillage may not be detrimental to epigeal predator assemblages. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

United States Department of Agriculture-Agricultural Research Service research on pest biology: weeds.

PubMed

Forcella, Frank

2003-01-01

Over 125 permanent full-time scientists conduct research within the USDA Agricultural Research Service (ARS) on issues related to weeds. The research emphasis of most of these scientists involves ecology and management or biological control of weeds. Many scientists perform research on weed biology as components of their primary projects on weed control and integrated crop and soil management. Describing all ARS projects involved with weed biology is impossible, and consequently only research that falls within the following arbitrarily chosen topics is highlighted in this article: dormancy mechanisms; cell division; diversity of rangeland weeds; soil resources and rangeland weeds; poisonous rangeland plants; horticultural weeds; weed traits limiting chemical control; aquatic and semi-aquatic weeds; weed/transgenic wheat hybrids; seedbanks, seedling emergence and seedling populations; and weed seed production. Within these topics, and others not highlighted, the desire of ARS is that good information on weed biology currently translates or eventually will translate into practical advice for those who must manage weeds.

Effect of weed management and seed rate on crop growth under direct dry seeded rice systems in Bangladesh.

PubMed

Ahmed, Sharif; Salim, Muhammad; Chauhan, Bhagirath S

2014-01-01

Weeds are a major constraint to the success of dry-seeded rice (DSR). The main means of managing these in a DSR system is through chemical weed control using herbicides. However, the use of herbicides alone may not be sustainable in the long term. Approaches that aim for high crop competitiveness therefore need to be exploited. One such approach is the use of high rice seeding rates. Experiments were conducted in the aman (wet) seasons of 2012 and 2013 in Bangladesh to evaluate the effect of weed infestation level (partially-weedy and weed-free) and rice seeding rate (20, 40, 60, 80, and 100 kg ha(-1)) on weed and crop growth in DSR. Under weed-free conditions, higher crop yields (5.1 and 5.2 t ha(-1) in the 2012 and 2013 seasons, respectively) were obtained at the seeding rate of 40 kg ha(-1) and thereafter, yield decreased slightly beyond 40 kg seed ha(-1). Under partially-weedy conditions, yield increased by 30 to 33% (2.0-2.2 and 2.9-3.2 t ha(-1) in the 2012 and 2013 seasons, respectively) with increase in seeding rate from 20 to 100 kg ha(-1). In the partially-weedy plots, weed biomass decreased by 41-60% and 54-56% at 35 days after sowing and at crop anthesis, respectively, when seeding rate increased from 20 to 100 kg ha(-1). Results from our study suggest that increasing seeding rates in DSR can suppress weed growth and reduce grain yield losses from weed competition.

Herbicides do not ensure for higher wheat yield, but eliminate rare plant species

PubMed Central

Gaba, Sabrina; Gabriel, Edith; Chadœuf, Joël; Bonneu, Florent; Bretagnolle, Vincent

2016-01-01

Weed control is generally considered to be essential for crop production and herbicides have become the main method used for weed control in developed countries. However, concerns about harmful environmental consequences have led to strong pressure on farmers to reduce the use of herbicides. As food demand is forecast to increase by 50% over the next century, an in-depth quantitative analysis of crop yields, weeds and herbicides is required to balance economic and environmental issues. This study analysed the relationship between weeds, herbicides and winter wheat yields using data from 150 winter wheat fields in western France. A Bayesian hierarchical model was built to take account of farmers’ behaviour, including implicitly their perception of weeds and weed control practices, on the effectiveness of treatment. No relationship was detected between crop yields and herbicide use. Herbicides were found to be more effective at controlling rare plant species than abundant weed species. These results suggest that reducing the use of herbicides by up to 50% could maintain crop production, a result confirmed by previous studies, while encouraging weed biodiversity. Food security and biodiversity conservation may, therefore, be achieved simultaneously in intensive agriculture simply by reducing the use of herbicides. PMID:27453451

Development and Testing of a Decision Making Based Method to Adjust Automatically the Harrowing Intensity

PubMed Central

Rueda-Ayala, Victor; Weis, Martin; Keller, Martina; Andújar, Dionisio; Gerhards, Roland

2013-01-01

Harrowing is often used to reduce weed competition, generally using a constant intensity across a whole field. The efficacy of weed harrowing in wheat and barley can be optimized, if site-specific conditions of soil, weed infestation and crop growth stage are taken into account. This study aimed to develop and test an algorithm to automatically adjust the harrowing intensity by varying the tine angle and number of passes. The field variability of crop leaf cover, weed density and soil density was acquired with geo-referenced sensors to investigate the harrowing selectivity and crop recovery. Crop leaf cover and weed density were assessed using bispectral cameras through differential images analysis. The draught force of the soil opposite to the direction of travel was measured with electronic load cell sensor connected to a rigid tine mounted in front of the harrow. Optimal harrowing intensity levels were derived in previously implemented experiments, based on the weed control efficacy and yield gain. The assessments of crop leaf cover, weed density and soil density were combined via rules with the aforementioned optimal intensities, in a linguistic fuzzy inference system (LFIS). The system was evaluated in two field experiments that compared constant intensities with variable intensities inferred by the system. A higher weed density reduction could be achieved when the harrowing intensity was not kept constant along the cultivated plot. Varying the intensity tended to reduce the crop leaf cover, though slightly improving crop yield. A real-time intensity adjustment with this system is achievable, if the cameras are attached in the front and at the rear or sides of the harrow. PMID:23669712

Using thermal units for estimating critical period of weed competition in off-season maize crop.

PubMed

López-Ovejero, Ramiro Fernando; y Garcia, Axel Garcia; de Carvalho, Saul Jorge P; Christoffoleti, Pedro J; Neto, Durval Dourado; Martins, Fernando; Nicolai, Marcelo

2005-01-01

Brazilian off-season maize production is characterized by low yield due to several factors, such as climate variability and inadequate management practices, specifically weed management. Thus, the goal of this study was to determinate the critical period of weed competition in off-season maize (Zea mays L.) crop using thermal units or growing degree days (GDD) approach to characterize crop growth and development. The study was carried out in experimental area of the University of São Paulo, Brazil, with weed control (C), as well as seven coexistence periods, 2, 4, 6, 8, and 12 leaves, flowering, and all crop cycle; fourteen treatments were done. Climate data were obtained from a weather station located close to the experimental area. To determine the critical period for weed control (CPWC) logistic models were fitted to yield data obtained in both W and C, as a function of GDD. For an arbitrary maximum yield loss fixed in 2.5%, the CPWC was found between 301 and 484 GDD (7-8 leaves). Also, when the arbitrary loss yield was fixed in 5 and 10%, the period before interference (PBI) was higher than the critical weed-free period (CWFP), suggesting that the weeds control can be done with only one application, between 144 and 410 GDD and 131 and 444 GDD (3-8 leaves), respectively. The GDD approach to characterize crop growth and development was successfully used to determine the critical period of weeds control in maize sown off-season. Further works will be necessary to better characterize the interaction and complexity of maize sown off-season with weeds. However, these results are encouraging because the possibility of the results to be extrapolated and because the potential of the method on providing important results to researchers, specifically crop modelers.

Combining functional weed ecology and crop stable isotope ratios to identify cultivation intensity: a comparison of cereal production regimes in Haute Provence, France and Asturias, Spain.

PubMed

Bogaard, Amy; Hodgson, John; Nitsch, Erika; Jones, Glynis; Styring, Amy; Diffey, Charlotte; Pouncett, John; Herbig, Christoph; Charles, Michael; Ertuğ, Füsun; Tugay, Osman; Filipovic, Dragana; Fraser, Rebecca

This investigation combines two independent methods of identifying crop growing conditions and husbandry practices-functional weed ecology and crop stable carbon and nitrogen isotope analysis-in order to assess their potential for inferring the intensity of past cereal production systems using archaeobotanical assemblages. Present-day organic cereal farming in Haute Provence, France features crop varieties adapted to low-nutrient soils managed through crop rotation, with little to no manuring. Weed quadrat survey of 60 crop field transects in this region revealed that floristic variation primarily reflects geographical differences. Functional ecological weed data clearly distinguish the Provence fields from those surveyed in a previous study of intensively managed spelt wheat in Asturias, north-western Spain: as expected, weed ecological data reflect higher soil fertility and disturbance in Asturias. Similarly, crop stable nitrogen isotope values distinguish between intensive manuring in Asturias and long-term cultivation with minimal manuring in Haute Provence. The new model of cereal cultivation intensity based on weed ecology and crop isotope values in Haute Provence and Asturias was tested through application to two other present-day regimes, successfully identifying a high-intensity regime in the Sighisoara region, Romania, and low-intensity production in Kastamonu, Turkey. Application of this new model to Neolithic archaeobotanical assemblages in central Europe suggests that early farming tended to be intensive, and likely incorporated manuring, but also exhibited considerable variation, providing a finer grained understanding of cultivation intensity than previously available.

Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition.

PubMed

Andrew, Izzadora K S; Storkey, Jonathan

2017-05-01

With the increasing pressure on crop production from the evolution of herbicide resistance, farmers are increasingly adopting Integrated Weed Management (IWM) strategies to augment their weed control. These include measures to increase the competitiveness of the crop canopy such as increased sowing rate and the use of more competitive cultivars. While there are data on the relative impact of these non-chemical weed control methods assessed in isolation, there is uncertainty about their combined contribution, which may be hindering their adoption. In this article, the INTERCOM simulation model of crop/weed competition was used to examine the combined impact of crop density, sowing date and cultivar choice on the outcomes of competition between wheat ( Triticum aestivum ) and Alopecurus myosuroides . Alopecurus myosuroides is a problematic weed of cereal crops in North-Western Europe and the primary target for IWM in the UK because it has evolved resistance to a range of herbicides. The model was parameterised for two cultivars with contrasting competitive ability, and simulations run across 10 years at different crop densities and two sowing dates. The results suggest that sowing date, sowing density and cultivar choice largely work in a complementary fashion, allowing enhanced competitive ability against weeds when used in combination. However, the relative benefit of choosing a more competitive cultivar decreases at later sowing dates and higher crop densities. Modeling approaches could be further employed to examine the effectiveness of IWM, reducing the need for more expensive and cumbersome long-term in situ experimentation.

Tracing back seed and pollen flow within the crop-wild Beta vulgaris complex: genetic distinctiveness vs. hot spots of hybridization over a regional scale.

PubMed

Viard, Frédérique; Arnaud, Jean-François; Delescluse, Maxime; Cuguen, Joël

2004-06-01

Hybrids between transgenic crops and wild relatives have been documented successfully in a wide range of cultivated species, having implications on conservation and biosafety management. Nonetheless, the magnitude and frequency of hybridization in the wild is still an open question, in particular when considering several populations at the landscape level. The Beta vulgaris complex provides an excellent biological model to tackle this issue. Weed beets contaminating sugar beet fields are expected to act as a relay between wild populations and crops and from crops-to-crops. In one major European sugar beet production area, nine wild populations and 12 weed populations were genetically characterized using cytoplasmic markers specific to the cultivated lines and nuclear microsatellite loci. A tremendous overall genetic differentiation between neighbouring wild and weed populations was depicted. However, genetic admixture analyses at the individual level revealed clear evidence for gene flow between wild and weed populations. In particular, one wild population displayed a high magnitude of nuclear genetic admixture, reinforced by direct seed flow as evidenced by cytoplasmic markers. Altogether, weed beets were shown to act as relay for gene flow between crops to wild populations and crops to crops by pollen and seeds at a landscape level.

Effect of Weed Management and Seed Rate on Crop Growth under Direct Dry Seeded Rice Systems in Bangladesh

PubMed Central

Ahmed, Sharif; Salim, Muhammad; Chauhan, Bhagirath S.

2014-01-01

Weeds are a major constraint to the success of dry-seeded rice (DSR). The main means of managing these in a DSR system is through chemical weed control using herbicides. However, the use of herbicides alone may not be sustainable in the long term. Approaches that aim for high crop competitiveness therefore need to be exploited. One such approach is the use of high rice seeding rates. Experiments were conducted in the aman (wet) seasons of 2012 and 2013 in Bangladesh to evaluate the effect of weed infestation level (partially-weedy and weed-free) and rice seeding rate (20, 40, 60, 80, and 100 kg ha−1) on weed and crop growth in DSR. Under weed-free conditions, higher crop yields (5.1 and 5.2 t ha−1 in the 2012 and 2013 seasons, respectively) were obtained at the seeding rate of 40 kg ha−1 and thereafter, yield decreased slightly beyond 40 kg seed ha−1. Under partially-weedy conditions, yield increased by 30 to 33% (2.0–2.2 and 2.9–3.2 t ha−1 in the 2012 and 2013 seasons, respectively) with increase in seeding rate from 20 to 100 kg ha−1. In the partially-weedy plots, weed biomass decreased by 41–60% and 54–56% at 35 days after sowing and at crop anthesis, respectively, when seeding rate increased from 20 to 100 kg ha−1. Results from our study suggest that increasing seeding rates in DSR can suppress weed growth and reduce grain yield losses from weed competition. PMID:25000520

Benchmark study on glyphosate-resistant crop systems in the United States. Economics of herbicide resistance management practices in a 5 year field-scale study.

PubMed

Edwards, C Blake; Jordan, David L; Owen, Michael Dk; Dixon, Philip M; Young, Bryan G; Wilson, Robert G; Weller, Steven C; Shaw, David R

2014-12-01

Since the introduction of glyphosate-resistant (GR) crops, growers have often relied on glyphosate-only weed control programs. As a result, multiple weeds have evolved resistance to glyphosate. A 5 year study including 156 growers from Illinois, Iowa, Indiana, Nebraska, North Carolina and Mississippi in the United States was conducted to compare crop yields and net returns between grower standard weed management programs (SPs) and programs containing best management practices (BMPs) recommended by university weed scientists. The BMPs were designed to prevent or mitigate/manage evolved herbicide resistance. Weed management costs were greater for the BMP approach in most situations, but crop yields often increased sufficiently for net returns similar to those of the less expensive SPs. This response was similar across all years, geographical regions, states, crops and tillage systems. Herbicide use strategies that include a diversity of herbicide mechanisms of action will increase the long-term sustainability of glyphosate-based weed management strategies. Growers can adopt herbicide resistance BMPs with confidence that net returns will not be negatively affected in the short term and contribute to resistance management in the long term. © 2014 Society of Chemical Industry.

Tillage and planting date effects on weed dormancy, emergence, and early growth in organic corn

USDA-ARS?s Scientific Manuscript database

Weed management is a major constraint to adoption of reduced-tillage practices for organic grain production. Tillage, cover crop management, and crop planting date are all factors that influence the periodicity and growth potential of important weed species in these systems. Therefore, we assessed...

Fates of Setaria faberi and Abutilon theophrasti seeds in three crop rotation systems

USDA-ARS?s Scientific Manuscript database

Weed seeds in and on the soil are the primary cause of weed infestations in arable fields. Previous studies have documented reductions in weed seedbanks due to cropping system diversification through extended rotation sequences, but the impacts of different rotation systems on additions to and losse...

Purple nutsedge (Cyperus rotundus) tuber production and viability is reduced by imazapic

USDA-ARS?s Scientific Manuscript database

Weeds exploit underutilized space, causing economic losses in cropping systems. Weed management tactics alter that underutilized space until the crop can mature and efficiently use that space. One tactic is to reduce the weed populations that persist quiescent in the soil, including minimizing pro...

Weed seed persistence and microbial abundance in long-term organic and conventional cropping systems

USDA-ARS?s Scientific Manuscript database

Weed seed persistence in soil can be influenced by many factors, including crop management. This research was conducted to determine whether organic management systems with higher organic amendments and soil microbial biomass could reduce weed seed persistence compared to conventional management sy...

The mechanism for weed suppression by a forage radish cover crop

USDA-ARS?s Scientific Manuscript database

In the Mid-Atlantic region, forage radish (Raphanus sativus L. var. longipinnatus) winter cover crops planted prior to 1 September suppress winter annual weeds from fall until early April. Little is known about the mechanism of this weed suppression. Published research reports suggest that allelopat...

Subplots facilitate assessment of corn yield losses from weed competition in a long-term systems experiment

USDA-ARS?s Scientific Manuscript database

Weeds can potentially limit crop yield, particularly in organic systems where herbicide technologies are unavailable. Weedy and weed-free subplots were established within full plots of a long-term cropping systems experiment, the Farming Systems Project, at Beltsville, Maryland, USA, to determine t...

Host-Plant Selectivity of Rhizobacteria in a Crop/Weed Model System

PubMed Central

Zeller, Simon L.; Brandl, Helmut; Schmid, Bernhard

2007-01-01

Belowground microorganisms are known to influence plants' performance by altering the soil environment. Plant pathogens such as cyanide-producing strains of the rhizobacterium Pseudomonas may show strong host-plant selectivity. We analyzed interactions between different host plants and Pseudomonas strains and tested if these can be linked to the cyanide sensitivity of host plants, the cyanide production of bacterial strains or the plant identity from which strains had been isolated. Eight strains (four cyanide producing) were isolated from roots of four weed species and then re-inoculated on the four weed and two additional crop species. Bacterial strain composition varied strongly among the four weed species. Although all six plant species showed different reductions in root growth when cyanide was artificially applied to seedlings, they were generally not negatively affected by inoculation with cyanide-producing bacterial strains. We found a highly significant plant species x bacterial strain interaction. Partitioning this interaction into contrasts showed that it was entirely due to a strongly negative effect of a bacterial strain (Pseudomonas kilonensis/brassicacearum, isolated from Galium mollugo) on Echinochloa crus-galli. This exotic weed may not have become adapted to the bacterial strain isolated from a native weed. Our findings suggest that host-specific rhizobacteria hold some promise as biological weed-control agents. PMID:17786217

Biotechnology in weed control

USDA-ARS?s Scientific Manuscript database

Biotechnology can be used to enhance the management of weeds in several ways. Crops have been made resistant to herbicides by inserting transgenes that impart herbicide resistance into the plant genome. Glyphosate and glufosinate-resistant crops are commercialized in North America and crops made res...

Combining spatial and spectral information to improve crop/weed discrimination algorithms

NASA Astrophysics Data System (ADS)

Yan, L.; Jones, G.; Villette, S.; Paoli, J. N.; Gée, C.

2012-01-01

Reduction of herbicide spraying is an important key to environmentally and economically improve weed management. To achieve this, remote sensors such as imaging systems are commonly used to detect weed plants. We developed spatial algorithms that detect the crop rows to discriminate crop from weeds. These algorithms have been thoroughly tested and provide robust and accurate results without learning process but their detection is limited to inter-row areas. Crop/Weed discrimination using spectral information is able to detect intra-row weeds but generally needs a prior learning process. We propose a method based on spatial and spectral information to enhance the discrimination and overcome the limitations of both algorithms. The classification from the spatial algorithm is used to build the training set for the spectral discrimination method. With this approach we are able to improve the range of weed detection in the entire field (inter and intra-row). To test the efficiency of these algorithms, a relevant database of virtual images issued from SimAField model has been used and combined to LOPEX93 spectral database. The developed method based is evaluated and compared with the initial method in this paper and shows an important enhancement from 86% of weed detection to more than 95%.

The red queen in the corn: agricultural weeds as models of rapid adaptive evolution.

PubMed

Vigueira, C C; Olsen, K M; Caicedo, A L

2013-04-01

Weeds are among the greatest pests of agriculture, causing billions of dollars in crop losses each year. As crop field management practices have changed over the past 12 000 years, weeds have adapted in turn to evade human removal. This evolutionary change can be startlingly rapid, making weeds an appealing system to study evolutionary processes that occur over short periods of time. An understanding of how weeds originate and adapt is needed for successful management; however, relatively little emphasis has been placed on genetically characterizing these systems. Here, we review the current literature on agricultural weed origins and their mechanisms of adaptation. Where possible, we have included examples that have been genetically well characterized. Evidence for three possible, non-mutually exclusive weed origins (from wild species, crop-wild hybrids or directly from crops) is discussed with respect to what is known about the microevolutionary signatures that result from these processes. We also discuss what is known about the genetic basis of adaptive traits in weeds and the range of genetic mechanisms that are responsible. With a better understanding of genetic mechanisms underlying adaptation in weedy species, we can address the more general process of adaptive evolution and what can be expected as we continue to apply selective pressures in agroecosystems around the world.

The red queen in the corn: agricultural weeds as models of rapid adaptive evolution

PubMed Central

Vigueira, C C; Olsen, K M; Caicedo, A L

2013-01-01

Weeds are among the greatest pests of agriculture, causing billions of dollars in crop losses each year. As crop field management practices have changed over the past 12 000 years, weeds have adapted in turn to evade human removal. This evolutionary change can be startlingly rapid, making weeds an appealing system to study evolutionary processes that occur over short periods of time. An understanding of how weeds originate and adapt is needed for successful management; however, relatively little emphasis has been placed on genetically characterizing these systems. Here, we review the current literature on agricultural weed origins and their mechanisms of adaptation. Where possible, we have included examples that have been genetically well characterized. Evidence for three possible, non-mutually exclusive weed origins (from wild species, crop-wild hybrids or directly from crops) is discussed with respect to what is known about the microevolutionary signatures that result from these processes. We also discuss what is known about the genetic basis of adaptive traits in weeds and the range of genetic mechanisms that are responsible. With a better understanding of genetic mechanisms underlying adaptation in weedy species, we can address the more general process of adaptive evolution and what can be expected as we continue to apply selective pressures in agroecosystems around the world. PMID:23188175

Biology and management of Avena fatua and Avena ludoviciana: two noxious weed species of agro-ecosystems.

PubMed

Bajwa, Ali Ahsan; Akhter, Muhammad Javaid; Iqbal, Nadeem; Peerzada, Arslan Masood; Hanif, Zarka; Manalil, Sudheesh; Hashim, Saima; Ali, Hafiz Haider; Kebaso, Lynda; Frimpong, David; Namubiru, Halima; Chauhan, Bhagirath Singh

2017-08-01

Avena fatua and Avena ludoviciana are closely related grass weed species infesting a large number of crops around the world. These species are widely distributed in diverse agro-ecosystems from temperate to sub-tropical regions due to their unique seed traits, successful germination ecology, high competitive ability, and allelopathic potential. A. fatua is more widespread, adaptable, and problematic than A. ludoviciana. Both these species infest major winter and spring crops, including wheat, oat, barley, canola, maize, alfalfa, and sunflower, causing up to 70% yield losses depending on crop species and weed density. Chemical control has been challenged by large-scale herbicide resistance evolution in these weed species. A. fatua is the most widespread herbicide-resistant weed in the world, infesting about 5 million hectares in 13 countries. The use of alternative herbicides with different modes of action has proved effective. Several cultural practices, including diverse crop rotations, cover crops, improved crop competition (using competitive cultivars, high seed rates, narrow row spacing, altered crop geometry), and allelopathic suppression, have shown promise for controlling A. fatua and A. ludoviciana. The integrated use of these cultural methods can reduce the herbicide dose required, and lower dependency on herbicides to control these grasses. Moreover, integrated management may successfully control herbicide-resistant populations of these weed species. The use of integrated approaches based on the knowledge of biology and ecology of A. fatua and A. ludoviciana may help to manage them sustainably in the future.

Quantifying temporal isolation: a modelling approach assessing the effect of flowering time differences on crop-to-weed pollen flow in sunflower

PubMed Central

Roumet, Marie; Cayre, Adeline; Latreille, Muriel; Muller, Marie-Hélène

2015-01-01

Flowering time divergence can be a crucial component of reproductive isolation between sympatric populations, but few studies have quantified its actual contribution to the reduction of gene flow. In this study, we aimed at estimating pollen-mediated gene flow between cultivated sunflower and a weedy conspecific sunflower population growing in the same field and at quantifying, how it is affected by the weeds' flowering time. For that purpose, we extended an existing mating model by including a temporal distance (i.e. flowering time difference between potential parents) effect on mating probabilities. Using phenological and genotypic data gathered on the crop and on a sample of the weedy population and its offspring, we estimated an average hybridization rate of approximately 10%. This rate varied strongly from 30% on average for weeds flowering at the crop flowering peak to 0% when the crop finished flowering and was affected by the local density of weeds. Our result also suggested the occurrence of other factors limiting crop-to-weed gene flow. This level of gene flow and its dependence on flowering time might influence the evolutionary fate of weedy sunflower populations sympatric to their crop relative. PMID:25667603

A non-chemical system for online weed control.

PubMed

Rueda-Ayala, Victor; Peteinatos, Gerassimos; Gerhards, Roland; Andújar, Dionisio

2015-03-30

Non-chemical weed control methods need to be directed towards a site-specific weeding approach, in order to be able to compete the conventional herbicide equivalents. A system for online weed control was developed. It automatically adjusts the tine angle of a harrow and creates different levels of intensity: from gentle to aggressive. Two experimental plots in a maize field were harrowed with two consecutive passes. The plots presented from low to high weed infestation levels. Discriminant capabilities of an ultrasonic sensor were used to determine the crop and weed variability of the field. A controlling unit used ultrasonic readings to adjust the tine angle, producing an appropriate harrowing intensity. Thus, areas with high crop and weed densities were more aggressively harrowed, while areas with lower densities were cultivated with a gentler treatment; areas with very low densities or without weeds were not treated. Although the weed development was relatively advanced and the soil surface was hard, the weed control achieved by the system reached an average of 51% (20%-91%), without causing significant crop damage as a result of harrowing. This system is proposed as a relatively low cost, online, and real-time automatic harrow that improves the weed control efficacy, reduces energy consumption, and avoids the usage of herbicide.

A Non-Chemical System for Online Weed Control

PubMed Central

Rueda-Ayala, Victor; Peteinatos, Gerassimos; Gerhards, Roland; Andújar, Dionisio

2015-01-01

Non-chemical weed control methods need to be directed towards a site-specific weeding approach, in order to be able to compete the conventional herbicide equivalents. A system for online weed control was developed. It automatically adjusts the tine angle of a harrow and creates different levels of intensity: from gentle to aggressive. Two experimental plots in a maize field were harrowed with two consecutive passes. The plots presented from low to high weed infestation levels. Discriminant capabilities of an ultrasonic sensor were used to determine the crop and weed variability of the field. A controlling unit used ultrasonic readings to adjust the tine angle, producing an appropriate harrowing intensity. Thus, areas with high crop and weed densities were more aggressively harrowed, while areas with lower densities were cultivated with a gentler treatment; areas with very low densities or without weeds were not treated. Although the weed development was relatively advanced and the soil surface was hard, the weed control achieved by the system reached an average of 51% (20%–91%), without causing significant crop damage as a result of harrowing. This system is proposed as a relatively low cost, online, and real-time automatic harrow that improves the weed control efficacy, reduces energy consumption, and avoids the usage of herbicide. PMID:25831085

Factors affecting potential for Palmer amaranth (Amaranthus palmeri) suppression by winter rye in Georgia, USA

USDA-ARS?s Scientific Manuscript database

Herbicide resistant Palmer amaranth has rapidly become a dominant weed management issue in agronomic crops of the Southeast U. S. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-biomass, rolled cover crop mul...

Evaluation of tillage, cover crop, and herbicide effects on weed control, yield, and grade in peanut

USDA-ARS?s Scientific Manuscript database

Peanut production plays a large role in agriculture in the Southeastern United States. Weeds are detrimental to their production because of the competition that they create; weeds will compete with crops for resources such as nutrients and sunlight, among others. Therefore, it is important to reduce...

Role of herbicide-resistant crops in integrated weed management

USDA-ARS?s Scientific Manuscript database

Chemical weed control began with the use of 2,4-D in the mid-1940s. Since then, a wide array of herbicides has been commercialized and that has greatly contributed to increased crop yields. With the introduction of several new, more specific and more effective herbicides, the cost of weed control wi...

A novel 5-enolpyruvoylshikimate-3-phosphate (EPSP) synthase transgene for glyphosate resistance stimulates growth and fecundity in weedy rice (Oryza sativa) without herbicide.

PubMed

Wang, Wei; Xia, Hui; Yang, Xiao; Xu, Ting; Si, Hong Jiang; Cai, Xing Xing; Wang, Feng; Su, Jun; Snow, Allison A; Lu, Bao-Rong

2014-04-01

Understanding evolutionary interactions among crops and weeds can facilitate effective weed management. For example, gene flow from crops to their wild or weedy relatives can lead to rapid evolution in recipient populations. In rice (Oryza sativa), transgenic herbicide resistance is expected to spread to conspecific weedy rice (Oryza sativa f. spontanea) via hybridization. Here, we studied fitness effects of transgenic over-expression of a native 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) gene developed to confer glyphosate resistance in rice. Controlling for genetic background, we examined physiological traits and field performance of crop-weed hybrid lineages that segregated for the presence or absence of this novel epsps transgene. Surprisingly, we found that transgenic F2 crop-weed hybrids produced 48-125% more seeds per plant than nontransgenic controls in monoculture- and mixed-planting designs without glyphosate application. Transgenic plants also had greater EPSPS protein levels, tryptophan concentrations, photosynthetic rates, and per cent seed germination compared with nontransgenic controls. Our findings suggest that over-expression of a native rice epsps gene can lead to fitness advantages, even without exposure to glyphosate. We hypothesize that over-expressed epsps may be useful to breeders and, if deployed, could result in fitness benefits in weedy relatives following transgene introgression. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Exploitation of allelopathy for weed control in annual and perennial cropping systems.

PubMed

Putnam, A R; Defrank, J; Barnes, J P

1983-08-01

A variety of crops, cultivars, and accessions have been evaluated over the past six years for superior capability to suppress weed growth. The most successful of these approaches has been to grow cover crops of rye (Secale cereale), wheat (Triticum aestivum), sorghum (Sorghum bicolor), or barley (Hordeum vulgare) to a height of 40-50 cm, desiccate the crops by contact herbicides or freezing, and allow their residues to remain on the soil surface. Often, up to 95% control of important agroecosystem weed species was obtained for a 30- to 60-day period following desiccation of the cover crop. The plant residues on the soil surface exhibit numerous physical and chemical attributes that contribute to weed suppression. Physical aspects include shading and reduced soil temperatures which were similarly achieved using poplar (Populus) excelsior as a control mulch. Chemical aspects apparently include direct release of toxins, as well as production of phytotoxic microbial products. Numerous chemicals appear to work in concert or in an additive or synergistic manner to reduce weed germination and growth.

Improved discrimination between monocotyledonous and dicotyledonous plants for weed control based on the blue-green region of ultraviolet-induced fluorescence spectra.

PubMed

Panneton, Bernard; Guillaume, Serge; Roger, Jean-Michel; Samson, Guy

2010-01-01

Precision weeding by spot spraying in real time requires sensors to discriminate between weeds and crop without contact. Among the optical based solutions, the ultraviolet (UV) induced fluorescence of the plants appears as a promising alternative. In a first paper, the feasibility of discriminating between corn hybrids, monocotyledonous, and dicotyledonous weeds was demonstrated on the basis of the complete spectra. Some considerations about the different sources of fluorescence oriented the focus to the blue-green fluorescence (BGF) part, ignoring the chlorophyll fluorescence that is inherently more variable in time. This paper investigates the potential of performing weed/crop discrimination on the basis of several large spectral bands in the BGF area. A partial least squares discriminant analysis (PLS-DA) was performed on a set of 1908 spectra of corn and weed plants over 3 years and various growing conditions. The discrimination between monocotyledonous and dicotyledonous plants based on the blue-green fluorescence yielded robust models (classification error between 1.3 and 4.6% for between-year validation). On the basis of the analysis of the PLS-DA model, two large bands were chosen in the blue-green fluorescence zone (400-425 nm and 425-490 nm). A linear discriminant analysis based on the signal from these two bands also provided very robust inter-year results (classification error from 1.5% to 5.2%). The same selection process was applied to discriminate between monocotyledonous weeds and maize but yielded no robust models (up to 50% inter-year error). Further work will be required to solve this problem and provide a complete UV fluorescence based sensor for weed-maize discrimination.

[Species, Damage and Community Structure of Weeds in Scrophularia ningpoensis Fields in Nanchuan, Chongqing].

PubMed

Han, Feng; Xiao, Jie-yi; Cao, Hou-qiang; Luo, Chuan; Yang, Tian-jian; Lin, Mao-xiang

2015-10-01

To investigate the damage and community structure of weeds in Scrophularia ningpoensis fields in Nanchuan, Chongqing. From 2013 to 2014, an investigation was carried out by inverted W-9 point sampling method to study the weed species. 96 weed species belonged to 75 genera of 30 families were observed, including 18 species of Asteraceae weeds (accounted for 18.75%), 10 species of Poaceae weeds (accounted for 10.42%). Moreover, there were 57 species of annual weeds (accounted for 59.38%) and 39 species of perennial weeds (accounted for 40.63%). The overall abundance of Erigeron annuus, Digitaria adscendens, Torilis scabra, Polygonum nepalense, Ranunculus japonicas, Stellaria media and Commelina communis were relatively higher than that of the others. The difference of weed species and community structure might result from the physical and chemical characteristics of soil, moisture content, cropping system, tillage type, environmental and climatic conditions, crop distribution and weed control.

Comperative investigations of non chemical weed management methods in Hungary.

PubMed

Pali, Orsolya; Reisinger, Peter; Pomsar, Peter

2007-01-01

Organic farming has an increasing tendency in Hungary because of growing consumers' demands according to organic products not only in inland but also in the countries of the European Union. Developments of weed control methods in organically cropped field plants have become conspicuous next to developing chemical weed management methods of convencionally cropped cultural plants. The aim of our investigations was to make comperative investigations of non chemical weed control methods in wide rowed plants.

Crop biomass not species richness drives weed suppression in warm-season annual grass-legume intercrops in the Northeast

USDA-ARS?s Scientific Manuscript database

Intercropping with functionally diverse crops can reduce the availability of resources that could otherwise be used by weeds. An experiment was conducted six times across the northeastern United States in 2013 and 2014 to examine the effects of functional diversity and species richness on weed suppr...

Improving tree establishment with forage crops

Treesearch

Eric J. Holzmueller; Carl W. Mize

2003-01-01

Tree establishment in Iowa can be difficult without adequate weed control. Although herbicides are effective at controlling weeds, they may not be desirable in riparian settings and some landowners are opposed to using them. An alternative to herbicides is the use of forage crops to control weeds. A research project was established in 1998 to evaluate the influence of...

Introduction to Weeds and Herbicides.

ERIC Educational Resources Information Center

Hartwig, Nathan L.

This agriculture extension service publication from Pennsylvania State University is an introduction to weed control and herbicide use. An initial discussion of the characteristics of weeds includes scientific naming, weed competition with crops, weed dispersal and dormancy, and conditions affecting weed seed germination. The main body of the…

Allelopathic cover crop prior to seeding is more important than subsequent grazing/mowing in grassland establishment

USGS Publications Warehouse

Milchunas, Daniel G.; Vandever, Mark W.; Ball, Leonard O.; Hyberg, Skip

2011-01-01

The effects of grazing, mowing, and type of cover crop were evaluated in a previous winter wheat–fallow cropland seeded to grassland under the Conservation Reserve Program in eastern Colorado. Prior to seeding, the fallow strips were planted to forage sorghum or wheat in alternating strips (cover crops), with no grazing, moderate to heavy grazing, and mowing (grazing treatments) superimposed 4 yr after planting and studied for 3 yr. Plots previously in wheat had more annual and exotic species than sorghum plots. Concomitantly, there were much greater abundances of perennial native grass and all native species in sorghum than wheat cropped areas. The competitive advantage gained by seeded species in sorghum plots resulted in large increases in rhizomatous western wheatgrass. Sorghum is known to be allelopathic and is used in crop agriculture rotations to suppress weeds and increase crop yields, consistent with the responses of weed and desired native species in this study. Grazing treatment had relatively minor effects on basal and canopy cover composition of annual or exotic species versus perennial native grass or native species. Although grazing treatment never was a significant main effect, it occasionally modified cover crop or year effects. Opportunistic grazing reduced exotic cheatgrass by year 3 but also decreased the native palatable western wheatgrass. Mowing was a less effective weed control practice than grazing. Vegetative basal cover and aboveground primary production varied primarily with year. Common management practices for revegetation/restoration currently use herbicides and mowing as weed control practices and restrict grazing in all stages of development. Results suggest that allelopathic cover crop selection and opportunistic grazing can be effective alternative grass establishment and weed control practices. Susceptibility, resistance, and interactions of weed and seeded species to allelopathic cover species/cultivars may be a fruitful area of research.

An early-killed rye cover crop has potential for weed management in edamame

USDA-ARS?s Scientific Manuscript database

The potential role of fall-seeded cover crops for weed management in edamame is unknown. Field experiments were conducted over three edamame growing seasons to test the following objectives: 1) determine the extent to which cover crop residue management systems influence edamame emergence while sele...

The risk of exotic and native plants as hosts for four pest thrips (Thysanoptera: Thripinae).

PubMed

Schellhorn, N A; Glatz, R V; Wood, G M

2010-10-01

Interactions among insect pests, crops and weeds are well recognised. In fact, the elimination of weed hosts outside of the crop is a common practice to control many insect-vectored viruses. However, little is known about interactions among insect pests, crops and native vegetation, and whether native plants may be used to revegetate areas where weed hosts have been eliminated as part of horticultural management regimes. We used the Northern Adelaide Plains horticultural region (South Australia, Australia) as a model system to study the potential of various plant taxa in hosting four pest thrips (three exotic, one native; Frankliniella occidentalis, F. schultzei, Thrips tabaci and T. imaginis) when located adjacent to, and distant from, horticultural crops. Flower funnels were used for standardised sampling of thrips on flowers from 19 exotic weed and 12 native plant species, representing 13 and three families, respectively. Flowers were sampled monthly over a year, and statistical analyses were performed to identify significant determinants of probability of thrips occurrence and density. Plant family was found to significantly influence both measures for each thrips species. In addition, crop proximity influenced the probability of occurrence for the two Frankliniella species (but only influenced density of the key pest F. occidentalis), and season influenced density of all four pest thrips. All native plant species tested had a low likelihood of hosting the three exotic thrips species. Overall, results suggest that judicious choice of surrounding vegetation has potential to be an important component of integrated pest management (IPM) while increasing biodiversity conservation.

Fungus-Farming Termites Selectively Bury Weedy Fungi that Smell Different from Crop Fungi.

PubMed

Katariya, Lakshya; Ramesh, Priya B; Gopalappa, Thejashwini; Desireddy, Sathish; Bessière, Jean-Marie; Borges, Renee M

2017-10-01

Mutualistic associations such as the fungal farms of insects are prone to parasitism and are consequently vulnerable to attack by weeds and pests. Therefore, efficient farm management requires quick detection of weeds for their elimination. Furthermore, if the available weedicides are non-specific, then the ability of insects to discriminate between crop and weeds becomes essential for targeted application of such compounds. Here, we demonstrate for the first time in fungus-farming insects, that worker castes of the fungus-growing termite Odontotermes obesus discriminate between their crop (Termitomyces) and the weedy (Pseudoxylaria) fungi, even if exposed to only fungal scents. Termites respond to the presence of fungal mycelium or scent alone, by burying the weed with the offered material such as soil or agar, possibly anointing the weed with chemicals in the process. The scent profiles of crop and weedy fungi are distinct and the differences are likely exploited by termites to selectively mount their defences. Sesquiterpene compounds such as aristolene and viridiflorol, which are absent from crop odours, may constitute the "weedy scent". Our results provide a general mechanism of how other fungus-farming insects could avoid indiscriminate application of non-specific fungicides which could lead to poisoning their crops, and have bearing on the stability of the mutualism between termites and their crop fungus in the face of parasitism by weedy fungi.

Benchmark study on glyphosate-resistant crop systems in the United States. Part 2: Perspectives.

PubMed

Owen, Micheal D K; Young, Bryan G; Shaw, David R; Wilson, Robert G; Jordan, David L; Dixon, Philip M; Weller, Stephen C

2011-07-01

A six-state, 5 year field project was initiated in 2006 to study weed management methods that foster the sustainability of genetically engineered (GE) glyphosate-resistant (GR) crop systems. The benchmark study field-scale experiments were initiated following a survey, conducted in the winter of 2005-2006, of farmer opinions on weed management practices and their views on GR weeds and management tactics. The main survey findings supported the premise that growers were generally less aware of the significance of evolved herbicide resistance and did not have a high recognition of the strong selection pressure from herbicides on the evolution of herbicide-resistant (HR) weeds. The results of the benchmark study survey indicated that there are educational challenges to implement sustainable GR-based crop systems and helped guide the development of the field-scale benchmark study. Paramount is the need to develop consistent and clearly articulated science-based management recommendations that enable farmers to reduce the potential for HR weeds. This paper provides background perspectives about the use of GR crops, the impact of these crops and an overview of different opinions about the use of GR crops on agriculture and society, as well as defining how the benchmark study will address these issues. Copyright © 2011 Society of Chemical Industry.

Seed deterioration in flooded agricultural fields during winter

USGS Publications Warehouse

Nelms, C.O.; Twedt, D.J.

1996-01-01

We determined rate of seed deterioration for 3 crops (corn, rice, and soybean) and 8 weeds commonly found in agricultural fields and moist-soil management units in the Mississippi Alluvial Valley (MAV). The weeds were broadleaf signalgrass (Brachiaria platyphylla), junglerice barnyardgrass (Echinochloa colonum), morningglory (Ipomoea sp.), panic grass (Panicum sp.), bull paspalum (Paspalum boscianum), red rice (Oryza sativa), hemp sesbania (Sesbania exaltata), and bristlegrass (Setaria sp.). Weed seeds, except morningglory, deteriorated slower than corn and soybean, whereas rice decomposed slower than all weed seeds except red rice and bull paspalum. For land managers desiring to provide plant food for wintering waterfowl, rice is clearly the most persistent small grain crop in the MAV. Persistence of weed seeds under flooded conditions throughout winter makes them a cost-effective alternative to traditional crops on land managed for waterfowl.

Simulating changes in cropping practises in conventional and glyphosate-tolerant maize. I. Effects on weeds.

PubMed

Colbach, Nathalie; Fernier, Alice; Le Corre, Valérie; Messéan, Antoine; Darmency, Henri

2017-04-01

Herbicide-tolerant (HT) crops such as those tolerant to glyphosate simplify weed management and make it more efficient, at least at short-term. Overreliance on the same herbicide though leads to the spread of resistant weeds. Here, the objective was to evaluate, with simulations, the impact on the advent of glyphosate resistance in weeds of modifications in agricultural practises resulting from introducing HT maize into cropping systems. First, we included a single-gene herbicide resistance submodel in the existing multispecific FLORSYS model. Then, we (1) simulated current conventional and probable HT cropping systems in two European regions, Aquitaine and Catalonia, (2) compared these systems in terms of glyphosate resistance, (3) identified pertinent cultural practises influencing glyphosate resistance, and (4) investigated correlations between cultural practises and species traits, using RLQ analyses. The simulation study showed that, during the analysed 28 years, (1) glyphosate spraying only results in glyphosate resistance in weeds when combined with other cultural factors favouring weed infestation, particularly no till; (2) pre-sowing glyphosate applications select more for herbicide resistance than post-sowing applications on HT crops; and (3) glyphosate spraying selects more for species traits avoiding exposure to the herbicide (e.g. delayed early growth, small leaf area) or compensating for fitness costs (e.g. high harvest index) than for actual resistance to glyphosate, (4) actual resistance is most frequent in species that do not avoid glyphosate, either via plant size or timing, and/or in less competitive species, (5) in case of efficient weed control measures, actual resistance proliferates best in outcrossing species. An advice table was built, with the quantitative, synthetic ranking of the crop management effects in terms of glyphosate-resistance management, identifying the optimal choices for each management technique.

The critical period of weed control in soybean (Glycine max (L.) Merr.) in north of Iran conditions.

PubMed

Keramati, Sara; Pirdashti, Hemmatollah; Esmaili, Mohammad Ali; Abbasian, Arastoo; Habibi, Marjaneh

2008-02-01

A field study was conducted in 2006 at Sari Agricultural and Natural Resources University, in order to determine the best time for weed control in soybean promising line, 033. Experiment was arranged in randomized complete block design with 4 replications and two series of treatments. In the first series, weeds were kept in place until crop reached V2 (second trifoliolate), V4 (fourth trifoliolate), V6 (sixth trifoliolate), R1 (beginning bloom, first flower), R3 (beginning pod), R5 (beginning seed) and were then removed and the crop kept weed-free for the rest of the season. In the second series, crops were kept weed-free until the above growth stages after which weeds were allowed to grow in the plots for the rest of the season. Whole season weedy and weed-free plots were included in the experiment for yield comparison. The results showed that among studied traits, grain yield, pod numbers per plant and weed biomass were affected significantly by control and interference treatments. The highest number of pods per plant was obtained from plots which kept weed-free for whole season control. Results showed that weed control should be carried out between V2 (26 day after planting) to R1 (63 day after planting) stages of soybean to provide maximum grain yield. Thus, it is possible to optimize the timing of weed control, which can serve to reduce the costs and side effects of intensive chemical weed control.

Managing weeds in potato rotations without herbicides

USDA-ARS?s Scientific Manuscript database

Managing weeds without herbicides requires an integration of methods and strategies and a change in how weeds are perceived. Weeds should be managed in a holistic, intentional and proactive manner. Successful weed management in organic systems attempts to understand the interactions between the crop...

Interactions between allelochemicals and the microbial community affect weed suppression following cover crop residue incorporation into soil

USDA-ARS?s Scientific Manuscript database

The objective of this study is to understand how soil microorganisms interact with cover crop-derived allelochemicals to suppress weed germination and growth following cover crop residue incorporation. We conducted a time series experiment by crossing sterilized and non-sterilized soil with four dif...

Winter weeds as inoculum sources of tomato spotted wilt virus and as reservoirs for its vector, Frankliniella fusca (Thysanoptera: Thripidae) in farmscapes of Georgia.

PubMed

Srinivasan, Rajagopalbabu; Riley, David; Diffie, Stan; Shrestha, Anita; Culbreath, Albert

2014-04-01

Thrips-transmitted Tomato spotted wilt virus (TSWV) has a broad host range including crops and weeds. In Georgia, TSWV is known to consistently affect peanut, tomato, pepper, and tobacco production. These crops are grown from March through November. In the crop-free period, weeds are presumed to serve as a green bridge for thrips and TSWV. Previous studies have identified several winter weeds as TSWV and thrips hosts. However, their ability to influence TSWV transmission in crops is still not completely understood. To further understand these interactions, population dynamics of two prevalent vectors, viz., Frankliniella fusca (Hinds) and Frankliniella occidentalis (Pergande), on selected winter weeds were monitored from October through April in four counties from 2004 to 2008. Peak populations were typically recorded in March. F. fusca and F. occidentalis adults were found on winter weeds and their percentages ranged from 0 to 68% in comparison with other adults. Immatures outnumbered all adults. Microcosm experiments indicated that the selected winter weeds differentially supported F. fusca reproduction and development. The time required to complete one generation (adult to adult) ranged from 11 to 16 d. Adult recovery ranged from 0.97 to 2.2 per female released. In addition, transmission assays revealed that thrips efficiently transmitted TSWV from peanut to weeds, the incidence of infection ranged from 10 to 55%. Back transmission assays with thrips from TSWV-infected weeds resulted in up to 75% TSWV infection in peanut. These whole-plant transmission and back transmission assays provide the basis for TSWV persistence in farmscapes year round.

Checklist for the crop weeds of Paraguay

PubMed Central

De Egea, Juana; Mereles, Fátima; Peña-Chocarro, María del Carmen; Céspedes, Gloria

2016-01-01

Abstract Paraguay, a country whose economy is based mainly on agriculture and livestock for export, has experienced a major expansion in mechanized crops during the last few decades. Despite being heavily dependent on agriculture, Paraguay has very limited research on crop weeds, in spite of these having a high economic impact on production. This work aims to update and enhance the knowledgebase on the most common weeds affecting productive fields throughout the different ecoregions of Paraguay. We present here the first checklist of crop weeds for the country, which includes a total of 256 taxa (189 species, 10 subspecies, 54 varieties and 3 forms), with the most species-rich families being Poaceae and Asteraceae followed by Malvaceae, Amaranthaceae, Fabaceae and Solanaceae. The list includes three new records for the country. Synonyms, distribution details within Paraguay, habit and a voucher specimen are provided for each taxon. PMID:27872557

Limited Fitness Advantages of Crop-Weed Hybrid Progeny Containing Insect-Resistant Transgenes (Bt/CpTI) in Transgenic Rice Field

PubMed Central

Yang, Xiao; Wang, Feng; Su, Jun; Lu, Bao-Rong

2012-01-01

Background The spread of insect-resistance transgenes from genetically engineered (GE) rice to its coexisting weedy rice (O. sativa f. spontanea) populations via gene flow creates a major concern for commercial GE rice cultivation. Transgene flow to weedy rice seems unavoidable. Therefore, characterization of potential fitness effect brought by the transgenes is essential to assess environmental consequences caused by crop-weed transgene flow. Methodology/Principal Findings Field performance of fitness-related traits was assessed in advanced hybrid progeny of F4 generation derived from a cross between an insect-resistant transgenic (Bt/CpTI) rice line and a weedy strain. The performance of transgene-positive hybrid progeny was compared with the transgene-negative progeny and weedy parent in pure and mixed planting of transgenic and nontransgenic plants under environmental conditions with natural vs. low insect pressure. Results showed that under natural insect pressure the insect-resistant transgenes could effectively suppress target insects and bring significantly increased fitness to transgenic plants in pure planting, compared with nontransgenic plants (including weedy parent). In contrast, no significant differences in fitness were detected under low insect pressure. However, such increase in fitness was not detected in the mixed planting of transgenic and nontransgenic plants due to significantly reduced insect pressure. Conclusions/Significance Insect-resistance transgenes may have limited fitness advantages to hybrid progeny resulted from crop-weed transgene flow owning to the significantly reduced ambient target insect pressure when an insect-resistant GE crop is grown. Given that the extensive cultivation of an insect-resistant GE crop will ultimately reduce the target insect pressure, the rapid spread of insect-resistance transgenes in weedy populations in commercial GE crop fields may be not likely to happen. PMID:22815975

High-residue cultivation timing impact on organic no-till soybean weed management

USDA-ARS?s Scientific Manuscript database

A cereal rye cover crop mulch can suppress summer annual weeds early in the soybean growing season. However, a multi-tactic weed management approach is required when annual weed seedbanks are large or perennial weeds are present. In such situations, the weed suppression from a cereal rye mulch can b...

Biology and management of two important Conyza weeds: a global review.

PubMed

Bajwa, Ali Ahsan; Sadia, Sehrish; Ali, Hafiz Haider; Jabran, Khawar; Peerzada, Arslan Masood; Chauhan, Bhagirath Singh

2016-12-01

Weed management is one of the prime concerns for sustainable crop production. Conyza bonariensis and Conyza canadensis are two of the most problematic, noxious, invasive and widespread weeds in modern-day agriculture. The biology, ecology and interference of C. bonariensis and C. canadensis have been reviewed here to highlight pragmatic management options. Both these species share a unique set of biological features, which enables them to invade and adapt a wide range of environmental conditions. Distinct reproductive biology and an efficient seed dispersal mechanism help these species to spread rapidly. Ability to interfere strongly and to host crop pests makes these two species worst weeds of cropping systems. These weed species cause 28-68 % yield loss in important field crops such as soybean and cotton every year. These weeds are more prevalent in no-till systems and, thus, becoming a major issue in conservation agriculture. Cultural practices such as crop rotations, seed rate manipulation, mulching, inter-row tillage and narrow row spacing may provide an effective control of these species. However, such methods are not feasible and applicable under all types of conditions. Different herbicides also provide a varying degree of control depending on crop, agronomic practices, herbicide dose, application time and season. However, both these species have evolved resistance against multiple herbicides, including glyphosate and paraquat. The use of alternative herbicides and integrated management strategies may provide better control of herbicide-resistant C. bonariensis and C. canadensis. Management plans based on the eco-biological interactions of these species may prove sustainable in the future.

Weed management practice and cropping sequence impact on soil residual nitrogen

USDA-ARS?s Scientific Manuscript database

Inefficient N uptake by crops from N fertilization and/or N mineralized from crop residue and soil organic matter results in the accumulation of soil residual N (NH4-N and NO3-N) which increases the potential for N leaching. The objective of this study was to evaluate the effects of weed management ...

Dryland pea production and water use in responses to tillage, crop rotation, and weed management practice

USDA-ARS?s Scientific Manuscript database

Pea has been used to replace fallow and sustain dryland crop yields in arid and semiarid regions, but information to optimize its management is required. We evaluated pea growth, yield, and water use in response to tillage, crop rotation, and weed management practice from 2005 to 2010 in the norther...

Weather-based pest forecasting for efficient crop protection

Treesearch

Rabiu Olatinwo; Gerrit Hoogenboom

2014-01-01

Although insects, pathogens, mites, nematodes, weeds, vertebrates, and arthropods are different in many ways, they are regarded as pests. They are a major constraint to crop productivity and profitability around the world caused by direct and indirect damage to valuable crops. Insect pests, pathogens, and weeds account for an estimated 45% of pre- and post-harvest...

Forage radish winter cover crop suppresses winter annual weeds in fall and before corn planting

USDA-ARS?s Scientific Manuscript database

Forage radish (Raphanus sativus L. var. longipinnatus) is a new winter cover crop in the Mid-Atlantic region. The objective of this project was to characterize the repeatability, amount, and duration of weed suppression during and after a fall-planted forage radish cover crop and to quantify the sub...

Weed control changes and genetically modified herbicide tolerant crops in the USA 1996–2012

PubMed Central

Brookes, Graham

2014-01-01

Crops that have been genetically modified (GM) to be tolerant to herbicides have been widely grown in the USA since 1996. The rapid and widespread adoption of this technology reflects the important economic and environmental benefits that farmers have derived from its use (equal to $21.7 billion additional farm income and a 225 million kg reduction in herbicide active ingredient use 1996–2012). During this time, weed control practices in these crops relative to the ‘conventional alternative’ have evolved to reflect experience of using the technology, the challenges that have arisen and the increasing focus in recent years on developing sustainable production systems. This paper examines the evidence on the changing nature of herbicides used with these crops and in particular how farmers addressed the challenge of weed resistance. The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods. It also facilitated many farmers being able to derive the economic and environmental benefits associated with switching from a plough-based to a no tillage or conservation tillage production system. In terms of herbicide use, the technology has also contributed to a change the profile of herbicides used. A broad range of, mostly selective herbicides has been replaced by one or 2 broad-spectrum herbicides (mostly glyphosate) used in conjunction with one or 2 other (complementary) herbicides. Since the mid-2000s, the average amount of herbicide applied and the associated environmental load, as measured by the EIQ indicator, have increased on both GM HT and conventional crops. A primary reason for these changes has been increasing incidence of weed species developing populations resistant to herbicides and increased awareness of the consequences of relying on a single or very limited number of herbicides for weed control. As a result, growers of GM HT crops have become much more proactive and diversified in their weed management programs in line with weed scientist recommendations and now include other herbicides (with different and complementary modes of action) in combination with glyphosate, even where instances of weed resistance to glyphosate have not been found. The willingness to proactively diversity weed management systems in the GM HT crops is also influenced by a desire to maintain effective weed control and hence continue to enjoy the benefits of no tillage and conservation tillage. Nevertheless, despite the increase in herbicide use in recent years, the use of GM HT technology continues to deliver significant economic and environmental gains to US farmers. PMID:25523177

Weed control changes and genetically modified herbicide tolerant crops in the USA 1996-2012.

PubMed

Brookes, Graham

2014-01-01

Crops that have been genetically modified (GM) to be tolerant to herbicides have been widely grown in the USA since 1996. The rapid and widespread adoption of this technology reflects the important economic and environmental benefits that farmers have derived from its use (equal to $21.7 billion additional farm income and a 225 million kg reduction in herbicide active ingredient use 1996-2012). During this time, weed control practices in these crops relative to the 'conventional alternative' have evolved to reflect experience of using the technology, the challenges that have arisen and the increasing focus in recent years on developing sustainable production systems. This paper examines the evidence on the changing nature of herbicides used with these crops and in particular how farmers addressed the challenge of weed resistance. The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods. It also facilitated many farmers being able to derive the economic and environmental benefits associated with switching from a plough-based to a no tillage or conservation tillage production system. In terms of herbicide use, the technology has also contributed to a change the profile of herbicides used. A broad range of, mostly selective herbicides has been replaced by one or 2 broad-spectrum herbicides (mostly glyphosate) used in conjunction with one or 2 other (complementary) herbicides. Since the mid-2000s, the average amount of herbicide applied and the associated environmental load, as measured by the EIQ indicator, have increased on both GM HT and conventional crops. A primary reason for these changes has been increasing incidence of weed species developing populations resistant to herbicides and increased awareness of the consequences of relying on a single or very limited number of herbicides for weed control. As a result, growers of GM HT crops have become much more proactive and diversified in their weed management programs in line with weed scientist recommendations and now include other herbicides (with different and complementary modes of action) in combination with glyphosate, even where instances of weed resistance to glyphosate have not been found. The willingness to proactively diversity weed management systems in the GM HT crops is also influenced by a desire to maintain effective weed control and hence continue to enjoy the benefits of no tillage and conservation tillage. Nevertheless, despite the increase in herbicide use in recent years, the use of GM HT technology continues to deliver significant economic and environmental gains to US farmers.

Selective fertilization with phosphite allows unhindered growth of cotton plants expressing the ptxD gene while suppressing weeds.

PubMed

Pandeya, Devendra; López-Arredondo, Damar L; Janga, Madhusudhana R; Campbell, LeAnne M; Estrella-Hernández, Priscila; Bagavathiannan, Muthukumar V; Herrera-Estrella, Luis; Rathore, Keerti S

2018-06-04

Weeds, which have been the bane of agriculture since the beginning of civilization, are managed manually, mechanically, and, more recently, by chemicals. However, chemical control options are rapidly shrinking due to the recent rise in the number of herbicide-resistant weeds in crop fields, with few alternatives on the horizon. Therefore, there is an urgent need for alternative weed suppression systems to sustain crop productivity while reducing our dependence on herbicides and tillage. Such a development will also allay some of the negative perceptions associated with the use of herbicide-resistance genes and heavy dependence on herbicides. Transgenic plants expressing the bacterial phosphite dehydrogenase ( ptxD ) gene gain an ability to convert phosphite (Phi) into orthophosphate [Pi, the metabolizable form of phosphorus (P)]. Such plants allow for a selective fertilization scheme, based on Phi as the sole source of P for the crop, while offering an effective alternative for suppressing weed growth. Here, we show that, when P is supplied in the form of Phi, ptxD -expressing cotton ( Gossypium hirsutum L.) plants outcompete, in both artificial substrates and natural soils from agricultural fields, three different monocot and dicot weed species intentionally introduced in the experiments, as well as weeds naturally present in the tested soils. Importantly, the ptxD /Phi system proved highly efficacious in inhibiting the growth of glyphosate-resistant Palmer amaranth. With over 250 weed species resistant to currently available herbicides, ptxD -transgenic plants fertilized with Phi could provide an effective alternative to suppressing the growth of these weeds while providing adequate nutrition to the crop. Copyright © 2018 the Author(s). Published by PNAS.

Loss of glyphosate efficacy: a changing weed spectrum in Georgia cotton

USDA-ARS?s Scientific Manuscript database

Introduction of glyphosate resistance into crops through genetic modification has revolutionized crop protection. Glyphosate, the proverbial silver bullet, is a broad spectrum herbicide with favorable environmental characteristics and effective broad-spectrum weed control that has greatly improved ...

Weed Mapping in Early-Season Maize Fields Using Object-Based Analysis of Unmanned Aerial Vehicle (UAV) Images

PubMed Central

Peña, José Manuel; Torres-Sánchez, Jorge; de Castro, Ana Isabel; Kelly, Maggi; López-Granados, Francisca

2013-01-01

The use of remote imagery captured by unmanned aerial vehicles (UAV) has tremendous potential for designing detailed site-specific weed control treatments in early post-emergence, which have not possible previously with conventional airborne or satellite images. A robust and entirely automatic object-based image analysis (OBIA) procedure was developed on a series of UAV images using a six-band multispectral camera (visible and near-infrared range) with the ultimate objective of generating a weed map in an experimental maize field in Spain. The OBIA procedure combines several contextual, hierarchical and object-based features and consists of three consecutive phases: 1) classification of crop rows by application of a dynamic and auto-adaptive classification approach, 2) discrimination of crops and weeds on the basis of their relative positions with reference to the crop rows, and 3) generation of a weed infestation map in a grid structure. The estimation of weed coverage from the image analysis yielded satisfactory results. The relationship of estimated versus observed weed densities had a coefficient of determination of r2=0.89 and a root mean square error of 0.02. A map of three categories of weed coverage was produced with 86% of overall accuracy. In the experimental field, the area free of weeds was 23%, and the area with low weed coverage (<5% weeds) was 47%, which indicated a high potential for reducing herbicide application or other weed operations. The OBIA procedure computes multiple data and statistics derived from the classification outputs, which permits calculation of herbicide requirements and estimation of the overall cost of weed management operations in advance. PMID:24146963

Weed mapping in early-season maize fields using object-based analysis of unmanned aerial vehicle (UAV) images.

PubMed

Peña, José Manuel; Torres-Sánchez, Jorge; de Castro, Ana Isabel; Kelly, Maggi; López-Granados, Francisca

2013-01-01

The use of remote imagery captured by unmanned aerial vehicles (UAV) has tremendous potential for designing detailed site-specific weed control treatments in early post-emergence, which have not possible previously with conventional airborne or satellite images. A robust and entirely automatic object-based image analysis (OBIA) procedure was developed on a series of UAV images using a six-band multispectral camera (visible and near-infrared range) with the ultimate objective of generating a weed map in an experimental maize field in Spain. The OBIA procedure combines several contextual, hierarchical and object-based features and consists of three consecutive phases: 1) classification of crop rows by application of a dynamic and auto-adaptive classification approach, 2) discrimination of crops and weeds on the basis of their relative positions with reference to the crop rows, and 3) generation of a weed infestation map in a grid structure. The estimation of weed coverage from the image analysis yielded satisfactory results. The relationship of estimated versus observed weed densities had a coefficient of determination of r(2)=0.89 and a root mean square error of 0.02. A map of three categories of weed coverage was produced with 86% of overall accuracy. In the experimental field, the area free of weeds was 23%, and the area with low weed coverage (<5% weeds) was 47%, which indicated a high potential for reducing herbicide application or other weed operations. The OBIA procedure computes multiple data and statistics derived from the classification outputs, which permits calculation of herbicide requirements and estimation of the overall cost of weed management operations in advance.

Development and Evaluation of a Combined Cultivator and Band Sprayer with a Row-Centering RTK-GPS Guidance System

PubMed Central

Perez-Ruiz, Manuel; Carballido, Jacob; Agüera, Juan; Rodríguez-Lizana, Antonio

2013-01-01

Typically, low-pressure sprayers are used to uniformly apply pre- and post-emergent herbicides to control weeds in crop rows. An innovative machine for weed control in inter-row and intra-row areas, with a unique combination of inter-row cultivation tooling and intra-row band spraying for six rows and an electro-hydraulic side-shift frame controlled by a GPS system, was developed and evaluated. Two weed management strategies were tested in the field trials: broadcast spraying (the conventional method) and band spraying with mechanical weed control using RTK-GPS (the experimental method). This approach enabled the comparison between treatments from the perspective of cost savings and efficacy in weed control for a sugar beet crop. During the 2010–2011 season, the herbicide application rate (112 L ha−1) of the experimental method was approximately 50% of the conventional method, and thus a significant reduction in the operating costs of weed management was achieved. A comparison of the 0.2-trimmed means of weed population post-treatment showed that the treatments achieved similar weed control rates at each weed survey date. Sugar beet yields were similar with both methods (p = 0.92). The use of the experimental equipment is cost-effective on ≥20 ha of crops. These initial results show good potential for reducing herbicide application in the Spanish beet industry. PMID:23478600

Development and evaluation of a combined cultivator and band sprayer with a row-centering RTK-GPS guidance system.

PubMed

Perez-Ruiz, Manuel; Carballido, Jacob; Agüera, Juan; Rodríguez-Lizana, Antonio

2013-03-11

Typically, low-pressure sprayers are used to uniformly apply pre- and post-emergent herbicides to control weeds in crop rows. An innovative machine for weed control in inter-row and intra-row areas, with a unique combination of inter-row cultivation tooling and intra-row band spraying for six rows and an electro-hydraulic side-shift frame controlled by a GPS system, was developed and evaluated. Two weed management strategies were tested in the field trials: broadcast spraying (the conventional method) and band spraying with mechanical weed control using RTK-GPS (the experimental method). This approach enabled the comparison between treatments from the perspective of cost savings and efficacy in weed control for a sugar beet crop. During the 2010-2011 season, the herbicide application rate (112 L ha(-1)) of the experimental method was approximately 50% of the conventional method, and thus a significant reduction in the operating costs of weed management was achieved. A comparison of the 0.2-trimmed means of weed population post-treatment showed that the treatments achieved similar weed control rates at each weed survey date. Sugar beet yields were similar with both methods (p = 0.92). The use of the experimental equipment is cost-effective on ≥20 ha of crops. These initial results show good potential for reducing herbicide application in the Spanish beet industry.

Soil coverage evolution and wind erosion risk on summer crops under contrasting tillage systems

NASA Astrophysics Data System (ADS)

Mendez, Mariano J.; Buschiazzo, Daniel E.

2015-03-01

The effectiveness of wind erosion control by soil surface conditions and crop and weed canopy has been well studied in wind tunnel experiments. The aim of this study is to assess the combined effects of these variables under field conditions. Soil surface conditions, crop and weed coverage, plant residue, and non-erodible aggregates (NEA) were measured in the field between the fallow start and the growth period of sunflower (Helianthus annuus) and corn (Zea mays). Both crops were planted on a sandy-loam Entic Haplustoll with conventional-(CT), vertical-(VT) and no-till (NT) tillage systems. Wind erosion was estimated by means of the spreadsheet version the Revised Wind Erosion Equation and the soil coverage was measured each 15 days. Results indicated that wind erosion was mostly negligible in NT, exceeding the tolerable levels (estimated between 300 and 1400 kg ha-1 year-1 by Verheijen et al. (2009)) only in an year with high climatic erosivity. Wind erosion exceeded the tolerable levels in most cases in CT and VT, reaching values of 17,400 kg ha-1. Wind erosion was 2-10 times higher after planting of both crops than during fallows. During the fallows, the soil was mostly well covered with plant residues and NEA in CT and VT and with residues and weeds in NT. High wind erosion amounts occurring 30 days after planting in all tillage systems were produced by the destruction of coarse aggregates and the burying of plant residues during planting operations and rains. Differences in soil protection after planting were given by residues of previous crops and growing weeds. The growth of weeds 2-4 weeks after crop planting contributed to reduce wind erosion without impacting in crops yields. An accurate weeds management in semiarid lands can contribute significantly to control wind erosion. More field studies are needed in order to develop management strategies to reduce wind erosion.

Allelopathic cover crop prior to seeding is more important than subsequent grazing/mowing in Grassland establishment

USGS Publications Warehouse

Milchunas, D.G.; Vandever, M.W.; Ball, L.O.; Hyberg, S.

2011-01-01

The effects of grazing, mowing, and type of cover crop were evaluated in a previous winter wheat-fallow cropland seeded to grassland under the Conservation Reserve Program in eastern Colorado. Prior to seeding, the fallow strips were planted to forage sorghum or wheat in alternating strips (cover crops), with no grazing, moderate to heavy grazing, and mowing (grazing treatments) superimposed 4 yr after planting and studied for 3 yr. Plots previously in wheat had more annual and exotic species than sorghum plots. Concomitantly, there were much greater abundances of perennial native grass and all native species in sorghum than wheat cropped areas. The competitive advantage gained by seeded species in sorghum plots resulted in large increases in rhizomatous western wheatgrass. Sorghum is known to be allelopathic and is used in crop agriculture rotations to suppress weeds and increase crop yields, consistent with the responses of weed and desired native species in this study. Grazing treatment had relatively minor effects on basal and canopy cover composition of annual or exotic species versus perennial native grass or native species. Although grazing treatment never was a significant main effect, it occasionally modified cover crop or year effects. Opportunistic grazing reduced exotic cheatgrass by year 3 but also decreased the native palatable western wheatgrass. Mowing was a less effective weed control practice than grazing. Vegetative basal cover and aboveground primary production varied primarily with year. Common management practices for revegetation/restoration currently use herbicides and mowing as weed control practices and restrict grazing in all stages of development. Results suggest that allelopathic cover crop selection and opportunistic grazing can be effective alternative grass establishment and weed control practices. Susceptibility, resistance, and interactions of weed and seeded species to allelopathic cover species/cultivars may be a fruitful area of research. ?? 2011 Society for Range Management.

Herbicide resistance and biodiversity: agronomic and environmental aspects of genetically modified herbicide-resistant plants.

PubMed

Schütte, Gesine; Eckerstorfer, Michael; Rastelli, Valentina; Reichenbecher, Wolfram; Restrepo-Vassalli, Sara; Ruohonen-Lehto, Marja; Saucy, Anne-Gabrielle Wuest; Mertens, Martha

2017-01-01

Farmland biodiversity is an important characteristic when assessing sustainability of agricultural practices and is of major international concern. Scientific data indicate that agricultural intensification and pesticide use are among the main drivers of biodiversity loss. The analysed data and experiences do not support statements that herbicide-resistant crops provide consistently better yields than conventional crops or reduce herbicide amounts. They rather show that the adoption of herbicide-resistant crops impacts agronomy, agricultural practice, and weed management and contributes to biodiversity loss in several ways: (i) many studies show that glyphosate-based herbicides, which were commonly regarded as less harmful, are toxic to a range of aquatic organisms and adversely affect the soil and intestinal microflora and plant disease resistance; the increased use of 2,4-D or dicamba, linked to new herbicide-resistant crops, causes special concerns. (ii) The adoption of herbicide-resistant crops has reduced crop rotation and favoured weed management that is solely based on the use of herbicides. (iii) Continuous herbicide resistance cropping and the intensive use of glyphosate over the last 20 years have led to the appearance of at least 34 glyphosate-resistant weed species worldwide. Although recommended for many years, farmers did not counter resistance development in weeds by integrated weed management, but continued to rely on herbicides as sole measure. Despite occurrence of widespread resistance in weeds to other herbicides, industry rather develops transgenic crops with additional herbicide resistance genes. (iv) Agricultural management based on broad-spectrum herbicides as in herbicide-resistant crops further decreases diversity and abundance of wild plants and impacts arthropod fauna and other farmland animals. Taken together, adverse impacts of herbicide-resistant crops on biodiversity, when widely adopted, should be expected and are indeed very hard to avoid. For that reason, and in order to comply with international agreements to protect and enhance biodiversity, agriculture needs to focus on practices that are more environmentally friendly, including an overall reduction in pesticide use. (Pesticides are used for agricultural as well non-agricultural purposes. Most commonly they are used as plant protection products and regarded as a synonym for it and so also in this text.).

An Approach to the Use of Depth Cameras for Weed Volume Estimation

PubMed Central

Andújar, Dionisio; Dorado, José; Fernández-Quintanilla, César; Ribeiro, Angela

2016-01-01

The use of depth cameras in precision agriculture is increasing day by day. This type of sensor has been used for the plant structure characterization of several crops. However, the discrimination of small plants, such as weeds, is still a challenge within agricultural fields. Improvements in the new Microsoft Kinect v2 sensor can capture the details of plants. The use of a dual methodology using height selection and RGB (Red, Green, Blue) segmentation can separate crops, weeds, and soil. This paper explores the possibilities of this sensor by using Kinect Fusion algorithms to reconstruct 3D point clouds of weed-infested maize crops under real field conditions. The processed models showed good consistency among the 3D depth images and soil measurements obtained from the actual structural parameters. Maize plants were identified in the samples by height selection of the connected faces and showed a correlation of 0.77 with maize biomass. The lower height of the weeds made RGB recognition necessary to separate them from the soil microrelief of the samples, achieving a good correlation of 0.83 with weed biomass. In addition, weed density showed good correlation with volumetric measurements. The canonical discriminant analysis showed promising results for classification into monocots and dictos. These results suggest that estimating volume using the Kinect methodology can be a highly accurate method for crop status determination and weed detection. It offers several possibilities for the automation of agricultural processes by the construction of a new system integrating these sensors and the development of algorithms to properly process the information provided by them. PMID:27347972

An Approach to the Use of Depth Cameras for Weed Volume Estimation.

PubMed

Andújar, Dionisio; Dorado, José; Fernández-Quintanilla, César; Ribeiro, Angela

2016-06-25

The use of depth cameras in precision agriculture is increasing day by day. This type of sensor has been used for the plant structure characterization of several crops. However, the discrimination of small plants, such as weeds, is still a challenge within agricultural fields. Improvements in the new Microsoft Kinect v2 sensor can capture the details of plants. The use of a dual methodology using height selection and RGB (Red, Green, Blue) segmentation can separate crops, weeds, and soil. This paper explores the possibilities of this sensor by using Kinect Fusion algorithms to reconstruct 3D point clouds of weed-infested maize crops under real field conditions. The processed models showed good consistency among the 3D depth images and soil measurements obtained from the actual structural parameters. Maize plants were identified in the samples by height selection of the connected faces and showed a correlation of 0.77 with maize biomass. The lower height of the weeds made RGB recognition necessary to separate them from the soil microrelief of the samples, achieving a good correlation of 0.83 with weed biomass. In addition, weed density showed good correlation with volumetric measurements. The canonical discriminant analysis showed promising results for classification into monocots and dictos. These results suggest that estimating volume using the Kinect methodology can be a highly accurate method for crop status determination and weed detection. It offers several possibilities for the automation of agricultural processes by the construction of a new system integrating these sensors and the development of algorithms to properly process the information provided by them.

Agronomic Weeds.

ERIC Educational Resources Information Center

Hartwig, Nathan L.

This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact…

Benchmark study on glyphosate-resistant cropping systems in the United States. Part 6: Timeliness of economic decision-making in implementing weed resistance management strategies.

PubMed

Weirich, Jason W; Shaw, David R; Coble, Keith H; Owen, Micheal D K; Dixon, Philip M; Weller, Stephen C; Young, Bryan G; Wilson, Robert G; Jordan, David L

2011-07-01

The introduction of glyphosate-resistant (GR) crops in the late 1990s made weed control in maize, cotton and soybean simple. With the rapid adoption of GR crops, many growers began to rely solely on glyphosate for weed control. This eventually led to the evolution of GR weeds. Growers are often reluctant to adopt a weed resistance best management practice (BMP) because of the added cost of additional herbicides to weed control programs which would reduce short-term revenue. This study was designed to evaluate when a grower that is risk neutral (profit maximizing) or risk averse should adopt a weed resistance BMP. Whether a grower is risk neutral or risk averse, the optimal decision would be to adopt a weed resistance BMP when the expected loss in revenue is greater than 30% and the probability of resistance evolution is 0.1 or greater. However, if the probability of developing resistance increases to 0.3, then the best decision would be to adopt a weed resistance BMP when the expected loss is 10% or greater. Given the scenarios analyzed, risk-neutral or risk-averse growers should implement a weed resistance BMP with confidence that they have made the right decision economically and avoided the risk of lost revenue from resistance. If the grower wants to continue to see the same level of return, adoption of BMP is required. Copyright © 2011 Society of Chemical Industry.

Effect of tillage system on yield and weed populations of soybean ( Glycin Max L.).

PubMed

Hosseini, Seyed Z; Firouzi, Saeed; Aminpanah, Hashem; Sadeghnejhad, Hamid R

2016-03-01

Field experiment was conducted at Agricultural and Natural Resources Research Center of Golestan Province, Iran, to determine the effects of tillage system and weed management regime on yield and weed populations in soybean ( Glycin max L.). The experimental design was a split plot where the whole plot portion was a randomized complete block with three replicates. Main plots were tillage system: 1- No-till row crop seeding, 2- No-till seed drilling, 3- Tillage with disc harrow and drill planting, 4- Tillage with chisel packer and drill planting. The subplots were weed management regimes: 1-Weed control with herbicide application, 2- Hand weeding, 3- Herbicide application plus hand weeding, and 4- Non-weeding. Results indicated that the main effects of tillage system and weed management regime were significant for seed yield, pod number per plant, seed number per pod, weed density and biomass, while their interaction were significant only for weed density, weed biomass, and seed number per pod. The highest grain yields (3838 kg ha-1) were recorded for No-till row crop seeding. The highest seed yield (3877 kg ha-1) also was recorded for weed control with herbicide and hand weeding treatment, followed by hand weeding (3379 kg ha-1).

Integrated weed management strategies in cover crop-based, organic rotational no-till corn and soybean in the mid-Atlantic region

USDA-ARS?s Scientific Manuscript database

Cover crop-based, organic rotational no-till (CCORNT) corn and soybean systems have been developed in the mid-Atlantic region to build soil health, increase management flexibility, and reduce labor. In this system, a roll-crimped cover crop mulch provides within-season weed suppression in no-till co...

Real-Time Blob-Wise Sugar Beets VS Weeds Classification for Monitoring Fields Using Convolutional Neural Networks

NASA Astrophysics Data System (ADS)

Milioto, A.; Lottes, P.; Stachniss, C.

2017-08-01

UAVs are becoming an important tool for field monitoring and precision farming. A prerequisite for observing and analyzing fields is the ability to identify crops and weeds from image data. In this paper, we address the problem of detecting the sugar beet plants and weeds in the field based solely on image data. We propose a system that combines vegetation detection and deep learning to obtain a high-quality classification of the vegetation in the field into value crops and weeds. We implemented and thoroughly evaluated our system on image data collected from different sugar beet fields and illustrate that our approach allows for accurately identifying the weeds on the field.

Composition and diversity of weed communities in Al-Jouf province, northern Saudi Arabia

PubMed Central

Gomaa, Nasr H.

2012-01-01

The aim of this study was to identify the main weed communities in Al-Jouf province in northern Saudi Arabia. Moreover, the composition and diversity of these communities were studied in relation to soil variables and crop type. Some 54 stands representing olive orchards, date palm orchards, wheat crop and watermelon crop were studied, using ten quadrats (1 × 1 m) per stand. A total of 71 species belonging to 22 families and 61 genera were observed. The classification of vegetation using the Two Way Indicator Species Analysis (TWINSPAN) resulted in the recognition of four vegetation groups representing wheat crop, orchards in winter season, orchards in summer season and watermelon crop. These results suggested the importance of both crop and season for the formation of weed community. Detrended Correspondence Analysis (DCA) showed that these groups are clearly distinguished by the first two DCA axes. The species richness was higher in both olive and date palm orchards than in wheat and watermelon crops. This pattern of species richness could be related to farm management practices and habitat micro-heterogeneity. Soil electrical conductivity, organic carbon and soil texture showed significant correlations with species richness and the cover values of some dominant species, suggesting the significant role of soil characteristics in weed community structure and diversity. PMID:23961198

Allele Distributions at Hybrid Incompatibility Loci Facilitate the Potential for Gene Flow between Cultivated and Weedy Rice in the US

PubMed Central

Craig, Stephanie M.; Reagon, Michael; Resnick, Lauren E.; Caicedo, Ana L.

2014-01-01

The accumulation of independent mutations over time in two populations often leads to reproductive isolation. Reproductive isolation between diverging populations may be reinforced by barriers that occur either pre- or postzygotically. Hybrid sterility is the most common form of postzygotic isolation in plants. Four postzygotic sterility loci, comprising three hybrid sterility systems (Sa, s5, DPL), have been recently identified in Oryza sativa. These loci explain, in part, the limited hybridization that occurs between the domesticated cultivated rice varieties, O. sativa spp. japonica and O. sativa spp. indica. In the United States, cultivated fields of japonica rice are often invaded by conspecific weeds that have been shown to be of indica origin. Crop-weed hybrids have been identified in crop fields, but at low frequencies. Here we examined the possible role of these hybrid incompatibility loci in the interaction between cultivated and weedy rice. We identified a novel allele at Sa that seemingly prevents loss of fertility in hybrids. Additionally, we found wide-compatibility type alleles at strikingly high frequencies at the Sa and s5 loci in weed groups, and a general lack of incompatible alleles between crops and weeds at the DPL loci. Our results suggest that weedy individuals, particularly those of the SH and BRH groups, should be able to freely hybridize with the local japonica crop, and that prezygotic factors, such as differences in flowering time, have been more important in limiting weed-crop gene flow in the past. As the selective landscape for weedy rice changes due to increased use of herbicide resistant strains of cultivated rice, the genetic barriers that hinder indica-japonica hybridization cannot be counted on to limit the flow of favorable crop genes into weeds. PMID:24489758

Evolutionary Agroecology: the potential for cooperative, high density, weed-suppressing cereals.

PubMed

Weiner, Jacob; Andersen, Sven B; Wille, Wibke K-M; Griepentrog, Hans W; Olsen, Jannie M

2010-09-01

Evolutionary theory can be applied to improve agricultural yields and/or sustainability, an approach we call Evolutionary Agroecology. The basic idea is that plant breeding is unlikely to improve attributes already favored by millions of years of natural selection, whereas there may be unutilized potential in selecting for attributes that increase total crop yield but reduce plants' individual fitness. In other words, plant breeding should be based on group selection. We explore this approach in relation to crop-weed competition, and argue that it should be possible to develop high density cereals that can utilize their initial size advantage over weeds to suppress them much better than under current practices, thus reducing or eliminating the need for chemical or mechanical weed control. We emphasize the role of density in applying group selection to crops: it is competition among individuals that generates the 'Tragedy of the Commons', providing opportunities to improve plant production by selecting for attributes that natural selection would not favor. When there is competition for light, natural selection of individuals favors a defensive strategy of 'shade avoidance', but a collective, offensive 'shading' strategy could increase weed suppression and yield in the high density, high uniformity cropping systems we envision.

Weed Community Response to No-Till in North America

USDA-ARS?s Scientific Manuscript database

Scientists and producers in Ukraine are interested in no-till crop production, but are concerned about weed management. In North America, producers have used no-till systems for several decades without increasing weed community density in croplands. Initially, weed density escalated with no-till, ...

Tolerance of chickpeas (Cicer arietinum) to postemergence applied broadleaf herbicides

USDA-ARS?s Scientific Manuscript database

Chickpea producers currently have no postemergence (POST) applied herbicides labeled for broadleaf weed control and rely heavily on preemergence (PRE) herbicides to manage weeds. Severe crop losses from broadleaf weed competition and harvest losses from weeds impeding harvest can occur when PRE herb...

Comparisons of weed community, soil health and economic performance between wheat-maize and garlic-soybean rotation systems under different weed managements

PubMed Central

Muminov, Mahmud A.; Guo, Liyue; Song, Yanjie; Gu, Xian; Cen, Yu; Meng, Jie

2018-01-01

This study compared the impacts of different weed managements on weed community, soil health and economic performance between the wheat–maize (WM) and garlic–soybean (GS) rotations. A total of four treatments (H0T, tillage without herbicide; H0T0, without both herbicide and tillage; HT, both herbicide and tillage; HT0, herbicide without tillage) were designed for both rotations. A total of 16 weed species were recorded in the WM rotation, with life forms of 62% for annuals, 12% for annual + perennial and 20% for perennials. While in the GS rotation, there were 17 weed species, with 71% being annuals. When crop rotation changed from WM to GS, the topsoil layer seed bank (0–5 cm) decreased by 137%. GS rotation always had higher earthworm densities than that of WM under the same condition. Organic weed control (H0T, H0T0) from both WM and GS added more soil organic matters than the chemical methods (HT and HT0). Economically, up to 69% higher net profit had been achieved in the GS than WM for their organic products. This study provides an ecological basis to guide organic farming practices, especially for weed management in the future. PMID:29868258

Crop/weed discrimination using near-infrared reflectance spectroscopy (NIRS)

NASA Astrophysics Data System (ADS)

Zhang, Yun; He, Yong

2006-09-01

The traditional uniform herbicide application often results in an over chemical residues on soil, crop plants and agriculture produce, which have imperiled the environment and food security. Near-infrared reflectance spectroscopy (NIRS) offers a promising means for weed detection and site-specific herbicide application. In laboratory, a total of 90 samples (30 for each species) of the detached leaves of two weeds, i.e., threeseeded mercury (Acalypha australis L.) and fourleafed duckweed (Marsilea quadrfolia L.), and one crop soybean (Glycine max) was investigated for NIRS on 325- 1075 nm using a field spectroradiometer. 20 absorbance samples of each species after pretreatment were exported and the lacked Y variables were assigned independent values for partial least squares (PLS) analysis. During the combined principle component analysis (PCA) on 400-1000 nm, the PC1 and PC2 could together explain over 91% of the total variance and detect the three plant species with 98.3% accuracy. The full-cross validation results of PLS, i.e., standard error of prediction (SEP) 0.247, correlation coefficient (r) 0.954 and root mean square error of prediction (RMSEP) 0.245, indicated an optimum model for weed identification. By predicting the remaining 10 samples of each species in the PLS model, the results with deviation presented a 100% crop/weed detection rate. Thus, it could be concluded that PLS was an available alternative of for qualitative weed discrimination on NTRS.

Crop characteristics and weed Interactions of diverse Rrecurrent Inbred Lines (RILs) from a weed-suppressive x non-suppressive rice mapping population

USDA-ARS?s Scientific Manuscript database

ndica rice genotypes with enhanced weed suppression traits have been previously identified as potentially useful in supplementing weed control efforts in drill-seeded systems in the southern USA. A particularly weed-suppressive indica genotype (PI 312777) that was also high tillering and high yield...

Response of Pennsylvania native plant species to dicamba and/or glyphosate

EPA Science Inventory

Weeds may become resistant to intensive and extensive use of specific herbicides associated with the growth of herbicide tolerant crops, e.g., the use of glyphosate for weed control with glyphosate tolerant soybeans. To counter this resistance, crops modified to contain genes for...

Herbicide-Resistance in Crops and Weeds: A Historical and Current Perspective

USDA-ARS?s Scientific Manuscript database

Herbicides are the principal economic means of weed management on >90% of U.S. farmland. Herbicide-resistant crop cultivars have been used widely since 1995. Pest disciplines and other life sciences have various definitions of resistance that share commonalities. Development of herbicide resistant w...

AXXE® (pelargonic acid) and Racer® (ammonium nonanoate): Weed control comparisons

USDA-ARS?s Scientific Manuscript database

Organic vegetable producers need herbicides that can provide effective season-long weed control. The availability and use of effective post-emergence organic herbicides would increase the likelihood of season-long weed control, reduce crop loses, and decrease the introduction of additional weed seed...

Sweat, Brain-Power, Horsepower, and Time - The Keys to Controlling Weeds

USDA-ARS?s Scientific Manuscript database

Weed control in organic crop production is difficult and costly. Early studies on organic weed control in conservation tillage systems were disappointing. Research shifted to organic weed control in conventional tillage systems. Intense cultivation with a tine weeder was the most consistent metho...

Organic crop production's top research priority: Pestiphytology

USDA-ARS?s Scientific Manuscript database

Pestiphytology is the study of pest plants, commonly referred to as weeds. In a recent national survey, weed research was designated as the top research priority by organic producers. Manual weed control is a costly practice that can quickly decrease return on investment, while the absence of weed...

Dynamics of Weeds in the Soil Seed Bank: A Hidden Markov Model to Estimate Life History Traits from Standing Plant Time Series.

PubMed

Borgy, Benjamin; Reboud, Xavier; Peyrard, Nathalie; Sabbadin, Régis; Gaba, Sabrina

2015-01-01

Predicting the population dynamics of annual plants is a challenge due to their hidden seed banks in the field. However, such predictions are highly valuable for determining management strategies, specifically in agricultural landscapes. In agroecosystems, most weed seeds survive during unfavourable seasons and persist for several years in the seed bank. This causes difficulties in making accurate predictions of weed population dynamics and life history traits (LHT). Consequently, it is very difficult to identify management strategies that limit both weed populations and species diversity. In this article, we present a method of assessing weed population dynamics from both standing plant time series data and an unknown seed bank. We use a Hidden Markov Model (HMM) to obtain estimates of over 3,080 botanical records for three major LHT: seed survival in the soil, plant establishment (including post-emergence mortality), and seed production of 18 common weed species. Maximum likelihood and Bayesian approaches were complementarily used to estimate LHT values. The results showed that the LHT provided by the HMM enabled fairly accurate estimates of weed populations in different crops. There was a positive correlation between estimated germination rates and an index of the specialisation to the crop type (IndVal). The relationships between estimated LHTs and that between the estimated LHTs and the ecological characteristics of weeds provided insights into weed strategies. For example, a common strategy to cope with agricultural practices in several weeds was to produce less seeds and increase germination rates. This knowledge, especially of LHT for each type of crop, should provide valuable information for developing sustainable weed management strategies.

Dynamics of Weeds in the Soil Seed Bank: A Hidden Markov Model to Estimate Life History Traits from Standing Plant Time Series

PubMed Central

Borgy, Benjamin; Reboud, Xavier; Peyrard, Nathalie; Sabbadin, Régis; Gaba, Sabrina

2015-01-01

Predicting the population dynamics of annual plants is a challenge due to their hidden seed banks in the field. However, such predictions are highly valuable for determining management strategies, specifically in agricultural landscapes. In agroecosystems, most weed seeds survive during unfavourable seasons and persist for several years in the seed bank. This causes difficulties in making accurate predictions of weed population dynamics and life history traits (LHT). Consequently, it is very difficult to identify management strategies that limit both weed populations and species diversity. In this article, we present a method of assessing weed population dynamics from both standing plant time series data and an unknown seed bank. We use a Hidden Markov Model (HMM) to obtain estimates of over 3,080 botanical records for three major LHT: seed survival in the soil, plant establishment (including post-emergence mortality), and seed production of 18 common weed species. Maximum likelihood and Bayesian approaches were complementarily used to estimate LHT values. The results showed that the LHT provided by the HMM enabled fairly accurate estimates of weed populations in different crops. There was a positive correlation between estimated germination rates and an index of the specialisation to the crop type (IndVal). The relationships between estimated LHTs and that between the estimated LHTs and the ecological characteristics of weeds provided insights into weed strategies. For example, a common strategy to cope with agricultural practices in several weeds was to produce less seeds and increase germination rates. This knowledge, especially of LHT for each type of crop, should provide valuable information for developing sustainable weed management strategies. PMID:26427023

A True-Color Sensor and Suitable Evaluation Algorithm for Plant Recognition

PubMed Central

Schmittmann, Oliver; Schulze Lammers, Peter

2017-01-01

Plant-specific herbicide application requires sensor systems for plant recognition and differentiation. A literature review reveals a lack of sensor systems capable of recognizing small weeds in early stages of development (in the two- or four-leaf stage) and crop plants, of making spraying decisions in real time and, in addition, are that are inexpensive and ready for practical use in sprayers. The system described in this work is based on free cascadable and programmable true-color sensors for real-time recognition and identification of individual weed and crop plants. The application of this type of sensor is suitable for municipal areas and farmland with and without crops to perform the site-specific application of herbicides. Initially, databases with reflection properties of plants, natural and artificial backgrounds were created. Crop and weed plants should be recognized by the use of mathematical algorithms and decision models based on these data. They include the characteristic color spectrum, as well as the reflectance characteristics of unvegetated areas and areas with organic material. The CIE-Lab color-space was chosen for color matching because it contains information not only about coloration (a- and b-channel), but also about luminance (L-channel), thus increasing accuracy. Four different decision making algorithms based on different parameters are explained: (i) color similarity (ΔE); (ii) color similarity split in ΔL, Δa and Δb; (iii) a virtual channel ‘d’ and (iv) statistical distribution of the differences of reflection backgrounds and plants. Afterwards, the detection success of the recognition system is described. Furthermore, the minimum weed/plant coverage of the measuring spot was calculated by a mathematical model. Plants with a size of 1–5% of the spot can be recognized, and weeds in the two-leaf stage can be identified with a measuring spot size of 5 cm. By choosing a decision model previously, the detection quality can be increased. Depending on the characteristics of the background, different models are suitable. Finally, the results of field trials on municipal areas (with models of plants), winter wheat fields (with artificial plants) and grassland (with dock) are shown. In each experimental variant, objects and weeds could be recognized. PMID:28786922

A True-Color Sensor and Suitable Evaluation Algorithm for Plant Recognition.

PubMed

Schmittmann, Oliver; Schulze Lammers, Peter

2017-08-08

Plant-specific herbicide application requires sensor systems for plant recognition and differentiation. A literature review reveals a lack of sensor systems capable of recognizing small weeds in early stages of development (in the two- or four-leaf stage) and crop plants, of making spraying decisions in real time and, in addition, are that are inexpensive and ready for practical use in sprayers. The system described in this work is based on free cascadable and programmable true-color sensors for real-time recognition and identification of individual weed and crop plants. The application of this type of sensor is suitable for municipal areas and farmland with and without crops to perform the site-specific application of herbicides. Initially, databases with reflection properties of plants, natural and artificial backgrounds were created. Crop and weed plants should be recognized by the use of mathematical algorithms and decision models based on these data. They include the characteristic color spectrum, as well as the reflectance characteristics of unvegetated areas and areas with organic material. The CIE-Lab color-space was chosen for color matching because it contains information not only about coloration (a- and b-channel), but also about luminance (L-channel), thus increasing accuracy. Four different decision making algorithms based on different parameters are explained: (i) color similarity (ΔE); (ii) color similarity split in ΔL, Δa and Δb; (iii) a virtual channel 'd' and (iv) statistical distribution of the differences of reflection backgrounds and plants. Afterwards, the detection success of the recognition system is described. Furthermore, the minimum weed/plant coverage of the measuring spot was calculated by a mathematical model. Plants with a size of 1-5% of the spot can be recognized, and weeds in the two-leaf stage can be identified with a measuring spot size of 5 cm. By choosing a decision model previously, the detection quality can be increased. Depending on the characteristics of the background, different models are suitable. Finally, the results of field trials on municipal areas (with models of plants), winter wheat fields (with artificial plants) and grassland (with dock) are shown. In each experimental variant, objects and weeds could be recognized.

Fruit Crop Pests. MEP 312.

ERIC Educational Resources Information Center

Weaver, Leslie O.; And Others

As part of a cooperative extension service series by the University of Maryland this publication introduces the identification and control of common agricultural pests of fruit crops. The first of the five sections defines "pest" and "weed" and generally introduces different kinds of pests in the categories of insects, weeds,…

Effect of new auxin herbicide formulations on control of herbicide resistant weeds and on microbial activities in the rhizosphere

USDA-ARS?s Scientific Manuscript database

Widespread distribution of glyphosate-resistant weeds in soybean-growing areas across Mississippi has economically affected soybean planting and follow-up crop management operations. New multiple herbicide-resistant crop (including soybean) technologies with associated formulations will soon be comm...

Evaluating mustard seed meal for weed suppression in potato (Solanum tuberosum)

USDA-ARS?s Scientific Manuscript database

Mustard seed meal (MSM) derived from Sinapis alba controls weeds for several weeks following application to soil, but also has potential to injure the planted crop. Producers of certified organic potatoes typically utilize a combination of cover crops, soil hilling, harrowing, and cultivation for we...

Glyphosate and dicamba herbicide tank mixture effects on native plant and non-genetically engineered soybean seedlings

EPA Science Inventory

Weed species are becoming resistant to intensive and extensive use of specific herbicides associated with the production of herbicide resistant crops, e.g., the use of glyphosate for weed management with glyphosate resistant soybeans. To counter this resistance, crops engineered ...

Elucidating the apparent maize tolerance to weed competition in long-term organically managed systems

USDA-ARS?s Scientific Manuscript database

In a long-term cropping systems trial comparing organically and conventionally managed systems, organic maize production sustained crop yields equal to conventional methods despite higher weed levels. In 2005 and 2006, an experiment nested within the trial was conducted to analyze the mechanisms und...

Genomics of compositae weeds: EST libraries, microarrays, and evidence of introgression

USDA-ARS?s Scientific Manuscript database

• Premise of Study: Weeds cause considerable environmental and economic damage. However, genomic characterization of weeds has lagged behind that of model plants and crop species. Here we report on the development of genomic tools and resources for 11 weeds from the Compositae family that can serve ...

Pseudomonas syringae pv. phaseolicola isolated from weeds in bean crop fields.

PubMed

Fernández-Sanz, A M; Rodicio, M R; González, A J

2016-04-01

Pseudomonas syringae pv. phaseolicola, the causative agent of halo blight in common bean (Phaseolus vulgaris L.), was isolated from weeds associated with bean crops in Spain. The bacterium was recovered from Fumaria sp, Mercurialis annua, Solanum nigrum and Sonchus oleraceus. Ps. s. pv. phaseolicola had previously been isolated from leguminous plants and S. nigrum, but to our knowledge, this is the first time it was recovered from the other three species. The isolates were phenotypically and genetically characterized, and they were compared with isolates recovered from common beans. Five different genotypic profiles were detected by PmeI-PFGE, two of them being of new description. Weed isolates were as pathogenic on bean plants as bean isolates, but they were not pathogenic on S. nigrum. Regarding the survival of the pathogen in weeds, Ps. s. pv. phaseolicola was isolated from So. oleraceus 11 weeks after the end of the bean crop. These results strongly support the idea of weeds as a potential source of inoculum for halo blight in bean. It has traditionally been considered that the main source of inoculum of Pseudomonas syringae pv. phaseolicola causing halo blight disease in Phaseolus vulgaris are the bean seeds, and that the host range of the bacterium is almost restricted to leguminous plants. In this study, the bacterium was recovered from four nonleguminous weed species collected in bean fields, and its permanence in weeds for at least 11 weeks after the harvesting of the beans was demonstrated. We have also proved that the strains isolated from weeds were pathogenic on bean plants. Accordingly, the host range of Ps. s. pv. phaseolicola could be broader than previously thought and weeds appear to be acting as a reservoir of the pathogen until the next crop. © 2016 The Society for Applied Microbiology.

Interaction of femtosecond laser pulses with plants: towards distinguishing weeds and crops using plasma temperature

NASA Astrophysics Data System (ADS)

Kunz, Jeremy N.; Voronine, Dmitri V.; Ko, Brian A.; Lee, Ho Wai Howard; Rana, Aman; Bagavathiannan, Muthukumar V.; Sokolov, Alexei V.; Scully, Marlan O.

2017-05-01

The ability to distinguish between crops and weeds using sensors from a distance will greatly benefit the farming community through improved and efficient scouting for weeds, reduced herbicide input costs and improved profitability. In the present study, we examined the utility of femtosecond laser-induced breakdown spectroscopy (LIBS) for plant species differentiation. Greenhouse-grown plants of dallisgrass, wheat, soybean and bell pepper were evaluated using LIBS under an ambient environment. LIBS experiments were performed on the leaf samples of different plant species using a femtosecond laser system with an inexpensive lightweight detector. Temperatures of laser-induced plasma in plants depend on many parameters and were determined for each of the study species by the constituent elements interacting with femtosecond laser pulses. Using elemental calcium transitions in plant tissue samples to measure plasma temperatures, we report consistent differences among the four study species, with average values ranging from 5090 ± 168 K (soybean) to 5647 ± 223 K (dallisgrass).

Development of remote sensing based site specific weed management for Midwest mint production

NASA Astrophysics Data System (ADS)

Gumz, Mary Saumur Paulson

Peppermint and spearmint are high value essential oil crops in Indiana, Michigan, and Wisconsin. Although the mints are profitable alternatives to corn and soybeans, mint production efficiency must improve in order to allow industry survival against foreign produced oils and synthetic flavorings. Weed control is the major input cost in mint production and tools to increase efficiency are necessary. Remote sensing-based site-specific weed management offers potential for decreasing weed control costs through simplified weed detection and control from accurate site specific weed and herbicide application maps. This research showed the practicability of remote sensing for weed detection in the mints. Research was designed to compare spectral response curves of field grown mint and weeds, and to use these data to develop spectral vegetation indices for automated weed detection. Viability of remote sensing in mint production was established using unsupervised classification, supervised classification, handheld spectroradiometer readings and spectral vegetation indices (SVIs). Unsupervised classification of multispectral images of peppermint production fields generated crop health maps with 92 and 67% accuracy in meadow and row peppermint, respectively. Supervised classification of multispectral images identified weed infestations with 97% and 85% accuracy for meadow and row peppermint, respectively. Supervised classification showed that peppermint was spectrally distinct from weeds, but the accuracy of these measures was dependent on extensive ground referencing which is impractical and too costly for on-farm use. Handheld spectroradiometer measurements of peppermint, spearmint, and several weeds and crop and weed mixtures were taken over three years from greenhouse grown plants, replicated field plots, and production peppermint and spearmint fields. Results showed that mints have greater near infrared (NIR) and lower green reflectance and a steeper red edge slope than all weed species. These distinguishing characteristics were combined to develop narrow band and broadband spectral vegetation indices (SVIs, ratios of NIR/green reflectance), that were effective in differentiating mint from key weed species. Hyperspectral images of production peppermint and spearmint fields were then classified using SVI-based classification. Narrowband and broadband SVIs classified early season peppermint and spearmint with 64 to 100% accuracy compared to 79 to 100% accuracy for supervised classification of multispectral images of the same fields. Broadband SVIs have potential for use as an automated spectral indicator for weeds in the mints since they require minimal ground referencing and can be calculated from multispectral imagery which is cheaper and more readily available than hyperspectral imagery. This research will allow growers to implement remote sensing based site specific weed management in mint resulting in reduced grower input costs and reduced herbicide entry into the environment and will have applications in other specialty and meadow crops.

Weed control using ammonium nonanoate and cultivation in organic Vidalia sweet onion production

USDA-ARS?s Scientific Manuscript database

Ammonium nonanoate is registered for weed control in certified organic crop production and may be useful to control cool-season weeds in organic Vidalia® sweet onion. Cultivation with a tine weeder has been identified as a cost-effective means of weed control, but delays in cultivation cause some w...

Weed competition with soybean in no-tillage agroforestry and sole-crop systems in subtropical Brazil

USDA-ARS?s Scientific Manuscript database

Weed competition on soybean [Glycine max (L.) Merr.] growth and yield was expected to be different when managed in an agroforestry system as compared with solecropping without trees. Therefore agronomic practices to control weeds might need to be modified in agroforestry systems. We analyzed weed co...

Changes in the weed species composition of the southern US: 1995 to 2009

USDA-ARS?s Scientific Manuscript database

Changes in the weed flora of crops reflect not only the influx and losses to the soil seedbank, but also the management impacts. This analysis documents the changes in the weed flora of the 14 contiguous states comprising the Southern Weed Science Society since the advent of transgenic, herbicide re...

Annual warm-season grasses vary for forage yield, quality, and competitiveness with weeds

USDA-ARS?s Scientific Manuscript database

Warm-season annual grasses may be suitable as herbicide-free forage crops. A two-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three war...

Iowa Commercial Pesticide Applicator Manual, Category 1A: Agricultural Weed Control.

ERIC Educational Resources Information Center

Jennings, Vivan M.; Ryan, Stephen O.

This manual provides information needed to meet the standards for pesticide applicator certification. Weeds, their effects, and control in relation to crop production are presented. Pre- and post-emergence treatments are discussed for row crops such as corn and soybeans. Problems with herbicide application to grass pastures, small grains, and…

High Residue Winter Cover Crops Deplete Winter Annual Weed Seed Across a Landscape in a Long-Term Tillage Study

USDA-ARS?s Scientific Manuscript database

High residue conservation agriculture systems have the potential to maximize environmental benefits achieved when practicing reduced tillage. A greenhouse study was conducted in 2006 through 2008 to determine the effects of cover crop residue on weed seed density within the soil seedbank under varyi...

Weed hosts and relative weed and cover crop susceptibility to Rotylenchulus reniformis in the Mississippi Delta

USDA-ARS?s Scientific Manuscript database

The reniform nematode (Rotylenchulus reniformis) causes economic losses in cotton and soybean in the southeastern United States, and has the ability to reproduce on more than 300 plant species. Even when the host crop is protected through the use of nematicides or host plant resistance, the potentia...

Impact of preceding crop on alfalfa competitiveness with weeds

USDA-ARS?s Scientific Manuscript database

Organic producers would like to include no-till practices in their farming systems. We are seeking to develop a continuous no-till system for organic farming, based on a complex rotation that includes a 3-year sequence of alfalfa. In this study, we evaluated impact of preceding crop on weed infest...

Cover crops increase foraging activity of omnivorous predators in seed patches and facilitate weed biological control

USDA-ARS?s Scientific Manuscript database

Omnivores are important consumers of both weed seeds and insect pests, and habitat provisions like cover crops are suggested to promote their ecosystem services in agricultural systems. However, few studies establish direct links between cover, food, and pest suppression because they are entangled a...

Evaluation of weed control efficacy and crop safety of the new HPPD-inhibiting herbicide-QYR301.

PubMed

Wang, Hengzhi; Liu, Weitang; Zhao, Kongping; Yu, Hui; Zhang, Jia; Wang, Jinxin

2018-05-21

QYR301, 1,3-Dimethyl-1H-pyrazole-4-carboxylic acid 4-[2-chloro-3-(3,5-dimethyl-pyrazol-1-ylmethyl)-4-methanesulfonyl-benzoyl]-2,5-dimethyl-2H-pyrazol-3-yl ester, is a novel HPPD-inhibiting herbicide and was evaluated to provide a reference for post-emergence (POST) application under greenhouse and field conditions. The crop safety (180 and 360 g active ingredient (a.i.) ha -1 treatments) experiment revealed that wheat, paddy, garlic and corn were the only four crops without injury at both examined herbicide rates. The weed control efficacy (60 and 120 g a.i. ha -1 ) experiment showed that QYR301 exhibited high efficacy against many weeds, especially weeds infesting paddy fields. Furthermore, it is interesting that both susceptible and multiple herbicide resistant Echinochloa crus-galli (L.) Beauv. and Echinochloa phyllopogon (Stapf) Koss, two notorious weed species in paddy field, remained susceptible to QYR301. Further crop tolerance results indicated that 20 tested paddy hybrids displayed different levels of tolerance to QYR301, with the japonica paddy hybrids having more tolerance than indica paddy hybrids under greenhouse conditions. Results obtained from field experiments showed that QYR301 POST at 135 to 180 g a.i. ha -1 was recommended to provide satisfactory full-season control of E. crus-galli and Leptochloa chinensis (L.) Nees and to maximize rice yields. These findings indicate that QYR301 possesses great potential for the management of weeds in paddy fields.

Weed seed resources for birds in fields with contrasting conventional and genetically modified herbicide-tolerant crops

PubMed Central

Gibbons, David W; Bohan, David A; Rothery, Peter; Stuart, Rick C; Haughton, Alison J; Scott, Rod J; Wilson, Jeremy D; Perry, Joe N; Clark, Suzanne J; Dawson, Robert J.G; Firbank, Les G

2006-01-01

The UK Farm Scale Evaluations (FSEs) have shown that the use of broad spectrum herbicides on genetically modified herbicide-tolerant (GMHT) crops can have dramatic effects on weed seed production compared to management of conventional varieties. Here, we use FSE data and information on bird diets to determine how GMHT cropping might change the food resources available to farmland birds. More than 60 fields of each of four crops, spring- and winter-sown oilseed rape, beet and maize, were split, one half being sown with a conventional variety, the other with a GMHT variety. Seed rain from weeds known to be important in the diets of 17 granivorous farmland bird species was measured under the two treatments. In beet and spring oilseed rape, rain of weed seeds important in the diets of 16 bird species was significantly reduced in GMHT compared to conventional halves; for no species did it increase. In winter oilseed rape, rain of weed seeds important in the diets of 10 species was significantly reduced in GMHT halves; for only one species did it increase significantly. By contrast, in maize, rain of weed seeds important in the diets of seven species was significantly greater in GMHT halves; for no species was it reduced. Treatment effects for the total weed seed energy available to each bird species were very similar to those for seed rain alone. Measuring the effects on individual bird species was outside the scope of this study. Despite this, these results suggest that should beet, spring and winter rape crops in the UK be largely replaced by GMHT varieties and managed as in the FSEs, this would markedly reduce important food resources for farmland birds, many of which declined during the last quarter of the twentieth century. By contrast, GMHT maize would be beneficial to farmland birds. PMID:16822753

Discrimination of crop and weeds on visible and visible/near-infrared spectrums using support vector machines, artificial neural network and decision tree

USDA-ARS?s Scientific Manuscript database

Weeds are regarded as farmers' natural enemy. In order to avoid excessive pesticide residues, the destruction of ecological environment, and to guarantee the quality and safety of agricultural products, it is urgent to develop highly-efficient weed management methods. Amongst, weed discrimination is...

Rice hull mulch affects germination of bittercress and creeping woodsorrel in container plant culture

USDA-ARS?s Scientific Manuscript database

Mulches are commonly used to control weeds in container nursery crops, especially in sites where preemergence herbicides are either not labeled or potentially phytotoxic to the crop. Parboiled rice hulls have been shown to provide effective weed control when applied 1.25 to 2.5 cm deep over the con...

Rolled-crimped winter rye cover effects on hand-weeding times and fruit yield and quality of cucurbits

USDA-ARS?s Scientific Manuscript database

Fruit and vegetables produced without pesticides are in demand by some segments of society. However, weeds often are deleterious in such crops, and managing them without herbicides is difficult. Stale seedbeds and rolled-crimped winter rye cover crops are non-chemical methods that may help manage we...

Comparison of SVM RBF-NN and DT for crop and weed identification based on spectral measurement over corn fields

USDA-ARS?s Scientific Manuscript database

It is important to find an appropriate pattern-recognition method for in-field plant identification based on spectral measurement in order to classify the crop and weeds accurately. In this study, the method of Support Vector Machine (SVM) was evaluated and compared with two other methods, Decision ...

High residue cover crops alone or with strategic tillage to manage glyphosate-resistant palmer amaranth (amaranthus palmeri) in Southeastern cotton (gossypium hirsutum)

USDA-ARS?s Scientific Manuscript database

Glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Wats) is redefining row crop weed management in the Southeast due to its widespread distribution, high competitive ability, copious seed production, and resilience to standard weed management programs. Herbicides alone are failing to p...

A fully convolutional network for weed mapping of unmanned aerial vehicle (UAV) imagery.

PubMed

Huang, Huasheng; Deng, Jizhong; Lan, Yubin; Yang, Aqing; Deng, Xiaoling; Zhang, Lei

2018-01-01

Appropriate Site Specific Weed Management (SSWM) is crucial to ensure the crop yields. Within SSWM of large-scale area, remote sensing is a key technology to provide accurate weed distribution information. Compared with satellite and piloted aircraft remote sensing, unmanned aerial vehicle (UAV) is capable of capturing high spatial resolution imagery, which will provide more detailed information for weed mapping. The objective of this paper is to generate an accurate weed cover map based on UAV imagery. The UAV RGB imagery was collected in 2017 October over the rice field located in South China. The Fully Convolutional Network (FCN) method was proposed for weed mapping of the collected imagery. Transfer learning was used to improve generalization capability, and skip architecture was applied to increase the prediction accuracy. After that, the performance of FCN architecture was compared with Patch_based CNN algorithm and Pixel_based CNN method. Experimental results showed that our FCN method outperformed others, both in terms of accuracy and efficiency. The overall accuracy of the FCN approach was up to 0.935 and the accuracy for weed recognition was 0.883, which means that this algorithm is capable of generating accurate weed cover maps for the evaluated UAV imagery.

Post-directed weed control in bell peppers

USDA-ARS?s Scientific Manuscript database

Organic pepper (Capsicum annuum L.) producers need appropriate herbicides that can effectively provide post-emergent weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of a potential organic herbicide on weed control efficacy, crop injury, an...

UAV low-altitude remote sensing for precision weed management

USDA-ARS?s Scientific Manuscript database

Precision weed management, an application of precision agriculture, accounts for within-field variability of weed infestation and herbicide damage. Unmanned aerial vehicles (UAVs) provide a unique platform for remote sensing of field crops. They are more efficient and flexible than manned agricultur...

Combining novel monitoring tools and precision application technologies for integrated high-tech crop protection in the future (a discussion document).

PubMed

Zijlstra, Carolien; Lund, Ivar; Justesen, Annemarie F; Nicolaisen, Mogens; Jensen, Peter Kryger; Bianciotto, Valeria; Posta, Katalin; Balestrini, Raffaella; Przetakiewicz, Anna; Czembor, Elzbieta; van de Zande, Jan

2011-06-01

The possibility of combining novel monitoring techniques and precision spraying for crop protection in the future is discussed. A generic model for an innovative crop protection system has been used as a framework. This system will be able to monitor the entire cropping system and identify the presence of relevant pests, diseases and weeds online, and will be location specific. The system will offer prevention, monitoring, interpretation and action which will be performed in a continuous way. The monitoring is divided into several parts. Planting material, seeds and soil should be monitored for prevention purposes before the growing period to avoid, for example, the introduction of disease into the field and to ensure optimal growth conditions. Data from previous growing seasons, such as the location of weeds and previous diseases, should also be included. During the growing season, the crop will be monitored at a macroscale level until a location that needs special attention is identified. If relevant, this area will be monitored more intensively at a microscale level. A decision engine will analyse the data and offer advice on how to control the detected diseases, pests and weeds, using precision spray techniques or alternative measures. The goal is to provide tools that are able to produce high-quality products with the minimal use of conventional plant protection products. This review describes the technologies that can be used or that need further development in order to achieve this goal. Copyright © 2011 Society of Chemical Industry.

WEED SURVEYING OF PHACELIA (PHACELIA TANACETIFOLIA L.) AND EVALUATING THE EFFICIENCY OF THE WEED CONTROL.

PubMed

Horváth, E; Szabó, R

2014-01-01

The experiment was set up in an area of 9 ha that was split into 4 plots: in plot 1 the row spacing was 12 cm and the seeding rate was 10 kg; in plot 2 the row spacing was 24 cm and the seeding rate was 10 kg; in plot 3 the row spacing was 24 cm and the seeding rate was 8 kg; in plot 4 the row spacing was 12 cm and the seeding rate was 8 kg. After the weed surveying, the total weed coverage was established as follows: in plot 1 the total weed coverage was 11.34%, in plot 2 it was 12.3%, in plot 3 it was 18%, and in plot 4 the total weed coverage was 15%. Based on the weed survey, on the test area the following dicotyledon weeds belonging to the T4 Raunkiaer plant life-form category occupied the highest percentage: heal-all, black-bindweed, goosefoot. The proportion of the perennial dicotyledons: field bindweed (G3), tuberous pea (G1), white campion (H3) was negligible. In all four cases the weed control was executed using the same herbicide in the same doses and with regard to the weed species it showed the same level of efficiency. The smaller row spacing and higher seeding rate has a beneficial effect on the weed suppressing capacity of the crop, the crop's weed suppressing capacity is better and the development of the weeds becomes worse.

The evolution of flowering strategies in US weedy rice.

PubMed

Thurber, Carrie S; Reagon, Michael; Olsen, Kenneth M; Jia, Yulin; Caicedo, Ana L

2014-10-01

• Local adaptation in plants often involves changes in flowering time in response to day length and temperature. Many crops have been selected for uniformity in flowering time. In contrast, variable flowering may be important for increased competitiveness in weed species invading the agricultural environment. Given the shared species designation of cultivated rice (Oryza sativa) and its the invasive conspecific weed, weedy rice, we assessed the extent to which flowering time differed between these groups. We further assessed whether genes affecting flowering time variation in rice could play a role in the evolution of weedy rice in the United States.• We quantified flowering time under day-neutral conditions in weedy, cultivated, and wild Oryza groups. We also sequenced two candidate gene regions: Hd1, a locus involved in promotion of flowering under short days, and the promoter of Hd3a, a locus encoding the mobile signal that induces flowering.• We found that flowering time has diverged between two distinct weedy rice groups, such that straw-hull weeds tend to flower earlier and black-hull awned weeds tend to flower later than cultivated rice. These differences are consistent with weed Hd1 alleles. At both loci, weeds share haplotypes with their cultivated progenitors, despite significantly different flowering times.• Our phenotypic data indicate the existence of multiple flowering strategies in weedy rice. Flowering differences between weeds and ancestors suggest this trait has evolved rapidly. From a weed management standpoint, there is the potential for overlap in flowering of black-hull awned weeds and crops in the United States, permitting hybridization and the potential escape of genes from crops. © 2014 Botanical Society of America, Inc.

Global perspective of herbicide-resistant weeds.

PubMed

Heap, Ian

2014-09-01

Two hundred and twenty weed species have evolved resistance to one or more herbicides, and there are now 404 unique cases (species × site of action) of herbicide-resistant weeds globally. ALS inhibitor-resistant weeds account for about a third of all cases (133/404) and are particularly troublesome in rice and cereals. Although 71 weed species have been identified with triazine resistance, their importance has dwindled with the shift towards Roundup Ready® crops in the USA and the reduction of triazine usage in Europe. Forty-three grasses have evolved resistance to ACCase inhibitors, with the most serious cases being Avena spp., Lolium spp., Phalaris spp., Setaria spp. and Alopecurus myosuroides, infesting more than 25 million hectares of cereal production globally. Of the 24 weed species with glyphosate resistance, 16 have been found in Roundup Ready® cropping systems. Although Conyza canadensis is the most widespread glyphosate-resistant weed, Amaranthus palmeri and Amaranthus tuberculartus are the two most economically important glyphosate-resistant weeds because of the area they infest and the fact that these species have evolved resistance to numerous other herbicide sites of action, leaving growers with few herbicidal options for their control. The agricultural chemical industry has not brought any new herbicides with novel sites of action to market in over 30 years, making growers reliant on using existing herbicides in new ways. In addition, tougher registration and environmental regulations on herbicides have resulted in a loss of some herbicides, particularly in Europe. The lack of novel herbicide chemistries being brought to market combined with the rapid increase in multiple resistance in weeds threatens crop production worldwide. © 2013 Society of Chemical Industry.

Panel Discussion: Using Shielded Sprayers to Control Weeds in Nursery Beds

Treesearch

Dwight H. Stallard

2005-01-01

Shielded sprayers have proven to be more effective than mechanical-type machines at controlling weeds in hardwood crops. Hand weeding times are reduced significantly, lowering costs and saving time for nursery personnel to do other jobs.Individual papers from this publication

Herbicides as weed control agents: state of the art: I. Weed control research and safener technology: the path to modern agriculture.

PubMed

Kraehmer, Hansjoerg; Laber, Bernd; Rosinger, Chris; Schulz, Arno

2014-11-01

The purpose of modern industrial herbicides is to control weeds. The species of weeds that plague crops today are a consequence of the historical past, being related to the history of the evolution of crops and farming practices. Chemical weed control began over a century ago with inorganic compounds and transitioned to the age of organic herbicides. Targeted herbicide research has created a steady stream of successful products. However, safeners have proven to be more difficult to find. Once found, the mode of action of the safener must be determined, partly to help in the discovery of further compounds within the same class. However, mounting regulatory and economic pressure has changed the industry completely, making it harder to find a successful herbicide. Herbicide resistance has also become a major problem, increasing the difficulty of controlling weeds. As a result, the development of new molecules has become a rare event today. © 2014 American Society of Plant Biologists. All Rights Reserved.

Herbicides as Weed Control Agents: State of the Art: I. Weed Control Research and Safener Technology: The Path to Modern Agriculture

PubMed Central

Kraehmer, Hansjoerg; Laber, Bernd; Rosinger, Chris; Schulz, Arno

2014-01-01

The purpose of modern industrial herbicides is to control weeds. The species of weeds that plague crops today are a consequence of the historical past, being related to the history of the evolution of crops and farming practices. Chemical weed control began over a century ago with inorganic compounds and transitioned to the age of organic herbicides. Targeted herbicide research has created a steady stream of successful products. However, safeners have proven to be more difficult to find. Once found, the mode of action of the safener must be determined, partly to help in the discovery of further compounds within the same class. However, mounting regulatory and economic pressure has changed the industry completely, making it harder to find a successful herbicide. Herbicide resistance has also become a major problem, increasing the difficulty of controlling weeds. As a result, the development of new molecules has become a rare event today. PMID:25104723

Critical period of weed control in winter canola (Brassica napus L.) in a semi-arid region.

PubMed

Aghaalikhani, M; Yaghoobi, S R

2008-03-01

In order to determine the critical period of weed control in winter canola (Brassica napus L. cv. Okapi) an experiment was carried out at research field of Tarbiat Modarres University, Tehran, Iran on 2004-2005 growing season. Fourteen experimental treatments which divided into two sets were arranged in Randomized complete blocks design with four replications. In the first set, the crop was kept weed-free from emergence time to two-leaf stage (V2), four-leaf stage (V4), six-leaf stage (V6), eight-leaf stage (V8), early flowering (IF), 50% of silique set (50% SS) and final harvest (H). In the second set, weeds where permitted to grow with the crop until above mentioned stages. In this study critical period of weed control was determined according to evaluate seed bank emerged weed biomass effect on canola grain yield loss using Gompertz and logistic equations. Result showed a critical time of weed control about 25 days after emergence (between four to six-leaf stages) with 5% accepted yield loss. Therefore, weed control in this time could provide the best result and avoid yield loss and damage to agroecosystem.

A review of the potential for competitive cereal cultivars as a tool in integrated weed management.

PubMed

Andrew, I K S; Storkey, J; Sparkes, D L

2015-06-01

Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide-resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade-offs between competitive ability and yield in weed-free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple-to-use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.

Growth environment but not seed position on the parent plant affect seed germination of two Thlaspi arvense L. populations

USDA-ARS?s Scientific Manuscript database

Thlaspi arvense L. is a common weed found in most temperate regions throughout the world that also shows excellent potential for domestication as an oilseed crop. The complexity of T. arvense seed dormancy presently makes it difficult to manage as a weed or oilseed crop. Therefore, a better understa...

Introduction to Agronomy, Grain Crops, Weeds and Controls. A Learning Activity Pac in Agricultural Education Courses in Wisconsin.

ERIC Educational Resources Information Center

Wisconsin State Dept. of Public Instruction, Madison. Div. of Instructional Services.

This learning activity pac contains information to help the teachers of high school vocational agriculture in the instructional area of agronomy. Each of the two main sections, grain crops and weeds and controls, includes teacher and student units for the section lessons. Teacher units include special instructions--equipment needed (film…

Allelopathy in crop/weed interactions--an update.

PubMed

Belz, Regina G

2007-04-01

Since varietal differences in allelopathy of crops against weeds were discovered in the 1970s, much research has documented the potential that allelopathic crops offer for integrated weed management with substantially reduced herbicide rates. Research groups worldwide have identified several crop species possessing potent allelopathic interference mediated by root exudation of allelochemicals. Rice, wheat, barley and sorghum have attracted most attention. Past research focused on germplasm screening for elite allelopathic cultivars and the identification of the allelochemicals involved. Based on this, traditional breeding efforts were initiated in rice and wheat to breed agronomically acceptable, weed-suppressive cultivars with improved allelopathic interference. Promising suppressive crosses are under investigation. Molecular approaches have elucidated the genetics of allelopathy by QTL mapping which associated the trait in rice and wheat with several chromosomes and suggested the involvement of several allelochemicals. Potentially important compounds that are constitutively secreted from roots have been identified in all crop species under investigation. Biosynthesis and exudation of these metabolites follow a distinct temporal pattern and can be induced by biotic and abiotic factors. The current state of knowledge suggests that allelopathy involves fluctuating mixtures of allelochemicals and their metabolites as regulated by genotype and developmental stage of the producing plant, environment, cultivation and signalling effects, as well as the chemical or microbial turnover of compounds in the rhizosphere. Functional genomics is being applied to identify genes involved in biosynthesis of several identified allelochemicals, providing the potential to improve allelopathy by molecular breeding. The dynamics of crop allelopathy, inducible processes and plant signalling is gaining growing attention; however, future research should also consider allelochemical release mechanisms, persistence, selectivity and modes of action, as well as consequences of improved crop allelopathy on plant physiology, the environment and management strategies. Creation of weed-suppressive cultivars with improved allelopathic interference is still a challenge, but traditional breeding or biotechnology should pave the way.

Broomrape Weeds. Underground Mechanisms of Parasitism and Associated Strategies for their Control: A Review

PubMed Central

Fernández-Aparicio, Mónica; Reboud, Xavier; Gibot-Leclerc, Stephanie

2016-01-01

Broomrapes are plant-parasitic weeds which constitute one of the most difficult-to-control of all biotic constraints that affect crops in Mediterranean, central and eastern Europe, and Asia. Due to their physical and metabolic overlap with the crop, their underground parasitism, their achlorophyllous nature, and hardly destructible seed bank, broomrape weeds are usually not controlled by management strategies designed for non-parasitic weeds. Instead, broomrapes are in current state of intensification and spread due to lack of broomrape-specific control programs, unconscious introduction to new areas and may be decline of herbicide use and global warming to a lesser degree. We reviewed relevant facts about the biology and physiology of broomrape weeds and the major feasible control strategies. The points of vulnerability of some underground events, key for their parasitism such as crop-induced germination or haustorial development are reviewed as inhibition targets of the broomrape-crop association. Among the reviewed strategies are those aimed (1) to reduce broomrape seed bank viability, such as fumigation, herbigation, solarization and use of broomrape-specific pathogens; (2) diversion strategies to reduce the broomrape ability to timely detect the host such as those based on promotion of suicidal germination, on introduction of allelochemical interference, or on down-regulating host exudation of germination-inducing factors; (3) strategies to inhibit the capacity of the broomrape seedling to penetrate the crop and connect with the vascular system, such as biotic or abiotic inhibition of broomrape radicle growth and crop resistance to broomrape penetration either natural, genetically engineered or elicited by biotic- or abiotic-resistance-inducing agents; and (4) strategies acting once broomrape seedling has bridged its vascular system with that of the host, aimed to impede or to endure the parasitic sink such as those based on the delivery of herbicides via haustoria, use of resistant or tolerant varieties and implementation of cultural practices improving crop competitiveness. PMID:26925071

Trait-based characterisation of soil exploitation strategies of banana, weeds and cover plant species

PubMed Central

Tardy, Florence; Damour, Gaëlle; Dorel, Marc; Moreau, Delphine

2017-01-01

Cover plants can be introduced in cropping systems to provide agroecosystem services, including weed control via competition for resources. There is currently no consensus on how to identify the best cover plant species, while trait-based approaches are promising for screening plant species due to their agroecosystem service provision potential. This study was carried out to characterize soil exploitation strategies of cover plant species in banana agroecosystems using a trait-based approach, and in turn identify cover plant species with a high weed control potential via competition for soil resources in banana cropping systems. A field experiment was conducted on 17 cover plant species, two weed species and two banana cultivars grown individually. Four functional traits were measured. Two of them (i.e., the size of the zone explored by roots and the root impact density) were used to characterize root system soil exploration patterns. Two other traits (i.e., specific root length and root diameter) were used to characterize resource acquisition within the soil zone explored by the roots. All studied traits exhibited marked variations among species. The findings suggested a trade-off between the abilities of species to develop a limited number of large diameter roots exploring a large soil zone versus many thin roots exploring a smaller soil zone. Three soil-resource exploitation strategies were identified among species: (i) with large diameter roots that explore a large soil zone; (ii) with small diameter roots and a high specific length that explore a smaller soil zone; and (iii) with a high total root-impact density and an intermediate specific root length that explore the uppermost soil layers. Interestingly, in our panel of species, no correlations with regard to belowground and aboveground strategies were noted: species with an acquisitive belowground strategy could display an acquisitive or a conservative aboveground strategy. The findings of this study illustrated that a trait-based approach could be used to identify plant species with potential for competing with weeds, while minimising competition with banana. Six of the 17 studied cover crop species were identified as having this potential. The next step will be to assess them for their weed control performances in banana cropping systems with low reliance on herbicides. PMID:28257454

Trait-based characterisation of soil exploitation strategies of banana, weeds and cover plant species.

PubMed

Tardy, Florence; Damour, Gaëlle; Dorel, Marc; Moreau, Delphine

2017-01-01

Cover plants can be introduced in cropping systems to provide agroecosystem services, including weed control via competition for resources. There is currently no consensus on how to identify the best cover plant species, while trait-based approaches are promising for screening plant species due to their agroecosystem service provision potential. This study was carried out to characterize soil exploitation strategies of cover plant species in banana agroecosystems using a trait-based approach, and in turn identify cover plant species with a high weed control potential via competition for soil resources in banana cropping systems. A field experiment was conducted on 17 cover plant species, two weed species and two banana cultivars grown individually. Four functional traits were measured. Two of them (i.e., the size of the zone explored by roots and the root impact density) were used to characterize root system soil exploration patterns. Two other traits (i.e., specific root length and root diameter) were used to characterize resource acquisition within the soil zone explored by the roots. All studied traits exhibited marked variations among species. The findings suggested a trade-off between the abilities of species to develop a limited number of large diameter roots exploring a large soil zone versus many thin roots exploring a smaller soil zone. Three soil-resource exploitation strategies were identified among species: (i) with large diameter roots that explore a large soil zone; (ii) with small diameter roots and a high specific length that explore a smaller soil zone; and (iii) with a high total root-impact density and an intermediate specific root length that explore the uppermost soil layers. Interestingly, in our panel of species, no correlations with regard to belowground and aboveground strategies were noted: species with an acquisitive belowground strategy could display an acquisitive or a conservative aboveground strategy. The findings of this study illustrated that a trait-based approach could be used to identify plant species with potential for competing with weeds, while minimising competition with banana. Six of the 17 studied cover crop species were identified as having this potential. The next step will be to assess them for their weed control performances in banana cropping systems with low reliance on herbicides.

A novel 5-enolpyruvoylshikimate-3-phosphate (EPSP) synthase transgene for glyphosate resistance stimulates growth and fecundity in weedy rice (Oryza sativa) without herbicide

PubMed Central

Wang, Wei; Xia, Hui; Yang, Xiao; Xu, Ting; Si, Hong Jiang; Cai, Xing Xing; Wang, Feng; Su, Jun; Snow, Allison A; Lu, Bao-Rong

2014-01-01

Understanding evolutionary interactions among crops and weeds can facilitate effective weed management. For example, gene flow from crops to their wild or weedy relatives can lead to rapid evolution in recipient populations. In rice (Oryza sativa), transgenic herbicide resistance is expected to spread to conspecific weedy rice (Oryza sativa f. spontanea) via hybridization. Here, we studied fitness effects of transgenic over-expression of a native 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) gene developed to confer glyphosate resistance in rice. Controlling for genetic background, we examined physiological traits and field performance of crop–weed hybrid lineages that segregated for the presence or absence of this novel epsps transgene. Surprisingly, we found that transgenic F2 crop–weed hybrids produced 48–125% more seeds per plant than nontransgenic controls in monoculture- and mixed-planting designs without glyphosate application. Transgenic plants also had greater EPSPS protein levels, tryptophan concentrations, photosynthetic rates, and per cent seed germination compared with nontransgenic controls. Our findings suggest that over-expression of a native rice epsps gene can lead to fitness advantages, even without exposure to glyphosate. We hypothesize that over-expressed epsps may be useful to breeders and, if deployed, could result in fitness benefits in weedy relatives following transgene introgression. PMID:23905647

Quantifying efficacy and limits of unmanned aerial vehicle (UAV) technology for weed seedling detection as affected by sensor resolution.

PubMed

Peña, José M; Torres-Sánchez, Jorge; Serrano-Pérez, Angélica; de Castro, Ana I; López-Granados, Francisca

2015-03-06

In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early detection of weed seedlings. The ability to discriminate weeds was significantly affected by the imagery spectral (type of camera), spatial (flight altitude) and temporal (the date of the study) resolutions. The colour-infrared images captured at 40 m and 50 days after sowing (date 2), when plants had 5-6 true leaves, had the highest weed detection accuracy (up to 91%). At this flight altitude, the images captured before date 2 had slightly better results than the images captured later. However, this trend changed in the visible-light images captured at 60 m and higher, which had notably better results on date 3 (57 days after sowing) because of the larger size of the weed plants. Our results showed the requirements on spectral and spatial resolutions needed to generate a suitable weed map early in the growing season, as well as the best moment for the UAV image acquisition, with the ultimate objective of applying site-specific weed management operations.

Quantifying Efficacy and Limits of Unmanned Aerial Vehicle (UAV) Technology for Weed Seedling Detection as Affected by Sensor Resolution

PubMed Central

Peña, José M.; Torres-Sánchez, Jorge; Serrano-Pérez, Angélica; de Castro, Ana I.; López-Granados, Francisca

2015-01-01

In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early detection of weed seedlings. The ability to discriminate weeds was significantly affected by the imagery spectral (type of camera), spatial (flight altitude) and temporal (the date of the study) resolutions. The colour-infrared images captured at 40 m and 50 days after sowing (date 2), when plants had 5–6 true leaves, had the highest weed detection accuracy (up to 91%). At this flight altitude, the images captured before date 2 had slightly better results than the images captured later. However, this trend changed in the visible-light images captured at 60 m and higher, which had notably better results on date 3 (57 days after sowing) because of the larger size of the weed plants. Our results showed the requirements on spectral and spatial resolutions needed to generate a suitable weed map early in the growing season, as well as the best moment for the UAV image acquisition, with the ultimate objective of applying site-specific weed management operations. PMID:25756867

Crop circles and organic weed control

USDA-ARS?s Scientific Manuscript database

Organic vegetable production relies on integrated weed control measures to attain satisfactory weed control. An experiment was established in autumn 2010 and 2011 at the North Alabama Horticulture Experiment Station, Cullman, AL. Plot size at both locations was 2.5 by 6 m containing a single row o...

Impact of over-the-top broadcast applications of Racer® on onion weed control

USDA-ARS?s Scientific Manuscript database

The weed control challenges for onion production are formidable; however, these challenges are even greater for those considering organic crop production. Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Racer (registered trademark) is a poten...

Elymus repens biomass allocation and acquisition as affected by light and nutrient supply and companion crop competition

PubMed Central

Ringselle, Björn; Prieto-Ruiz, Inés; Andersson, Lars; Aronsson, Helena; Bergkvist, Göran

2017-01-01

Background and Aims Competitive crops are a central component of resource-efficient weed control, especially for problematic perennial weeds such as Elymus repens. Competition not only reduces total weed biomass, but denial of resources can also change the allocation pattern – potentially away from the underground storage organs that make perennial weeds difficult to control. Thus, the competition mode of crops may be an important component in the design of resource-efficient cropping systems. Our aim was to determine how competition from companion crops with different modes of competition affect E. repens biomass acquisition and allocation and discuss that in relation to how E. repens responds to different levels of light and nutrient supply. Methods Greenhouse experiments were conducted with E. repens growing in interspecific competition with increasing density of perennial ryegrass or red clover, or growing at three levels of both light and nutrient supply. Key Results Elymus repens total biomass decreased with increasing biomass of the companion crop and the rate of decrease was higher with red clover than with perennial ryegrass, particularly for E. repens rhizome biomass. A reduced nutrient supply shifted E. repens allocation towards below-ground biomass while a reduced light supply shifted it towards shoot biomass. Red clover caused no change in E. repens allocation pattern, while ryegrass mostly shifted the allocation towards below-ground biomass, but the change was not correlated with ryegrass biomass. Conclusions The companion crop mode of competition influences both the suppression rate of E. repens biomass acquisition and the likelihood of shifts in E. repens biomass allocation. PMID:28025285

Taxonomic and life history bias in herbicide resistant weeds: implications for deployment of resistant crops.

PubMed

Holt, Jodie S; Welles, Shana R; Silvera, Katia; Heap, Ian M; Heredia, Sylvia M; Martinez-Berdeja, Alejandra; Palenscar, Kai T; Sweet, Lynn C; Ellstrand, Norman C

2013-01-01

Evolved herbicide resistance (EHR) is an important agronomic problem and consequently a food security problem, as it jeopardizes herbicide effectiveness and increases the difficulty and cost of weed management. EHR in weeds was first reported in 1970 and the number of cases has accelerated dramatically over the last two decades. Despite 40 years of research on EHR, why some weeds evolve resistance and others do not is poorly understood. Here we ask whether weed species that have EHR are different from weeds in general. Comparing taxonomic and life history traits of weeds with EHR to a control group ("the world's worst weeds"), we found weeds with EHR significantly over-represented in certain plant families and having certain life history biases. In particular, resistance is overrepresented in Amaranthaceae, Brassicaceae and Poaceae relative to all weeds, and annuality is ca. 1.5 times as frequent in weeds with EHR as in the control group. Also, for perennial EHR weeds, vegetative reproduction is only 60% as frequent as in the control group. We found the same trends for subsets of weeds with EHR to acetolactate synthase (ALS), photosystem II (PSII), and 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase-inhibitor herbicides and with multiple resistance. As herbicide resistant crops (transgenic or not) are increasingly deployed in developing countries, the problems of EHR could increase in those countries as it has in the USA if the selecting herbicides are heavily applied and appropriate management strategies are not employed. Given our analysis, we make some predictions about additional species that might evolve resistance.

Glyphosate-resistant weeds of South American cropping systems: an overview.

PubMed

Vila-Aiub, Martin M; Vidal, Ribas A; Balbi, Maria C; Gundel, Pedro E; Trucco, Frederico; Ghersa, Claudio M

2008-04-01

Herbicide resistance is an evolutionary event resulting from intense herbicide selection over genetically diverse weed populations. In South America, orchard, cereal and legume cropping systems show a strong dependence on glyphosate to control weeds. The goal of this report is to review the current knowledge on cases of evolved glyphosate-resistant weeds in South American agriculture. The first reports of glyphosate resistance include populations of highly diverse taxa (Lolium multiflorum Lam., Conyza bonariensis L., C. canadensis L.). In all instances, resistance evolution followed intense glyphosate use in fruit fields of Chile and Brazil. In fruit orchards from Colombia, Parthenium hysterophorus L. has shown the ability to withstand high glyphosate rates. The recent appearance of glyphosate-resistant Sorghum halepense L. and Euphorbia heterophylla L. in glyphosate-resistant soybean fields of Argentina and Brazil, respectively, is of major concern. The evolution of glyphosate resistance has clearly taken place in those agroecosystems where glyphosate exerts a strong and continuous selection pressure on weeds. The massive adoption of no-till practices together with the utilization of glyphosate-resistant soybean crops are factors encouraging increase in glyphosate use. This phenomenon has been more evident in Argentina and Brazil. The exclusive reliance on glyphosate as the main tool for weed management results in agroecosystems biologically more prone to glyphosate resistance evolution. Copyright (c) 2007 Society of Chemical Industry.

Tine cultivation effects on weed control, productivity, and economics of peanut under organic management

USDA-ARS?s Scientific Manuscript database

Identifying effective weed control regimes for organic peanut has become paramount for improving the feasibility of organic production. Tine cultivation is a proven effective method at reducing in-row weed populations in several crops. Field trials were therefore conducted in 2008 and 2009 to asse...

Propelled abrasive grit for weed control in organic silage corn

USDA-ARS?s Scientific Manuscript database

Weed management in organic farming requires many strategies to accomplish acceptable control and maintain crop yields. This two-year field study used air propelled abrasive grit for in-row weed control in a silage corn system. Corncob grit was applied as a single application at corn vegetative growt...

Weed control in sweet bell pepper using sequential postdirected applications of pelargonic acid

USDA-ARS?s Scientific Manuscript database

Pepper (Capsicum annuum) producers would benefit from additional herbicide options that are safe to the crop and provide effective weed control. Research was conducted in southeastern Oklahoma (Atoka County, Lane, OK) during 2010 and 2011 to determine the impact of pelargonic acid on weed control ef...

Evaluation of organic alternatives for weed management in pulasan (Nephelium ramboutan-ake)

USDA-ARS?s Scientific Manuscript database

In Puerto Rico, most fruit crop growers use post-emergence synthetic herbicides as a major component of their weed management programs. Organic growers are not allowed to use synthetic herbicides; hence there is a need to develop alternative weed management strategies for current and prospective org...

Biological aspects of weed dynamics in no-till systems

USDA-ARS?s Scientific Manuscript database

Scientists and producers in the Eurasian steppe are interested in no-till crop production, but are concerned that, without tillage, weed density will escalate in croplands. In the United States, producers have used no-till systems for several decades and weed density has not increased. In this pap...

Intercropped watermelon for weed suppression in a low-input organic system.

USDA-ARS?s Scientific Manuscript database

A multi-layered canopy provided by intercropping species with different growth forms can provide barriers for the germination of weed seeds and can allow for a more efficient utilization of resources that reduce competition to target crops from weeds. Intercropping can thus be an effective cultural ...

Nitrogen competition between corn and weeds in soils under organic and conventional management

USDA-ARS?s Scientific Manuscript database

Cropping systems research has shown that organic systems can have comparable yields to conventional systems at higher weed biomass levels. Higher weed tolerance in organic systems could be due to differences in labile soil organic matter and nitrogen (N) mineralization potential. The objective of ou...

Herbicide Safeners Decrease Sensitivity to Herbicides Inhibiting Acetolactate-Synthase and Likely Activate Non-Target-Site-Based Resistance Pathways in the Major Grass Weed Lolium sp. (Rye-Grass)

PubMed Central

Duhoux, Arnaud; Pernin, Fanny; Desserre, Diane; Délye, Christophe

2017-01-01

Herbicides are currently pivotal to control weeds and sustain food security. Herbicides must efficiently kill weeds while being as harmless as possible for crops, even crops taxonomically close to weeds. To increase their selectivity toward crops, some herbicides are sprayed in association with safeners that are bioactive compounds exacerbating herbicide-degrading pathways reputedly specifically in crops. However, exacerbated herbicide metabolism is also a key mechanism underlying evolved non-target-site-based resistance to herbicides (NTSR) in weeds. This raised the issue of a possible role of safeners on NTSR evolution in weeds. We investigated a possible effect of the respective field rates of the two broadly used safeners cloquintocet-mexyl and mefenpyr-diethyl on the sensitivity of the troublesome global weed Lolium sp. (rye-grass) to the major herbicides inhibiting acetolactate-synthase (ALS) pyroxsulam and iodosulfuron + mesosulfuron, respectively. Three Lolium sp. populations were studied in three series of experiments. The first experiment series compared the frequencies of plants surviving application of each herbicide alone or in association with its safener. Safener co-application caused a net increase ranging from 5.0 to 46.5% in the frequency of plants surviving the field rate of their associated herbicide. In a second series of experiments, safener effect was assessed on individual plant sensitivity using vegetative propagation. A reduction in sensitivity to pyroxsulam and to iodosulfuron + mesosulfuron was observed for 44.4 and 11.1% of the plants in co-treatment with cloquintocet-mexyl and mefenpyr-diethyl, respectively. A third series of experiments investigated safener effect on the expression level of 19 Lolium sp. NTSR marker genes. Safeners showed an enhancing effect on the expression level of 10 genes. Overall, we demonstrated that cloquintocet-mexyl and mefenpyr-diethyl both reduced the sensitivity of Lolium sp. to their associated ALS-inhibiting herbicide and most likely exacerbated herbicide-degrading secondary metabolism pathways. This suggests that genetic variation for safener response is present in Lolium sp. Thus, a possible, uninvestigated way to NTSR evolution could be selection for increased responsiveness to safener action. Delivering safeners exclusively to the crop could mitigate the risk for NTSR evolution in weeds. PMID:28848566

Herbicide Safeners Decrease Sensitivity to Herbicides Inhibiting Acetolactate-Synthase and Likely Activate Non-Target-Site-Based Resistance Pathways in the Major Grass Weed Lolium sp. (Rye-Grass).

PubMed

Duhoux, Arnaud; Pernin, Fanny; Desserre, Diane; Délye, Christophe

2017-01-01

Herbicides are currently pivotal to control weeds and sustain food security. Herbicides must efficiently kill weeds while being as harmless as possible for crops, even crops taxonomically close to weeds. To increase their selectivity toward crops, some herbicides are sprayed in association with safeners that are bioactive compounds exacerbating herbicide-degrading pathways reputedly specifically in crops. However, exacerbated herbicide metabolism is also a key mechanism underlying evolved non-target-site-based resistance to herbicides (NTSR) in weeds. This raised the issue of a possible role of safeners on NTSR evolution in weeds. We investigated a possible effect of the respective field rates of the two broadly used safeners cloquintocet-mexyl and mefenpyr-diethyl on the sensitivity of the troublesome global weed Lolium sp. (rye-grass) to the major herbicides inhibiting acetolactate-synthase (ALS) pyroxsulam and iodosulfuron + mesosulfuron, respectively. Three Lolium sp. populations were studied in three series of experiments. The first experiment series compared the frequencies of plants surviving application of each herbicide alone or in association with its safener. Safener co-application caused a net increase ranging from 5.0 to 46.5% in the frequency of plants surviving the field rate of their associated herbicide. In a second series of experiments, safener effect was assessed on individual plant sensitivity using vegetative propagation. A reduction in sensitivity to pyroxsulam and to iodosulfuron + mesosulfuron was observed for 44.4 and 11.1% of the plants in co-treatment with cloquintocet-mexyl and mefenpyr-diethyl, respectively. A third series of experiments investigated safener effect on the expression level of 19 Lolium sp. NTSR marker genes. Safeners showed an enhancing effect on the expression level of 10 genes. Overall, we demonstrated that cloquintocet-mexyl and mefenpyr-diethyl both reduced the sensitivity of Lolium sp. to their associated ALS-inhibiting herbicide and most likely exacerbated herbicide-degrading secondary metabolism pathways. This suggests that genetic variation for safener response is present in Lolium sp. Thus, a possible, uninvestigated way to NTSR evolution could be selection for increased responsiveness to safener action. Delivering safeners exclusively to the crop could mitigate the risk for NTSR evolution in weeds.

Contrasting patterns of variation in weedy traits and unique crop features in divergent populations of US weedy rice (Oryza sativa sp.) in Arkansas and California.

PubMed

Kanapeckas, Kimberly L; Tseng, Te-Ming; Vigueira, Cynthia C; Ortiz, Aida; Bridges, William C; Burgos, Nilda R; Fischer, Albert J; Lawton-Rauh, Amy

2018-06-01

Weed evolution from crops involves changes in key traits, but it is unclear how genetic and phenotypic variation contribute to weed diversification and productivity. Weedy rice is a conspecific weed of rice (Oryza sativa) worldwide. We used principal component analysis and hierarchical clustering to understand how morphologically and evolutionarily distinct US weedy rice populations persist in rice fields in different locations under contrasting management regimes. Further, we used a representative subset of 15 sequence-tagged site fragments of expressed genes from global Oryza to assess genome-wide sequence variation among populations. Crop hull color and crop-overlapping maturity dates plus awns, seed (panicle) shattering (> 50%), pigmented pericarp and stature variation (30.2% of total phenotypic variance) characterize genetically less diverse California weedy rice. By contrast, wild-like hull color, seed shattering (> 50%) and stature differences (55.8% of total phenotypic variance) typify genetically diverse weedy rice ecotypes in Arkansas. Recent de-domestication of weedy species - such as in California weedy rice - can involve trait combinations indistinguishable from the crop. This underscores the need for strict seed certification with genetic monitoring and proactive field inspection to prevent proliferation of weedy plant types. In established populations, tillage practice may affect weed diversity and persistence over time. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Adaptive nitrogen and integrated weed management in conservation agriculture: impacts on agronomic productivity, greenhouse gas emissions, and herbicide residues.

PubMed

Oyeogbe, Anthony Imoudu; Das, T K; Bhatia, Arti; Singh, Shashi Bala

2017-04-01

Increasing nitrogen (N) immobilization and weed interference in the early phase of implementation of conservation agriculture (CA) affects crop yields. Yet, higher fertilizer and herbicide use to improve productivity influences greenhouse gase emissions and herbicide residues. These tradeoffs precipitated a need for adaptive N and integrated weed management in CA-based maize (Zea mays L.)-wheat [Triticum aestivum (L.) emend Fiori & Paol] cropping system in the Indo-Gangetic Plains (IGP) to optimize N availability and reduce weed proliferation. Adaptive N fertilization was based on soil test value and normalized difference vegetation index measurement (NDVM) by GreenSeeker™ technology, while integrated weed management included brown manuring (Sesbania aculeata L. co-culture, killed at 25 days after sowing), herbicide mixture, and weedy check (control, i.e., without weed management). Results indicated that the 'best-adaptive N rate' (i.e., 50% basal + 25% broadcast at 25 days after sowing + supplementary N guided by NDVM) increased maize and wheat grain yields by 20 and 14% (averaged for 2 years), respectively, compared with whole recommended N applied at sowing. Weed management by brown manuring (during maize) and herbicide mixture (during wheat) resulted in 10 and 21% higher grain yields (averaged for 2 years), respectively, over the weedy check. The NDVM in-season N fertilization and brown manuring affected N 2 O and CO 2 emissions, but resulted in improved carbon storage efficiency, while herbicide residuals in soil were significantly lower in the maize season than in wheat cropping. This study concludes that adaptive N and integrated weed management enhance synergy between agronomic productivity, fertilizer and herbicide efficiency, and greenhouse gas mitigation.

A bioenergy feedstock/vegetable double-cropping system

USDA-ARS?s Scientific Manuscript database

Certain warm-season vegetable crops may lend themselves to bioenergy double-cropping systems, which involve growing a winter annual bioenergy feedstock crop followed by a summer annual crop. The objective of the study was to compare crop productivity and weed communities in different pumpkin product...

Herbicide-resistant crop biotechnology: potential and pitfalls

USDA-ARS?s Scientific Manuscript database

Herbicide-resistant crops are an important agricultural biotechnology that can enable farmers to effectively control weeds without harming their crops. Glyphosate-resistant (i.e. Roundup Ready) crops have been the most commercially successful varieties of herbicide-resistant crops and have been plan...

Carbon supply and storage in tilled and nontilled soils as influenced by cover crops and nitrogen fertilization.

PubMed

Sainju, Upendra M; Singh, Bharat P; Whitehead, Wayne F; Wang, Shirley

2006-01-01

Soil carbon (C) sequestration in tilled and nontilled areas can be influenced by crop management practices due to differences in plant C inputs and their rate of mineralization. We examined the influence of four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], biculture of legume and nonlegume (vetch and rye), and no cover crops (or winter weeds)} and three nitrogen (N) fertilization rates (0, 60 to 65, and 120 to 130 kg N ha(-1)) on C inputs from cover crops, cotton (Gossypium hirsutum L.), and sorghum [Sorghum bicolor (L.) Moench)], and soil organic carbon (SOC) at the 0- to 120-cm depth in tilled and nontilled areas. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic Plinthic Paleudults) from 1999 to 2002 in central Georgia. Total C inputs to the soil from cover crops, cotton, and sorghum from 2000 to 2002 ranged from 6.8 to 22.8 Mg ha(-1). The SOC at 0 to 10 cm fluctuated with C input from October 1999 to November 2002 and was greater from cover crops than from weeds in no-tilled plots. In contrast, SOC values at 10 to 30 cm in no-tilled and at 0 to 60 cm in chisel-tilled plots were greater for biculture than for weeds. As a result, C at 0 to 30 cm was sequestered at rates of 267, 33, -133, and -967 kg C ha(-1) yr(-1) for biculture, rye, vetch, and weeds, respectively, in the no-tilled plot. In strip-tilled and chisel-tilled plots, SOC at 0 to 30 cm decreased at rates of 233 to 1233 kg C ha(-1) yr(-1). The SOC at 0 to 30 cm increased more in cover crops with 120 to 130 kg N ha(-1) yr(-1) than in weeds with 0 kg N ha(-1) yr(-1), regardless of tillage. In the subtropical humid region of the southeastern United States, cover crops and N fertilization can increase the amount of C input and storage in tilled and nontilled soils, and hairy vetch and rye biculture was more effective in sequestering C than monocultures or no cover crop.

Impact of fertilizing pattern on the biodiversity of a weed community and wheat growth.

PubMed

Tang, Leilei; Cheng, Chuanpeng; Wan, Kaiyuan; Li, Ruhai; Wang, Daozhong; Tao, Yong; Pan, Junfeng; Xie, Juan; Chen, Fang

2014-01-01

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds.

INTEGRATED WEED CONTROL IN MAIZE.

PubMed

Latré, J; Dewitte, K; Derycke, V; De Roo, B; Haesaert, G

2015-01-01

Integrated pest management has been implemented as a general practice by EU legislation. As weed control actually is the most important crop protection measure in maize for Western Europe, the new legislation will have its impact. The question is of course which systems can be successfully implemented in practice with respect to labour efficiency and economical parameters. During 3 successive growing seasons (2007, 2008, 2009) weed control in maize was evaluated, the main focus was put on different techniques of integrated weed control and was compared with chemical weed control. Additionally, during 4 successive growing seasons (2011, 2012, 2013 and 2014) two objects based on integrated weed control and two objects based on mechanical weed control were compared to about twenty different objects of conventional chemical weed control. One of the objects based on mechanical weed control consisted of treatment with the flex-tine harrow before and after emergence in combination with chemical weed control at a reduced rate in 3-4 leave stage. The second one consisted of broadcast mechanical treatments before and after emergence followed by a final in-row application of herbicides and an inter-row cultivation at 6-7(8) leave stage. All trials were conducted on the Experimental farm of Bottelare HoGent-UGent on a sandy loam soil. Maize was growing in 1/3 crop rotation. The effect on weed growth as well as the economic impact of the different applications was evaluated. Combining chemical and mechanical weed control is a possible option in conventional farming but the disadvantages must be taken into account. A better planned weed control based on the real present weed-population in combination with a carefully thought-out choice of herbicides should also be considered as an IPM--approach.

Impact of Fertilizing Pattern on the Biodiversity of a Weed Community and Wheat Growth

PubMed Central

Tang, Leilei; Cheng, Chuanpeng; Wan, Kaiyuan; Li, Ruhai; Wang, Daozhong; Tao, Yong; Pan, Junfeng; Xie, Juan; Chen, Fang

2014-01-01

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds. PMID:24416223

Interference and economic threshold level of little seed canary grass in wheat under different sowing times.

PubMed

Hussain, Saddam; Khaliq, Abdul; Matloob, Amar; Fahad, Shah; Tanveer, Asif

2015-01-01

Little seed canary grass (LCG) is a pernicious weed of wheat crop causing enormous yield losses. Information on the interference and economic threshold (ET) level of LCG is of prime significance to rationalize the use of herbicide for its effective management in wheat fields. The present study was conducted to quantify interference and ET density of LCG in mid-sown (20 November) and late-sown (10 December) wheat. Experiment was triplicated in randomized split-plot design with sowing dates as the main plots and LCG densities (10, 20, 30, and 40 plants m(-2)) as the subplots. Plots with two natural infestations of weeds including and excluding LCG were maintained for comparing its interference in pure stands with designated densities. A season-long weed-free treatment was also run. Results indicated that composite stand of weeds, including LCG, and density of 40 LCG plants m(-2) were more competitive with wheat, especially when crop was sown late in season. Maximum weed dry biomass was attained by composite stand of weeds including LCG followed by 40 LCG plants m(-2) under both sowing dates. Significant variations in wheat growth and yield were observed under the influence of different LCG densities as well as sowing dates. Presence of 40 LCG plants m(-2) reduced wheat yield by 28 and 34% in mid- and late-sown wheat crop, respectively. These losses were much greater than those for infestation of all weeds, excluding LCG. Linear regression model was effective in simulating wheat yield losses over a wide range of LCG densities, and the regression equations showed good fit to observed data. The ET levels of LCG were 6-7 and 2.2-3.3 plants m(-2) in mid- and late-sown wheat crop, respectively. Herbicide should be applied in cases when LCG density exceeds these levels under respective sowing dates.

A vacuolar H(+)-pyrophosphatase differential activation and energy coupling integrate the responses of weeds and crops to drought stress.

PubMed

Venancio, Josimara Barcelos; Catunda, Michelle Guedes; Ogliari, Juarez; Rima, Janaína Aparecida Hottz; Okorokova-Facanha, Anna Lvovna; Okorokov, Lev Alexandrovitich; Facanha, Arnoldo Rocha

2014-06-01

Cyperus rotundus L. is a C4 weed of large vegetative and reproductive vigor endowed with competitive advantages over most crop species mainly under adverse environmental conditions. Vacuole functions are critical for the mechanisms of drought resistance, and here the modulation of the primary system of vacuolar ion transport is investigated during a transient water stress imposed to this weed and to C4 crop species (Zea mays L.). The vacuolar H(+) pumps, the H(+)-ATPase and H(+)-PPiase, expression, activities and the energy coupling were spectrophotometrically investigated as key elements in the differential drought-resistance mechanisms developed by weeds and crops. In C. rotundus tonoplasts, ATP hydrolysis was more sensitive to drought than its coupled H(+) transport, which was in turn at least 3-folds faster than that mediated by the H(+)-PPiase. Its PPi hydrolysis was only slightly affected by severe water deficit, contrasting with the disruption induced in the PPi-dependent H(+)-gradient. This effect was antagonized by plant rehydration as the H(+)-PPiase activity was highly stimulated, reassuming a coupled PPi-driven H(+) pumping. Maize tonoplasts exhibited 2-4 times lower hydrolytic activities than that of C. rotundus, but were able to overactivate specifically PPi-dependent H(+) pumping in response to stress relief, resulting in an enhanced H(+)-pumps coupling efficiency. These results together with immunoanalysis revealed profiles consistent with pre- and post-translational changes occurring on the tonoplast H(+)-pumps, which differ between weeds and crops upon water deficit. The evidences highlight an unusual modulation of the H(+)-PPiase energy coupling as a key biochemical change related to environmental stresses adaptive capacity of plants. Copyright © 2014 Elsevier B.V. All rights reserved.

Taxonomic and Life History Bias in Herbicide Resistant Weeds: Implications for Deployment of Resistant Crops

PubMed Central

Holt, Jodie S.; Welles, Shana R.; Silvera, Katia; Heap, Ian M.; Heredia, Sylvia M.; Martinez-Berdeja, Alejandra; Palenscar, Kai T.; Sweet, Lynn C.; Ellstrand, Norman C.

2013-01-01

Evolved herbicide resistance (EHR) is an important agronomic problem and consequently a food security problem, as it jeopardizes herbicide effectiveness and increases the difficulty and cost of weed management. EHR in weeds was first reported in 1970 and the number of cases has accelerated dramatically over the last two decades. Despite 40 years of research on EHR, why some weeds evolve resistance and others do not is poorly understood. Here we ask whether weed species that have EHR are different from weeds in general. Comparing taxonomic and life history traits of weeds with EHR to a control group (“the world's worst weeds”), we found weeds with EHR significantly over-represented in certain plant families and having certain life history biases. In particular, resistance is overrepresented in Amaranthaceae, Brassicaceae and Poaceae relative to all weeds, and annuality is ca. 1.5 times as frequent in weeds with EHR as in the control group. Also, for perennial EHR weeds, vegetative reproduction is only 60% as frequent as in the control group. We found the same trends for subsets of weeds with EHR to acetolactate synthase (ALS), photosystem II (PSII), and 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase-inhibitor herbicides and with multiple resistance. As herbicide resistant crops (transgenic or not) are increasingly deployed in developing countries, the problems of EHR could increase in those countries as it has in the USA if the selecting herbicides are heavily applied and appropriate management strategies are not employed. Given our analysis, we make some predictions about additional species that might evolve resistance. PMID:24039727

International Seed Testing Association List of stabilized plant names, edition 6

USDA-ARS?s Scientific Manuscript database

Seed-testing laboratories determine the quality of seed lots in national and international seed commerce. Those services most commonly requested include purity analysis, noxious-weed seed detection, and viability tests. Rigorous procedures for performing various tests on specific crops have been est...

Using cover crops to alleviate compaction in organic grain farms: effects on weeds and yields

USDA-ARS?s Scientific Manuscript database

Organic producers heavily rely on tillage for mechanical weeding, creating compacted areas ideal for weedy species, and forming a vicious cycle of tillage, compaction and increasing weed populations. In an effort to address the concerns of certified organic farmers from Illinois, we explored the eff...

Implements and cultivation frequency to improve in-row weed control in organic peanut production

USDA-ARS?s Scientific Manuscript database

Weed control in organic peanut production is difficult and costly, which limits expansion of the production system. Sweep cultivation in the row middles is effective, but weeds remain in the crop row causing yield loss. Research trials were conducted in Tifton, GA to evaluate implements and freque...

Factors affecting potential for Palmer amaranth (Amaranthus palmeri) suppression by winter rye in Georgia, USA

USDA-ARS?s Scientific Manuscript database

Herbicide resistant Palmer amaranth (Amaranthus palmeri) has rapidly become a dominant weed management issue in agronomic crops of the Southeast US. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-residue, ro...

Laboratory tests to assess optimal agricultural residue traits for an abrasive weed control system

USDA-ARS?s Scientific Manuscript database

One of the biggest challenges to organic agricultural production and herbicide resistant crops in industrialized countries today is the non-chemical control of weed plants. Studies of new tools and methods for weed control have been motivated by an increased consumer demand for organic produce and c...

Mile-a-minute weed in the northeast

Treesearch

Larry H. McCormick; C. Fagan Johnson

1998-01-01

Mile-a-minute, Polygonum perfoliatum L., is an introduced weed from eastern Asia that is rapidly colonizing non-crop areas in Pennsylvania and surrounding states. Since its introduction into the United States, in south-central Pennsylvania, in the 1930s, the mile-a-minute weed has spread to other regions of Pennsylvania, Delaware, Maryland, New...

Biological control as a tool to mitigate economic impacts of facilitative ecological interactions between the giant reed and cattle fever ticks

USDA-ARS?s Scientific Manuscript database

Annual domestic impacts associated with introduced weeds are conservatively estimated at $27 billion, incorporating costs of weed management, crop losses and displacement of productive rangeland, and displacement of some environmental services. Estimating the total economic damage of invasive weed...

Gibberellic and kaurenoic hybrid strigolactone mimics for seed germination of parasitic weeds.

PubMed

Pereira, Rondinelle G; Cala, Antonio; Fernández-Aparicio, Mónica; Molinillo, José Mg; Boaventura, Maria Ad; Macías, Francisco A

2017-12-01

Parasitic weeds are widespread and cause significant losses in important crops. Their germination requires the detection of crop-derived molecules such as strigolactones. Strigolactone mimics are germination-inducing molecules with the potential to apply a suicidal germination strategy for seed bank control of parasitic weeds. The D-ring, which is instrumental in the germination process of seeds of parasitic weeds, was attached to gibberellin (GA 3 ) and kaurenoic acid as the scaffold. It was shown that indeed strigolactone mimics prepared from GA 3 and kaurenoic acid are active as stimulants when a D-ring is present; some of the mimics are as active as GR24. The starting molecules were plant hormones that had previous growth-regulating activity in other organisms and the products showed enhanced activity towards parasitic weeds. The information generated may contribute to a better understanding of the germination biochemistry of the weed species used. Further research is required in this area but it is clear that the results are promising. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Summer weeds as hosts for Frankliniella occidentalis and Frankliniella fusca (Thysanoptera: Thripidae) and as reservoirs for tomato spotted wilt Tospovirus in North Carolina.

PubMed

Kahn, Noah D; Walgenbach, J F; Kennedy, G G

2005-12-01

In North Carolina, Tomato spotted wilt tospovirus (family Bunyaviridae, genus Tospovirus, TSWV) is vectored primarily by the tobacco thrips, Frankliniella fusca (Hinds), and the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). TSWV overwinters in winter annual weeds from which it is spread to susceptible crops in spring. Because most susceptible crops are destroyed after harvest before winter weeds emerge in the fall, infected summer weeds are thought to be the principal source for spread of TSWV to winter annual weeds in fall. A survey of summer weeds associated with TSWV-susceptible crops in the coastal plain of North Carolina conducted between May and October revealed that relatively few species were commonly infected with TSWV and supported populations of F. fusca or F. occidentalis. F. occidentalis made up > 75% of vector species collected from 15 summer weed species during 2002. The number of F. occidentalis and F. fusca immatures collected from plant samples varied significantly among plant species. Ipomoea purpurea (L.) Roth, Mollugo verticillata L., Cassia obtusifolia L., and Amaranthus palmeri S. Wats supported the largest numbers of immature F. occidentalis. Richardia scabra L., M. verticillata, and Ipomoea hederacea (L.) supported the largest numbers of F. fusca immatures. TSWV was present at 16 of 17 locations, and naturally occurring infections were found in 14 of 29 weed species tested. Five of the TSWV-infected species have not previously been reported as hosts of TSWV (A. palmeri, Solidago altissima L., Ipomoea lacunosa L., I. purpurea, and Phytolacca americana L.). Estimated rates of infection were highest in I. purpurea (6.8%), M. verticillata (5.3%), and I. hederacea (1.9%). When both the incidence of infection by TSWV and the populations of F. occidentalis and F. fusca associated with each weed species are considered, the following summer weed species have the potential to act as significant sources for spread of TSWV to winter annual weeds in fall: I. purpurea, I. hederacea, M. verticillata, A. palmeri, C. obtusifolia, R. scabra, Ambrosia artemisiifolia L., Polygonum pensylvanicum L., and Chenopodium album L.

Elymus repens biomass allocation and acquisition as affected by light and nutrient supply and companion crop competition.

PubMed

Ringselle, Björn; Prieto-Ruiz, Inés; Andersson, Lars; Aronsson, Helena; Bergkvist, Göran

2017-02-01

Competitive crops are a central component of resource-efficient weed control, especially for problematic perennial weeds such as Elymus repens Competition not only reduces total weed biomass, but denial of resources can also change the allocation pattern - potentially away from the underground storage organs that make perennial weeds difficult to control. Thus, the competition mode of crops may be an important component in the design of resource-efficient cropping systems. Our aim was to determine how competition from companion crops with different modes of competition affect E. repens biomass acquisition and allocation and discuss that in relation to how E. repens responds to different levels of light and nutrient supply. Greenhouse experiments were conducted with E. repens growing in interspecific competition with increasing density of perennial ryegrass or red clover, or growing at three levels of both light and nutrient supply. Elymus repens total biomass decreased with increasing biomass of the companion crop and the rate of decrease was higher with red clover than with perennial ryegrass, particularly for E. repens rhizome biomass. A reduced nutrient supply shifted E. repens allocation towards below-ground biomass while a reduced light supply shifted it towards shoot biomass. Red clover caused no change in E. repens allocation pattern, while ryegrass mostly shifted the allocation towards below-ground biomass, but the change was not correlated with ryegrass biomass. The companion crop mode of competition influences both the suppression rate of E. repens biomass acquisition and the likelihood of shifts in E. repens biomass allocation. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effect of crop rotation on soil nutrient balance and weediness in soddy podzolic organic farming fields

NASA Astrophysics Data System (ADS)

Zarina, Livija; Zarina, Liga

2017-04-01

The nutrient balance in different crop rotations under organic cropping system has been investigated in Latvia at the Institute of Agricultural Resources and Economics since 2006. Latvia is located in a humid and moderate climatic region where the rainfall exceeds evaporation (soil moisture coefficient > 1) and the soil moisture regime is characteristic with percolation. The average annual precipitation is 670-850 mm. The average temperature varies from -6.7° C in January to 16.5 °C in July. The growing season is 175 - 185 days. The most widespread are podzolic soils and mainly they are present in agricultural fields in all regions of Latvia. In a wider sense the goal of the soil management in organic farming is a creation of the biologically active flora and fauna in the soil by maintaining a high level of soil organic matter which is good for crops nutrient balance. Crop rotation is a central component of organic farming systems and has many benefits, including growth of soil microbial activity, which may increase nutrient availability. The aim of the present study was to calculate nutrient balance for each crop in the rotations and average in each rotation. Taking into account that crop rotations can limit build-up of weeds, additionally within the ERA-net CORE Organic Plus transnational programs supported project PRODIVA the information required for a better utilization of crop diversification for weed management in North European organic arable cropping systems was summarized. It was found that the nutrient balance was influenced by nutrients uptake by biomass of growing crops in crop rotation. The number of weeds in the organic farming fields with crop rotation is dependent on the cultivated crops and the succession of crops in the crop rotation.

Adaptation to flooding during emergence and seedling growth in rice and weeds, and implications for crop establishment.

PubMed

Ismail, Abdelbagi M; Johnson, David E; Ella, Evangelina S; Vergara, Georgina V; Baltazar, Aurora M

2012-01-01

Direct seeding of rice is being adopted in rainfed and irrigated lowland ecosystems because it reduces labour costs in addition to other benefits. However, early flooding due to uneven fields or rainfall slows down seed germination and hinders crop establishment. Conversely, early flooding helps suppress weeds and reduces the costs of manual weeding and/or dependence on herbicides; however, numerous weed species are adapted to lowlands and present challenges for the use of flooding to control weeds. Advancing knowledge on the mechanisms of tolerance of flooding during germination and early growth in rice and weeds could facilitate the development of improved rice varieties and effective weed management practices for direct-seeded rice. Rice genotypes with a greater ability to germinate and establish in flooded soils were identified, providing opportunities to develop varieties suitable for direct seeding in flooded soils. Tolerance of flooding in these genotypes was mostly attributed to traits associated with better ability to mobilize stored carbohydrates and anaerobic metabolism. Limited studies were undertaken in weeds associated with lowland rice systems. Remaining studies compared rice and weeds and related weed species such as Echinochloa crus-galli and E. colona or compared ecotypes of the same species of Cyperus rotundus adapted to either aerobic or flooded soils. Tolerant weeds and rice genotypes mostly developed similar adaptive traits that allow them to establish in flooded fields, including the ability to germinate and elongate faster under hypoxia, mobilize stored starch reserves and generate energy through fermentation pathways. Remarkably, some weeds developed additional traits such as larger storage tubers that enlarge further in deeper flooded soils (C. rotundus). Unravelling the mechanisms involved in adaptation to flooding will help design management options that will allow tolerant rice genotypes to adequately establish in flooded soils while simultaneously suppressing weeds.

Allelopathic effects of weeds extracts against seed germination of some plants.

PubMed

Kadioglu, Izzet; Yanar, Yusuf; Asav, Unal

2005-04-01

This study investigated the allelopathic effects of various weeds extracts on seed germination of 11 crop species. Most of the weed extracts tested had inhibitory effects on seed germination of common bean, tomato, pepper, squash, onion, barley, wheat, and corn at different application rates as compared with the 10% acetone control. Chickpea seed germination was inhibited by extracts of Solanum nigrum L., Chenopodium album L., and Matricaria chamomilla L. (10%, 20% and 22.5%, respectively) at the end of 21 day incubation period. However, Glycyrrhiza glabra L., Sorghum halepense (L.) Pers., and Reseda lutea L. extracts stimulated chickpea seed germination at the rates of 95%, 94%, and 93%, respectively, compared to control. It was concluded that some of the weed extracts tested in this study could be used as inhibitor while others could be used as stimulator for the crops.

All roads lead to weediness: Patterns of genomic divergence reveal extensive recurrent weedy rice origins from South Asian Oryza.

PubMed

Huang, Zhongyun; Young, Nelson D; Reagon, Michael; Hyma, Katie E; Olsen, Kenneth M; Jia, Yulin; Caicedo, Ana L

2017-06-01

Weedy rice (Oryza spp.), a weedy relative of cultivated rice (O. sativa), infests and persists in cultivated rice fields worldwide. Many weedy rice populations have evolved similar adaptive traits, considered part of the 'agricultural weed syndrome', making this an ideal model to study the genetic basis of parallel evolution. Understanding parallel evolution hinges on accurate knowledge of the genetic background and origins of existing weedy rice groups. Using population structure analyses of South Asian and US weedy rice, we show that weeds in South Asia have highly heterogeneous genetic backgrounds, with ancestry contributions both from cultivated varieties (aus and indica) and wild rice. Moreover, the two main groups of weedy rice in the USA, which are also related to aus and indica cultivars, constitute a separate origin from that of Asian weeds. Weedy rice populations in South Asia largely converge on presence of red pericarps and awns and on ease of shattering. Genomewide divergence scans between weed groups from the USA and South Asia, and their crop relatives are enriched for loci involved in metabolic processes. Some candidate genes related to iconic weedy traits and competitiveness are highly divergent between some weed-crop pairs, but are not shared among all weed-crop comparisons. Our results show that weedy rice is an extreme example of recurrent evolution, and suggest that most populations are evolving their weedy traits through different genetic mechanisms. © 2017 John Wiley & Sons Ltd.

Use of Multicopy Transposons Bearing Unfitness Genes in Weed Control: Four Example Scenarios

PubMed Central

Gressel, Jonathan; Levy, Avraham A.

2014-01-01

We speculate that multicopy transposons, carrying both fitness and unfitness genes, can provide new positive and negative selection options to intractable weed problems. Multicopy transposons rapidly disseminate through populations, appearing in approximately 100% of progeny, unlike nuclear transgenes, which appear in a proportion of segregating populations. Different unfitness transgenes and modes of propagation will be appropriate for different cases: (1) outcrossing Amaranthus spp. (that evolved resistances to major herbicides); (2) Lolium spp., important pasture grasses, yet herbicide-resistant weeds in crops; (3) rice (Oryza sativa), often infested with feral weedy rice, which interbreeds with the crop; and (4) self-compatible sorghum (Sorghum bicolor), which readily crosses with conspecific shattercane and with allotetraploid johnsongrass (Sorghum halepense). The speculated outcome of these scenarios is to generate weed populations that contain the unfitness gene and thus are easily controllable. Unfitness genes can be under chemically or environmentally inducible promoters, activated after gene dissemination, or under constitutive promoters where the gene function is utilized only at special times (e.g. sensitivity to an herbicide). The transposons can be vectored to the weeds by introgression from the crop (in rice, sorghum, and Lolium spp.) or from planted engineered weed (Amaranthus spp.) using a gene conferring the degradation of a no longer widely used herbicide, especially in tandem with an herbicide-resistant gene that kills all nonhybrids, facilitating the rapid dissemination of the multicopy transposons in a weedy population. PMID:24820021

Functional morphology and seed anatomy of the invasive weed, benghal dayflower (Commelina benghalensis): Implications for dispersal by mourning doves

USDA-ARS?s Scientific Manuscript database

Benghal dayflower (BD) is an exotic weed that reduces yields in many agricultural crops. Potential dispersal of this weed by migratory Mourning doves was investigated in this study. Evidence shows that doves feed on BD seeds, with some birds containing hundreds of seeds. Seeds extracted from harvest...

Relative competitive ability of rice with strawhull and blackhull red rice biotypes

USDA-ARS?s Scientific Manuscript database

Weed interference depends largely upon the species composition of the weed community and an ability to compete with the cultured crop. Weedy red rice is a major weed pest of rice in the southern U.S. The focus of this study was to evaluate the competitive ability of rice against common, genetically ...

Weed manipulation for insect pest management in corn

NASA Astrophysics Data System (ADS)

Altieri, M. A.; Whitcomb, W. H.

1980-11-01

Populations of insect pests and associated predaceous arthropods were sampled by direct observation and other relative methods in simple and diversified corn habitats at two sites in north Florida during 1978 and 1979. Through various cultural manipulations, characteristic weed communities were established selectively in alternate rows within corn plots. Fall armyworm ( Spodoptera frugiperda J. E. Smith) incidence was consistently higher in the weed-free habitats than in the corn habitats containing natural weed complexes or selected weed associations. Corn earworm ( Heliothis zea Boddie) damage was similar in all weed-free and weedy treatments, suggesting that this insect is not affected greatly by weed diversity. Only the diversification of corn with a strip of soybean significantly reduced corn earworm damage. In one site, distance between plots was reduced. Because predators moved freely between habitats, it was difficult to identify between-treatment differences in the composition of predator communities. In the other site, increased distances between plots minimized such migrations, resulting in greater population densities and diversity of common foliage insect predators in the weed-manipulated corn systems than in the weed-free plots. Trophic relationships in the weedy habitats were more complex than food webs in monocultures. Predator diversity (measured as mean number of species per area) and predator density was higher in com plots surrounded by mature, complex vegetation than at those surrounded by annual crops. This suggests that diverse adjacent areas to crops provide refuge for predators, thus acting as colonization sources.

Fagopyrum esculentum Alters Its Root Exudation after Amaranthus retroflexus Recognition and Suppresses Weed Growth

PubMed Central

Gfeller, Aurélie; Glauser, Gaétan; Etter, Clément; Signarbieux, Constant; Wirth, Judith

2018-01-01

Weed control by crops through growth suppressive root exudates is a promising alternative to herbicides. Buckwheat (Fagopyrum esculentum) is known for its weed suppression and redroot pigweed (Amaranthus retroflexus) control is probably partly due to allelopathic root exudates. This work studies whether other weeds are also suppressed by buckwheat and if the presence of weeds is necessary to induce growth repression. Buckwheat and different weeds were co-cultivated in soil, separating roots by a mesh allowing to study effects due to diffusion. Buckwheat suppressed growth of pigweed, goosefoot and barnyard grass by 53, 42, and 77% respectively without physical root interactions, probably through allelopathic compounds. Root exudates were obtained from sand cultures of buckwheat (BK), pigweed (P), and a buckwheat/pigweed mixed culture (BK-P). BK-P root exudates inhibited pigweed root growth by 49%. Characterization of root exudates by UHPLC-HRMS and principal component analysis revealed that BK and BK-P had a different metabolic profile suggesting that buckwheat changes its root exudation in the presence of pigweed indicating heterospecific recognition. Among the 15 different markers, which were more abundant in BK-P, tryptophan was identified and four others were tentatively identified. Our findings might contribute to the selection of crops with weed suppressive effects. PMID:29445385

Populations of weedy crop–wild hybrid beets show contrasting variation in mating system and population genetic structure

PubMed Central

Arnaud, Jean-François; Fénart, Stéphane; Cordellier, Mathilde; Cuguen, Joël

2010-01-01

Reproductive traits are key parameters for the evolution of invasiveness in weedy crop–wild hybrids. In Beta vulgaris, cultivated beets hybridize with their wild relatives in the seed production areas, giving rise to crop–wild hybrid weed beets. We investigated the genetic structure, the variation in first-year flowering and the variation in mating system among weed beet populations occurring within sugar beet production fields. No spatial genetic structure was found for first-year populations composed of F1 crop–wild hybrid beets. In contrast, populations composed of backcrossed weed beets emerging from the seed bank showed a strong isolation-by-distance pattern. Whereas gametophytic self-incompatibility prevents selfing in wild beet populations, all studied weed beet populations had a mixed-mating system, plausibly because of the introgression of the crop-derived Sf gene that disrupts self-incompatibility. No significant relationship between outcrossing rate and local weed beet density was found, suggesting no trends for a shift in the mating system because of environmental effects. We further reveal that increased invasiveness of weed beets may stem from positive selection on first-year flowering induction depending on the B gene inherited from the wild. Finally, we discuss the practical and applied consequences of our findings for crop-weed management. PMID:25567926

Fagopyrum esculentum Alters Its Root Exudation after Amaranthus retroflexus Recognition and Suppresses Weed Growth.

PubMed

Gfeller, Aurélie; Glauser, Gaétan; Etter, Clément; Signarbieux, Constant; Wirth, Judith

2018-01-01

Weed control by crops through growth suppressive root exudates is a promising alternative to herbicides. Buckwheat ( Fagopyrum esculentum ) is known for its weed suppression and redroot pigweed ( Amaranthus retroflexus ) control is probably partly due to allelopathic root exudates. This work studies whether other weeds are also suppressed by buckwheat and if the presence of weeds is necessary to induce growth repression. Buckwheat and different weeds were co-cultivated in soil, separating roots by a mesh allowing to study effects due to diffusion. Buckwheat suppressed growth of pigweed, goosefoot and barnyard grass by 53, 42, and 77% respectively without physical root interactions, probably through allelopathic compounds. Root exudates were obtained from sand cultures of buckwheat (BK), pigweed (P), and a buckwheat/pigweed mixed culture (BK-P). BK-P root exudates inhibited pigweed root growth by 49%. Characterization of root exudates by UHPLC-HRMS and principal component analysis revealed that BK and BK-P had a different metabolic profile suggesting that buckwheat changes its root exudation in the presence of pigweed indicating heterospecific recognition. Among the 15 different markers, which were more abundant in BK-P, tryptophan was identified and four others were tentatively identified. Our findings might contribute to the selection of crops with weed suppressive effects.

Establishment of three permanent cover crop seed mixtures in Hungarian vineyards

NASA Astrophysics Data System (ADS)

Miglécz, Tamas; Valkó, Orsolya; Donkó, Ádám; Deák, Balázs; Török, Péter; Kelemen, András; Drexler, Dóra; Tóthmérész, Béla

2015-04-01

In organic vineyard farming sowing high diversity cover crop seed mixtures offers a great opportunity to overcome high-priority problems mitigating vineyard cultivation, such as gain erosion control, save soil fertility, improve soil microbial activity and control weeds. Furthermore, we can also improve the biodiversity and ecosystem services of vineyards. Mainly non-native or low diversity seed mixtures are used for cover cropping containing some grass, grain or Fabaceae species. We studied vegetation development after sowing native high-diversity seed mixtures in four vineyards in an on farm field trial. We compared the effects of 4 treatments: (i) Biocont-Ecowin mixture (12 species), (ii) Fabaceae mixture (9 species), (iii) Grass-forb mixture (16 species) and control (no seed sowing). Study sites were located in Tokaj wine region, East Hungary. Seed mixtures were sown in March, 2012. After sowing, we recorded the percentage cover of vascular plant species in the end of June 2012, 2013 and 2014 in altogether 80 permanent plots. In the first year the establishment and weed control of Biocont-Ecowin and Legume seed mixture was the best. For the second year in inter-rows sown with Grass-herb and Legume seed mixtures we detected decreasing weed cover scores, while in inter-rows sown with Biocont-Ecowin seed mixture and in control inter-rows we detected higher weed cover scores. In the third year we still detected lower weed cover scores in inter-rows sown with Grass-forb and Legume seed mixtures, however on several sites we also detected decreasing cover of sown species. All sown species were detected in our plots during the time of the study, however some species were present only with low cover scores or only in a few plots. Out of the sown species Lotus corniculatus, Medicago lupulina, Plantago lanceolata, Trifolium repens, T. pratense and Coronilla varia established the most successfully, and had high cover scores on most sites even in the second and third year. Our trial to develop species rich cover crops was successful. According to our findings sowing high-diversity seed mixtures in cover cropping offers a good opportunity to gain weed control.

Fusion of pixel and object-based features for weed mapping using unmanned aerial vehicle imagery

NASA Astrophysics Data System (ADS)

Gao, Junfeng; Liao, Wenzhi; Nuyttens, David; Lootens, Peter; Vangeyte, Jürgen; Pižurica, Aleksandra; He, Yong; Pieters, Jan G.

2018-05-01

The developments in the use of unmanned aerial vehicles (UAVs) and advanced imaging sensors provide new opportunities for ultra-high resolution (e.g., less than a 10 cm ground sampling distance (GSD)) crop field monitoring and mapping in precision agriculture applications. In this study, we developed a strategy for inter- and intra-row weed detection in early season maize fields from aerial visual imagery. More specifically, the Hough transform algorithm (HT) was applied to the orthomosaicked images for inter-row weed detection. A semi-automatic Object-Based Image Analysis (OBIA) procedure was developed with Random Forests (RF) combined with feature selection techniques to classify soil, weeds and maize. Furthermore, the two binary weed masks generated from HT and OBIA were fused for accurate binary weed image. The developed RF classifier was evaluated by 5-fold cross validation, and it obtained an overall accuracy of 0.945, and Kappa value of 0.912. Finally, the relationship of detected weeds and their ground truth densities was quantified by a fitted linear model with a coefficient of determination of 0.895 and a root mean square error of 0.026. Besides, the importance of input features was evaluated, and it was found that the ratio of vegetation length and width was the most significant feature for the classification model. Overall, our approach can yield a satisfactory weed map, and we expect that the obtained accurate and timely weed map from UAV imagery will be applicable to realize site-specific weed management (SSWM) in early season crop fields for reducing spraying non-selective herbicides and costs.

Domestic geese: biological weed control in an agricultural setting.

Treesearch

Tricia L. Wurtz

1995-01-01

Vertebrate herbivores can be effective agents of biological weed control in certain applications. I compared the use of domestic geese for weed control in an agricultural field with the herbicide hexazinone and with hand control. Newly planted spruce seedlings acted as a prototype crop that would be unpalatable to the geese. Trampling by geese led to as much as 47%...

Classification of Maize and Weeds by Bayesian Networks

NASA Astrophysics Data System (ADS)

Chapron, Michel; Oprea, Alina; Sultana, Bogdan; Assemat, Louis

2007-11-01

Precision Agriculture is concerned with all sorts of within-field variability, spatially and temporally, that reduces the efficacy of agronomic practices applied in a uniform way all over the field. Because of these sources of heterogeneity, uniform management actions strongly reduce the efficiency of the resource input to the crop (i.e. fertilization, water) or for the agrochemicals use for pest control (i.e. herbicide). Moreover, this low efficacy means high environmental cost (pollution) and reduced economic return for the farmer. Weed plants are one of these sources of variability for the crop, as they occur in patches in the field. Detecting the location, size and internal density of these patches, along with identification of main weed species involved, open the way to a site-specific weed control strategy, where only patches of weeds would receive the appropriate herbicide (type and dose). Herein, an automatic recognition method of vegetal species is described. First, the pixels of soil and vegetation are classified in two classes, then the vegetation part of the input image is segmented from the distance image by using the watershed method and finally the leaves of the vegetation are partitioned in two parts maize and weeds thanks to the two Bayesian networks.

Physiological and Morphological Responses of Ischaemum rugosum Salisb. (Wrinkled Grass) to Different Nitrogen Rates and Rice Seeding Rates

PubMed Central

Awan, Tahir Hussain; Chauhan, Bhagirath Singh; Cruz, Pompe C. Sta.

2014-01-01

Ischaemum rugosum is a competitive weed in direct-seeded rice systems. Developing integrated weed management strategies that promote the suppression of weeds by crop density, cultivar selection, and nutrition requires better understanding of the extent to which rice interferes with the growth of this weed and how it responds to resource limitation due to rice interference. The growth of I. rugosum was studied when grown with four rice seeding rates (0, 25, 50, and 100 kg ha−1) and four nitrogen (N) rates (0, 50, 100, and 150 kg ha−1). Compared to the weed plants grown alone, weed tiller number was reduced by 63–80%, leaf number by 68–77%, leaf area by 69–77%, leaf biomass by 72–84%, and inflorescence biomass by 81–93% at the rice seeding rates of 25–100 kg ha−1. All these parameters increased with increasing rates of N from 0 to 150 kg ha−1. At weed maturity, I. rugosum plants were 100% taller than rice at 0 kg N ha−1, whereas, with added N, the weeds were only 50% taller than rice. Weed biomass increased by 82–160%, whereas rice biomass increased by 92–229%, with the application of 50–150 kg N ha−1. Added N favored rice biomass production more than it did the weed. Rice interference reduced the height and biomass of I. rugosum, but did not suppress its growth completely. I. rugosum showed the ability to reduce the effects of rice interference by increasing leaf area, leaf weight ratio, and specific leaf area, and by decreasing the root-shoot weight ratio in comparison to the weed plants grown alone. The results suggest that rice crop interference alone may reduce I. rugosum growth but may not provide complete control of this weed. The need for integrated weed management practices to effectively control this weed species is highlighted. PMID:24910995

Physiological and morphological responses of Ischaemum rugosum Salisb. (wrinkled grass) to different nitrogen rates and rice seeding rates.

PubMed

Awan, Tahir Hussain; Chauhan, Bhagirath Singh; Cruz, Pompe C Sta

2014-01-01

Ischaemum rugosum is a competitive weed in direct-seeded rice systems. Developing integrated weed management strategies that promote the suppression of weeds by crop density, cultivar selection, and nutrition requires better understanding of the extent to which rice interferes with the growth of this weed and how it responds to resource limitation due to rice interference. The growth of I. rugosum was studied when grown with four rice seeding rates (0, 25, 50, and 100 kg ha(-1)) and four nitrogen (N) rates (0, 50, 100, and 150 kg ha(-1)). Compared to the weed plants grown alone, weed tiller number was reduced by 63-80%, leaf number by 68-77%, leaf area by 69-77%, leaf biomass by 72-84%, and inflorescence biomass by 81-93% at the rice seeding rates of 25-100 kg ha(-1). All these parameters increased with increasing rates of N from 0 to 150 kg ha(-1). At weed maturity, I. rugosum plants were 100% taller than rice at 0 kg N ha(-1), whereas, with added N, the weeds were only 50% taller than rice. Weed biomass increased by 82-160%, whereas rice biomass increased by 92-229%, with the application of 50-150 kg N ha(-1). Added N favored rice biomass production more than it did the weed. Rice interference reduced the height and biomass of I. rugosum, but did not suppress its growth completely. I. rugosum showed the ability to reduce the effects of rice interference by increasing leaf area, leaf weight ratio, and specific leaf area, and by decreasing the root-shoot weight ratio in comparison to the weed plants grown alone. The results suggest that rice crop interference alone may reduce I. rugosum growth but may not provide complete control of this weed. The need for integrated weed management practices to effectively control this weed species is highlighted.

Weed species composition and distribution pattern in the maize crop under the influence of edaphic factors and farming practices: A case study from Mardan, Pakistan.

PubMed

Ahmad, Zeeshan; Khan, Shujaul Mulk; Abd Allah, Elsayed Fathi; Alqarawi, Abdulaziz Abdullah; Hashem, Abeer

2016-11-01

Weeds are unwanted plant species growing in ordinary environment. In nature there are a total of 8000 weed species out of which 250 are important for agriculture world. The present study was carried out on weed species composition and distribution pattern with special reference to edaphic factor and farming practices in maize crop of District Mardan during the months of August and September, 2014. Quadrates methods were used to assess weed species distribution in relation to edaphic factor and farming practices. Phytosociological attributes such as frequency, relative frequency, density, relative density and Importance Values were measured by placing 9 quadrates (1 × 1 m 2 ) randomly in each field. Initial results showed that the study area has 29 diverse weed species belonging to 27 genera and 15 families distributed in 585 quadrats. Presence and absence data sheet of 29 weed species and 65 fields were analyzed through PC-ORD version 5. Cluster and Two Way Cluster Analyses initiated four different weed communities with significant indicator species and with respect to underlying environmental variables using data attribute plots. Canonical Correspondence Analyses (CCA) of CANOCO software version 4.5 was used to assess the environmental gradients of weed species. It is concluded that among all the edaphic factors the strongest variables were higher concentration of potassium, organic matter and sandy nature of soil. CCA plots of both weed species and sampled fields based on questionnaire data concluded the farming practices such as application of fertilizers, irrigation and chemical spray were the main factors in determination of weed communities.

Herbicides as Weed Control Agents: State of the Art: II. Recent Achievements[C

PubMed Central

Kraehmer, Hansjoerg; van Almsick, Andreas; Beffa, Roland; Dietrich, Hansjoerg; Eckes, Peter; Hacker, Erwin; Hain, Ruediger; Strek, Harry John; Stuebler, Hermann; Willms, Lothar

2014-01-01

In response to changing market dynamics, the discovery of new herbicides has declined significantly over the past few decades and has only seen a modest upsurge in recent years. Nevertheless, the few introductions have proven to be interesting and have brought useful innovation to the market. In addition, herbicide-tolerant or herbicide-resistant crop technologies have allowed the use of existing nonselective herbicides to be extended into crops. An increasing and now major challenge is being posed by the inexorable increase in biotypes of weeds that are resistant to herbicides. This problem is now at a level that threatens future agricultural productivity and needs to be better understood. If herbicides are to remain sustainable, then it is a must that we adopt diversity in crop rotation and herbicide use as well as increase the use of nonchemical measures to control weeds. Nevertheless, despite the difficulties posed by resistant weeds and increased regulatory hurdles, new screening tools promise to provide an upsurge of potential herbicide leads. Our industry urgently needs to supply agriculture with new, effective resistance-breaking herbicides along with strategies to sustain their utility. PMID:25104721

Herbicides as weed control agents: state of the art: II. Recent achievements.

PubMed

Kraehmer, Hansjoerg; van Almsick, Andreas; Beffa, Roland; Dietrich, Hansjoerg; Eckes, Peter; Hacker, Erwin; Hain, Ruediger; Strek, Harry John; Stuebler, Hermann; Willms, Lothar

2014-11-01

In response to changing market dynamics, the discovery of new herbicides has declined significantly over the past few decades and has only seen a modest upsurge in recent years. Nevertheless, the few introductions have proven to be interesting and have brought useful innovation to the market. In addition, herbicide-tolerant or herbicide-resistant crop technologies have allowed the use of existing nonselective herbicides to be extended into crops. An increasing and now major challenge is being posed by the inexorable increase in biotypes of weeds that are resistant to herbicides. This problem is now at a level that threatens future agricultural productivity and needs to be better understood. If herbicides are to remain sustainable, then it is a must that we adopt diversity in crop rotation and herbicide use as well as increase the use of nonchemical measures to control weeds. Nevertheless, despite the difficulties posed by resistant weeds and increased regulatory hurdles, new screening tools promise to provide an upsurge of potential herbicide leads. Our industry urgently needs to supply agriculture with new, effective resistance-breaking herbicides along with strategies to sustain their utility. © 2014 American Society of Plant Biologists. All Rights Reserved.

Rye cover crop effects on soil quality in no-till corn silage-soybean cropping systems

USDA-ARS?s Scientific Manuscript database

Corn and soybean farmers in the upper Midwest are showing increasing interest in winter cover crops. Known benefits of winter cover crops include reductions in nutrient leaching, erosion prevention, and weed suppression; however, the effects of winter cover crops on soil quality in this region have ...

Reintroduction of rare arable plants by seed transfer. What are the optimal sowing rates?

PubMed

Lang, Marion; Prestele, Julia; Fischer, Christina; Kollmann, Johannes; Albrecht, Harald

2016-08-01

During the past decades, agro-biodiversity has markedly declined and some species are close to extinction in large parts of Europe. Reintroduction of rare arable plant species in suitable habitats could counteract this negative trend. The study investigates optimal sowing rates of three endangered species (Legousia speculum-veneris (L.) Chaix, Consolida regalis Gray, and Lithospermum arvense L.), in terms of establishment success, seed production, and crop yield losses.A field experiment with partial additive design was performed in an organically managed winter rye stand with study species added in ten sowing rates of 5-10,000 seeds m(-2). They were sown as a single species or as a three-species mixture (pure vs. mixed sowing) and with vs. without removal of spontaneous weeds. Winter rye was sown at a fixed rate of 350 grains m(-2). Performance of the study species was assessed as plant establishment and seed production. Crop response was determined as grain yield.Plant numbers and seed production were significantly affected by the sowing rate, but not by sowing type (pure vs. mixed sowing of the three study species), and weed removal. All rare arable plant species established and reproduced at sowing rates >25 seeds m(-2), with best performance of L. speculum-veneris. Negative density effects occurred to some extent for plant establishment and more markedly for seed production.The impact of the three study species on crop yield followed sigmoidal functions. Depending on the species, a yield loss of 10% occurred at >100 seeds m(-2). Synthesis and applications: The study shows that reintroduction of rare arable plants by seed transfer is a suitable method to establish them on extensively managed fields, for example, in organic farms with low nutrient level and without mechanical weed control. Sowing rates of 100 seeds m(-2) for C. regalis and L. arvense, and 50 seeds m(-2) for L. speculum-veneris are recommended, to achieve successful establishment with negligible crop yield losses.

Adaptation to flooding during emergence and seedling growth in rice and weeds, and implications for crop establishment

PubMed Central

Ismail, Abdelbagi M.; Johnson, David E.; Ella, Evangelina S.; Vergara, Georgina V.; Baltazar, Aurora M.

2012-01-01

Background and aims Direct seeding of rice is being adopted in rainfed and irrigated lowland ecosystems because it reduces labour costs in addition to other benefits. However, early flooding due to uneven fields or rainfall slows down seed germination and hinders crop establishment. Conversely, early flooding helps suppress weeds and reduces the costs of manual weeding and/or dependence on herbicides; however, numerous weed species are adapted to lowlands and present challenges for the use of flooding to control weeds. Advancing knowledge on the mechanisms of tolerance of flooding during germination and early growth in rice and weeds could facilitate the development of improved rice varieties and effective weed management practices for direct-seeded rice. Principal results Rice genotypes with a greater ability to germinate and establish in flooded soils were identified, providing opportunities to develop varieties suitable for direct seeding in flooded soils. Tolerance of flooding in these genotypes was mostly attributed to traits associated with better ability to mobilize stored carbohydrates and anaerobic metabolism. Limited studies were undertaken in weeds associated with lowland rice systems. Remaining studies compared rice and weeds and related weed species such as Echinochloa crus-galli and E. colona or compared ecotypes of the same species of Cyperus rotundus adapted to either aerobic or flooded soils. Conclusions Tolerant weeds and rice genotypes mostly developed similar adaptive traits that allow them to establish in flooded fields, including the ability to germinate and elongate faster under hypoxia, mobilize stored starch reserves and generate energy through fermentation pathways. Remarkably, some weeds developed additional traits such as larger storage tubers that enlarge further in deeper flooded soils (C. rotundus). Unravelling the mechanisms involved in adaptation to flooding will help design management options that will allow tolerant rice genotypes to adequately establish in flooded soils while simultaneously suppressing weeds. PMID:22957137

Increased Productivity of a Cover Crop Mixture Is Not Associated with Enhanced Agroecosystem Services

PubMed Central

Smith, Richard G.; Atwood, Lesley W.; Warren, Nicholas D.

2014-01-01

Cover crops provide a variety of important agroecological services within cropping systems. Typically these crops are grown as monocultures or simple graminoid-legume bicultures; however, ecological theory and empirical evidence suggest that agroecosystem services could be enhanced by growing cover crops in species-rich mixtures. We examined cover crop productivity, weed suppression, stability, and carryover effects to a subsequent cash crop in an experiment involving a five-species annual cover crop mixture and the component species grown as monocultures in SE New Hampshire, USA in 2011 and 2012. The mean land equivalent ratio (LER) for the mixture exceeded 1.0 in both years, indicating that the mixture over-yielded relative to the monocultures. Despite the apparent over-yielding in the mixture, we observed no enhancement in weed suppression, biomass stability, or productivity of a subsequent oat (Avena sativa L.) cash crop when compared to the best monoculture component crop. These data are some of the first to include application of the LER to an analysis of a cover crop mixture and contribute to the growing literature on the agroecological effects of cover crop diversity in cropping systems. PMID:24847902

Rye cover crop effects on soil properties in no-till corn silage/soybean agroecosystems

USDA-ARS?s Scientific Manuscript database

Farmers in the U.S. Corn Belt are showing increasing interest in winter cover crops. Known benefits of winter cover crops include reductions in nutrient leaching, erosion mitigation, and weed suppression, however little research has investigated the effects of winter cover crops on soil properties. ...

Remote sensing to monitor cover crop adoption in southeastern Pennsylvania

USDA-ARS?s Scientific Manuscript database

In the Chesapeake Bay watershed, winter cereal cover crops are often planted in rotation with summer crops to reduce the loss of nutrients and sediment from agricultural systems. Cover crops can also improve soil health, control weeds and pests, supplement forage needs, and support resilient croppin...

Cover crop options and mixes for the upper midwest

USDA-ARS?s Scientific Manuscript database

The implementation of cover crops in Iowa has the potential to decrease soil erosion, weed populations, and the loss of nutrients. Currently, less than 1% of all Iowa farmland is planted to cover crops, most of which is winter rye. This research explores 16 different cover crop treatments planted a...

Influence of cover crops on arthropods, free-living nematodes, and yield in a succeeding no-till soybean crop

USDA-ARS?s Scientific Manuscript database

Production practices that incorporate fall-planted cover crops into no-till agronomic crop rotations have become increasingly popular across the Northeastern United States for weed suppression and enhancing environmental stewardship. Field experiments were conducted in 2011 and 2012 to investigate e...

Certified organic herb mulching demonstration

USDA-ARS?s Scientific Manuscript database

The objective of organo-pestiphytology (the study of organic weed control) is to investigate and develop weed control strategies that are fundamental to the cropping system rather than afterthoughts to a production system. The scarcity of approved organic herbicides reinforces the necessity for org...

Vinegar as a broadcast herbicide for spring-transplanted onions

USDA-ARS?s Scientific Manuscript database

The weed control challenges for onion production are formidable; however, these challenges are even greater for those considering organic crop production. Organic onion producers need additional organic herbicides that can effectively provide post-emergent weed control. Field research was conducted...

Interference of allelopathic rice with paddy weeds at the root level.

PubMed

Yang, X-F; Kong, C-H

2017-07-01

Despite increasing knowledge of the involvement of allelopathy in negative interactions among plants, relatively little is known about its action at the root level. This study aims to enhance understanding of interactions of roots between a crop and associated weeds via allelopathy. Based on a series of experiments with window rhizoboxes and root segregation methods, we examined root placement patterns and root interactions between allelopathic rice and major paddy weeds Cyperus difformis, Echinochloa crus-galli, Eclipta prostrata, Leptochloa chinensis and Oryza sativa (weedy rice). Allelopathic rice inhibited growth of paddy weed roots more than shoots regardless of species. Furthermore, allelopathic rice significantly reduced total root length, total root area, maximum root width and maximum root depth of paddy weeds, while the weeds adjusted horizontal and vertical placement of their roots in response to the presence of allelopathic rice. With the exception of O. sativa (weedy rice), root growth of weeds avoided expanding towards allelopathic rice. Compared with root contact, root segregation significantly increased inhibition of E. crus-galli, E. prostrata and L. chinensis through an increase in rice allelochemicals. In particular, their root exudates induced production of rice allelochemicals. However, similar results were not observed in C. difformis and O. sativa (weedy rice) with either root segregation or root exudate application. The results demonstrate that allelopathic rice interferes with paddy weeds by altering root placement patterns and root interactions. This is the first case of a root behavioural strategy in crop-weed allelopathic interaction. © 2017 German Botanical Society and The Royal Botanical Society of the Netherlands.

Capabilities of unmanned aircraft vehicles for low altitude weed detection

NASA Astrophysics Data System (ADS)

Pflanz, Michael; Nordmeyer, Henning

2014-05-01

Sustainable crop production and food security require a consumer and environmental safe plant protection. It is recently known, that precise weed monitoring approaches could help apply pesticides corresponding to field variability. In this regard the site-specific weed management may contribute to an application of herbicides with higher ecologically aware and economical savings. First attempts of precision agriculture date back to the 1980's. Since that time, remote sensing from satellites or manned aircrafts have been investigated and used in agricultural practice, but are currently inadequate for the separation of weeds in an early growth stage from cultivated plants. In contrast, low-cost image capturing at low altitude from unmanned aircraft vehicles (UAV) provides higher spatial resolution and almost real-time processing. Particularly, rotary-wing aircrafts are suitable for precise path or stationary flight. This minimises motion blur and provides better image overlapping for stitching and mapping procedures. Through improved image analyses and the recent increase in the availability of microcontrollers and powerful batteries for UAVs, it can be expected that the spatial mapping of weeds will be enhanced in the future. A six rotors microcopter was equipped with a modified RGB camera taking images from agricultural fields. The hexacopter operates within predefined pathways at adjusted altitudes (from 5 to 10 m) by using GPS navigation. Different scenarios of optical weed detection have been carried out regarding to variable altitude, image resolution, weed and crop growth stages. Our experiences showed high capabilities for site-specific weed control. Image analyses with regard to recognition of weed patches can be used to adapt herbicide application to varying weed occurrence across a field.

The implications of spatially variable pre‐emergence herbicide efficacy for weed management

PubMed Central

Milne, Alice E; Hull, Richard; Murdoch, Alistair J; Storkey, Jonathan

2017-01-01

Abstract BACKGROUND The efficacy of pre‐emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre‐emergence herbicides, flufenacet and pendimethalin, against Alopecurus myosuroides and investigated the implications of variation in organic matter for weed management using a crop–weed competition model. RESULTS Soil organic matter played a critical role in determining the level of control achieved. The high organic matter soil had more surviving weeds with higher biomass than the low organic matter soil. In the absence of competition, surviving plants recovered to produce the same amount of seed as if no herbicide had been applied. The competition model predicted that weeds surviving pre‐emergence herbicides could compensate for sublethal effects even when competing with the crop. The ED50 (median effective dose) was higher for weed seed production than seedling mortality or biomass. This difference was greatest on high organic matter soil. CONCLUSION These results show that the application rate of herbicides should be adjusted to account for within‐field variation in soil organic matter. The results from the modelling emphasised the importance of crop competition in limiting the capacity of weeds surviving pre‐emergence herbicides to compensate and replenish the seedbank. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:29095563

Ozone exposure of a weed community produces adaptive changes in seed populations of Spergula arvensis.

PubMed

Landesmann, Jennifer B; Gundel, Pedro E; Martínez-Ghersa, M Alejandra; Ghersa, Claudio M

2013-01-01

Tropospheric ozone is one of the major drivers of global change. This stress factor alters plant growth and development. Ozone could act as a selection pressure on species communities composition, but also on population genetic background, thus affecting life history traits. Our objective was to evaluate the consequences of prolonged ozone exposure of a weed community on phenotypic traits of Spergulaarvensis linked to persistence. Specifically, we predicted that the selection pressure exerted by high ozone concentrations as well as the concomitant changes in the weed community would drive population adaptive changes which will be reflected on seed germination, dormancy and longevity. In order to test seed viability and dormancy level, we conducted germination experiments for which we used seeds produced by S. arvensis plants grown within a weed community exposed to three ozone treatments during four years (0, 90 and 120 ppb). We also performed a soil seed bank experiment to test seed longevity with seeds coming from both the four-year ozone exposure experiment and from a short-term treatment conducted at ambient and added ozone concentrations. We found that prolonged ozone exposure produced changes in seed germination, dormancy and longevity, resulting in three S. arvensis populations. Seeds from the 90 ppb ozone selection treatment had the highest level of germination when stored at 75% RH and 25 °C and then scarified. These seeds showed the lowest dormancy level when being subjected to 5 ºC/5% RH and 25 ºC/75% followed by 5% RH storage conditions. Furthermore, ozone exposure increased seed persistence in the soil through a maternal effect. Given that tropospheric ozone is an important pollutant in rural areas, changes in seed traits due to ozone exposure could increase weed persistence in fields, thus affecting weed-crop interactions, which could ultimately reduce crop production.

Ozone Exposure of a Weed Community Produces Adaptive Changes in Seed Populations of Spergula arvensis

PubMed Central

Landesmann, Jennifer B.; Gundel, Pedro E.; Martínez-Ghersa, M. Alejandra; Ghersa, Claudio M.

2013-01-01

Tropospheric ozone is one of the major drivers of global change. This stress factor alters plant growth and development. Ozone could act as a selection pressure on species communities composition, but also on population genetic background, thus affecting life history traits. Our objective was to evaluate the consequences of prolonged ozone exposure of a weed community on phenotypic traits of Spergula arvensis linked to persistence. Specifically, we predicted that the selection pressure exerted by high ozone concentrations as well as the concomitant changes in the weed community would drive population adaptive changes which will be reflected on seed germination, dormancy and longevity. In order to test seed viability and dormancy level, we conducted germination experiments for which we used seeds produced by S. arvensis plants grown within a weed community exposed to three ozone treatments during four years (0, 90 and 120 ppb). We also performed a soil seed bank experiment to test seed longevity with seeds coming from both the four-year ozone exposure experiment and from a short-term treatment conducted at ambient and added ozone concentrations. We found that prolonged ozone exposure produced changes in seed germination, dormancy and longevity, resulting in three S. arvensis populations. Seeds from the 90 ppb ozone selection treatment had the highest level of germination when stored at 75% RH and 25 °C and then scarified. These seeds showed the lowest dormancy level when being subjected to 5 ºC/5% RH and 25 ºC/75% followed by 5% RH storage conditions. Furthermore, ozone exposure increased seed persistence in the soil through a maternal effect. Given that tropospheric ozone is an important pollutant in rural areas, changes in seed traits due to ozone exposure could increase weed persistence in fields, thus affecting weed-crop interactions, which could ultimately reduce crop production. PMID:24086640

Discriminating crop, weeds and soil surface with a terrestrial LIDAR sensor.

PubMed

Andújar, Dionisio; Rueda-Ayala, Victor; Moreno, Hugo; Rosell-Polo, Joan Ramón; Escolá, Alexandre; Valero, Constantino; Gerhards, Roland; Fernández-Quintanilla, César; Dorado, José; Griepentrog, Hans-Werner

2013-10-29

In this study, the evaluation of the accuracy and performance of a light detection and ranging (LIDAR) sensor for vegetation using distance and reflection measurements aiming to detect and discriminate maize plants and weeds from soil surface was done. The study continues a previous work carried out in a maize field in Spain with a LIDAR sensor using exclusively one index, the height profile. The current system uses a combination of the two mentioned indexes. The experiment was carried out in a maize field at growth stage 12-14, at 16 different locations selected to represent the widest possible density of three weeds: Echinochloa crus-galli (L.) P.Beauv., Lamium purpureum L., Galium aparine L.and Veronica persica Poir.. A terrestrial LIDAR sensor was mounted on a tripod pointing to the inter-row area, with its horizontal axis and the field of view pointing vertically downwards to the ground, scanning a vertical plane with the potential presence of vegetation. Immediately after the LIDAR data acquisition (distances and reflection measurements), actual heights of plants were estimated using an appropriate methodology. For that purpose, digital images were taken of each sampled area. Data showed a high correlation between LIDAR measured height and actual plant heights (R2 = 0.75). Binary logistic regression between weed presence/absence and the sensor readings (LIDAR height and reflection values) was used to validate the accuracy of the sensor. This permitted the discrimination of vegetation from the ground with an accuracy of up to 95%. In addition, a Canonical Discrimination Analysis (CDA) was able to discriminate mostly between soil and vegetation and, to a far lesser extent, between crop and weeds. The studied methodology arises as a good system for weed detection, which in combination with other principles, such as vision-based technologies, could improve the efficiency and accuracy of herbicide spraying.

Discriminating Crop, Weeds and Soil Surface with a Terrestrial LIDAR Sensor

PubMed Central

Andújar, Dionisio; Rueda-Ayala, Victor; Moreno, Hugo; Rosell-Polo, Joan Ramón; Escolà, Alexandre; Valero, Constantino; Gerhards, Roland; Fernández-Quintanilla, César; Dorado, José; Griepentrog, Hans-Werner

2013-01-01

In this study, the evaluation of the accuracy and performance of a light detection and ranging (LIDAR) sensor for vegetation using distance and reflection measurements aiming to detect and discriminate maize plants and weeds from soil surface was done. The study continues a previous work carried out in a maize field in Spain with a LIDAR sensor using exclusively one index, the height profile. The current system uses a combination of the two mentioned indexes. The experiment was carried out in a maize field at growth stage 12–14, at 16 different locations selected to represent the widest possible density of three weeds: Echinochloa crus-galli (L.) P.Beauv., Lamium purpureum L., Galium aparine L.and Veronica persica Poir.. A terrestrial LIDAR sensor was mounted on a tripod pointing to the inter-row area, with its horizontal axis and the field of view pointing vertically downwards to the ground, scanning a vertical plane with the potential presence of vegetation. Immediately after the LIDAR data acquisition (distances and reflection measurements), actual heights of plants were estimated using an appropriate methodology. For that purpose, digital images were taken of each sampled area. Data showed a high correlation between LIDAR measured height and actual plant heights (R2 = 0.75). Binary logistic regression between weed presence/absence and the sensor readings (LIDAR height and reflection values) was used to validate the accuracy of the sensor. This permitted the discrimination of vegetation from the ground with an accuracy of up to 95%. In addition, a Canonical Discrimination Analysis (CDA) was able to discriminate mostly between soil and vegetation and, to a far lesser extent, between crop and weeds. The studied methodology arises as a good system for weed detection, which in combination with other principles, such as vision-based technologies, could improve the efficiency and accuracy of herbicide spraying. PMID:24172283

Dicotyledon Weed Quantification Algorithm for Selective Herbicide Application in Maize Crops.

PubMed

Laursen, Morten Stigaard; Jørgensen, Rasmus Nyholm; Midtiby, Henrik Skov; Jensen, Kjeld; Christiansen, Martin Peter; Giselsson, Thomas Mosgaard; Mortensen, Anders Krogh; Jensen, Peter Kryger

2016-11-04

The stricter legislation within the European Union for the regulation of herbicides that are prone to leaching causes a greater economic burden on the agricultural industry through taxation. Owing to the increased economic burden, research in reducing herbicide usage has been prompted. High-resolution images from digital cameras support the studying of plant characteristics. These images can also be utilized to analyze shape and texture characteristics for weed identification. Instead of detecting weed patches, weed density can be estimated at a sub-patch level, through which even the identification of a single plant is possible. The aim of this study is to adapt the monocot and dicot coverage ratio vision (MoDiCoVi) algorithm to estimate dicotyledon leaf cover, perform grid spraying in real time, and present initial results in terms of potential herbicide savings in maize. The authors designed and executed an automated, large-scale field trial supported by the Armadillo autonomous tool carrier robot. The field trial consisted of 299 maize plots. Half of the plots (parcels) were planned with additional seeded weeds; the other half were planned with naturally occurring weeds. The in-situ evaluation showed that, compared to conventional broadcast spraying, the proposed method can reduce herbicide usage by 65% without measurable loss in biological effect.

Dicotyledon Weed Quantification Algorithm for Selective Herbicide Application in Maize Crops

PubMed Central

Laursen, Morten Stigaard; Jørgensen, Rasmus Nyholm; Midtiby, Henrik Skov; Jensen, Kjeld; Christiansen, Martin Peter; Giselsson, Thomas Mosgaard; Mortensen, Anders Krogh; Jensen, Peter Kryger

2016-01-01

The stricter legislation within the European Union for the regulation of herbicides that are prone to leaching causes a greater economic burden on the agricultural industry through taxation. Owing to the increased economic burden, research in reducing herbicide usage has been prompted. High-resolution images from digital cameras support the studying of plant characteristics. These images can also be utilized to analyze shape and texture characteristics for weed identification. Instead of detecting weed patches, weed density can be estimated at a sub-patch level, through which even the identification of a single plant is possible. The aim of this study is to adapt the monocot and dicot coverage ratio vision (MoDiCoVi) algorithm to estimate dicotyledon leaf cover, perform grid spraying in real time, and present initial results in terms of potential herbicide savings in maize. The authors designed and executed an automated, large-scale field trial supported by the Armadillo autonomous tool carrier robot. The field trial consisted of 299 maize plots. Half of the plots (parcels) were planned with additional seeded weeds; the other half were planned with naturally occurring weeds. The in-situ evaluation showed that, compared to conventional broadcast spraying, the proposed method can reduce herbicide usage by 65% without measurable loss in biological effect. PMID:27827908

Robust crop and weed segmentation under uncontrolled outdoor illumination

USDA-ARS?s Scientific Manuscript database

A new machine vision for weed detection was developed from RGB color model images. Processes included in the algorithm for the detection were excessive green conversion, threshold value computation by statistical analysis, adaptive image segmentation by adjusting the threshold value, median filter, ...

Signatures of adaptation in the weedy rice genome.

PubMed

Li, Lin-Feng; Li, Ya-Ling; Jia, Yulin; Caicedo, Ana L; Olsen, Kenneth M

2017-05-01

Crop domestication provided the calories that fueled the rise of civilization. For many crop species, domestication was accompanied by the evolution of weedy crop relatives, which aggressively outcompete crops and reduce harvests. Understanding the genetic mechanisms that underlie the evolution of weedy crop relatives is critical for agricultural weed management and food security. Here we use whole-genome sequences to examine the origin and adaptation of the two major strains of weedy rice found in the United States. We find that de-domestication from cultivated ancestors has had a major role in their evolution, with relatively few genetic changes required for the emergence of weediness traits. Weed strains likely evolved both early and late in the history of rice cultivation and represent an under-recognized component of the domestication process. Genomic regions identified here that show evidence of selection can be considered candidates for future genetic and functional analyses for rice improvement.

Can herbicide safeners allow selective control of weedy rice infesting rice crops?

PubMed

Busi, Roberto; Nguyen, Nghia K; Chauhan, Bhagirath S; Vidotto, Francesco; Tabacchi, Maurizio; Powles, Stephen B

2017-01-01

Rice is a major field crop of paramount importance for global food security. However, the increased adoption of more profitable and resource-efficient direct-seeded rice (DSR) systems has contributed to greater weed infestations, including weedy rice, which has become a severe problem in several Asian regions. In this study we have developed a conceptually novel method to protect rice plants at high doses of clomazone and triallate. The insecticide phorate applied to rice seeds provided a substantial level of protection against the herbicides clomazone or triallate. A quantity of 15 kg phorate ha -1 significantly increased the LD 50 values, which were more than twofold greater than for rice plants treated only with clomazone. A quantity of 20 kg phorate ha -1 in combination with 2000 g triallate ha -1 safened rice plants (80% survival) with LD 50 >3.4-fold greater than in phorate-untreated rice. Weed control efficacy was not lowered by the presence of phorate-treated rice seeds. Weedy rice is one of the most damaging global weeds and a major threat to DSR systems. In this study we have developed a proof-of-concept method to allow selective weedy rice control in rice crops. We call for herbicide discovery programmes and research to identify candidate safener and herbicide combinations to achieve selective herbicide control of weedy rice and alleviate weed infestations in global rice crops. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Call of the wild rice: Oryza rufipogon shapes weedy rice evolution in Southeast Asia

USDA-ARS?s Scientific Manuscript database

Agricultural weeds serve as models for studying the genetic basis of rapid adaptation, with weed-adaptive traits potentially evolving independently in geographically distinct but environmentally similar agroecosystems. Weedy relatives of domesticated crops can be especially interesting systems becau...

Weed control in conservation agriculture

USDA-ARS?s Scientific Manuscript database

Prior to the introduction of the selective herbicide, 2,4-D (2,4-dichlorophenoxyacetic acid), in the 1940’s, weed control in agricultural crops was primarily achieved through mechanical cultivation of the soil. Since that time, an increasing number of highly efficacious herbicide options, paired wi...

Organic weed control in certified organic watermelon production

USDA-ARS?s Scientific Manuscript database

The increasing perception by consumers that organic food tastes better and is healthier continues to expand the demand for organically produced crops. Field research was conducted in southeast Oklahoma to determine the impact of organic production systems on weed control and watermelon (Citrullus l...

Glyphosate degradation in glyphosate-resistant and -susceptible crops and weeds.

PubMed

Duke, Stephen O

2011-06-08

High levels of aminomethylphosphonic acid (AMPA), the main glyphosate metabolite, have been found in glyphosate-treated, glyphosate-resistant (GR) soybean, apparently due to plant glyphosate oxidoreductase (GOX)-like activity. AMPA is mildly phytotoxic, and under some conditions the AMPA accumulating in GR soybean correlates with glyphosate-caused phytotoxicity. A bacterial GOX is used in GR canola, and an altered bacterial glyphosate N-acetyltransferase is planned for a new generation of GR crops. In some weed species, glyphosate degradation could contribute to natural resistance. Neither an isolated plant GOX enzyme nor a gene for it has yet been reported in plants. Gene mutation or amplification of plant genes for GOX-like enzyme activity or horizontal transfer of microbial genes from glyphosate-degrading enzymes could produce GR weeds. Yet, there is no evidence that metabolic degradation plays a significant role in evolved resistance to glyphosate. This is unexpected, considering the extreme selection pressure for evolution of glyphosate resistance in weeds and the difficulty in plants of evolving glyphosate resistance via other mechanisms.

Forward selection for multiple resistance across the non-selective glyphosate, glufosinate and oxyfluorfen herbicides in Lolium weed species.

PubMed

Fernández, Pablo; Alcántara, Ricardo; Osuna, María D; Vila-Aiub, Martin M; Prado, Rafael De

2017-05-01

In the Mediterranean area, Lolium species have evolved resistance to glyphosate after decades of continual use without other alternative chemicals in perennial crops (olive, citrus and vineyards). In recent years, oxyfluorfen alone or mixed with glyphosate and glufosinate has been introduced as a chemical option to control dicot and grass weeds. Dose-response studies confirmed that three glyphosate-resistant Lolium weed species (L. rigidum, L. perenne, L. multiflorum) collected from perennial crops in the Iberian Peninsula have also evolved resistance to glufosinate and oxyfluorfen herbicides, despite their recent introduction. Based on the LD 50 resistance parameter, the resistance factor was similar among Lolium species and ranged from 14- to 21-fold and from ten- to 12-fold for oxyfluorfen and glufosinate respectively. Similarly, about 14-fold resistance to both oxyfluorfen and glufosinate was estimated on average for the three Lolium species when growth reduction (GR 50 ) was assessed. This study identified oxyfluorfen resistance in a grass species for the first time. A major threat to sustainability of perennial crops in the Iberian Peninsula is evident, as multiple resistance to non-selective glyphosate, glufosinate and oxyfluorfen herbicides has evolved in L. rigidum, L. perenne and L. multiflorum weeds. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Oilseed cuphea tolerates bromoxynil

USDA-ARS?s Scientific Manuscript database

Weed management is a critical feature of all crop production, but especially for new and alternative crops with which most growers have little experience. Oilseed cuphea is a new annual crop for temperate regions and, at present, it is known to tolerate only a narrow spectrum of herbicides. Addition...

Effect of long-term fertilisation on the weed community of a winter wheat field.

PubMed

Jiang, Min; Liu, Tao; Huang, Niansheng; Shen, Xinping; Shen, Mingxing; Dai, Qigen

2018-03-05

Effects of fertilisation and other management techniques on a weed community were evaluated during wheat growth in a rice-wheat cropping system. Fertiliser treatments were C0 (C means chemical, C0 means zero chemical fertiliser.), CN (N fertiliser), CNK (N plus K fertiliser), CNPK (N plus P and K fertiliser), CNP (N plus P fertiliser), and CPK (P plus K fertiliser). Weed density, biomass, and bio-diversity were determined. Redundancy analysis (RDA) was used to investigate the relationship between fertiliser management, weed species, and weed density. The overall weed densities in the C0 and CPK treatments were the greatest during wheat seeding and ripening periods and were significantly greater than densities in the other treatments. N, P and organic matter in soil were highly correlated with weed species and density, whereas K in soil was not significantly correlated with weed species and weed density. N fertiliser significantly reduced weed density. Balanced fertilisation maintained weed species richness and resulting in a high yield of wheat. CNPK application reduced weed damage and improved the productivity and stability of the farmland ecosystem.

Effects on weed and invertebrate abundance and diversity of herbicide management in genetically modified herbicide-tolerant winter-sown oilseed rape

PubMed Central

Bohan, David A; Boffey, Caroline W.H; Brooks, David R; Clark, Suzanne J; Dewar, Alan M; Firbank, Les G; Haughton, Alison J; Hawes, Cathy; Heard, Matthew S; May, Mike J; Osborne, Juliet L; Perry, Joe N; Rothery, Peter; Roy, David B; Scott, Rod J; Squire, Geoff R; Woiwod, Ian P; Champion, Gillian T

2005-01-01

We evaluated the effects of the herbicide management associated with genetically modified herbicide-tolerant (GMHT) winter oilseed rape (WOSR) on weed and invertebrate abundance and diversity by testing the null hypothesis that there is no difference between the effects of herbicide management of GMHT WOSR and that of comparable conventional varieties. For total weeds there were few treatment differences between GMHT and conventional cropping, but large and opposite treatment effects were observed for dicots and monocots. In the GMHT treatment, there were fewer dicots and more monocots than in conventional crops. At harvest, dicot biomass and seed rain in the GMHT treatment were one-third of that in the conventional, while monocot biomass was threefold greater and monocot seed rain almost fivefold greater in the GMHT treatment than in the conventional. These differential effects persisted into the following two years of the rotation. Bees and butterflies that forage and select for dicot weeds were less abundant in GMHT WOSR management in July. Year totals for Collembola were greater under GMHT management. There were few other treatment effects on invertebrates, despite the marked effects of herbicide management on the weeds. PMID:15799941

Effects on weed and invertebrate abundance and diversity of herbicide management in genetically modified herbicide-tolerant winter-sown oilseed rape.

PubMed

Bohan, David A; Boffey, Caroline W H; Brooks, David R; Clark, Suzanne J; Dewar, Alan M; Firbank, Les G; Haughton, Alison J; Hawes, Cathy; Heard, Matthew S; May, Mike J; Osborne, Juliet L; Perry, Joe N; Rothery, Peter; Roy, David B; Scott, Rod J; Squire, Geoff R; Woiwod, Ian P; Champion, Gillian T

2005-03-07

We evaluated the effects of the herbicide management associated with genetically modified herbicide-tolerant (GMHT) winter oilseed rape (WOSR) on weed and invertebrate abundance and diversity by testing the null hypotheses that there is no difference between the effects of herbicide management of GMHT WOSR and that of comparable conventional varieties. For total weeds, there were few treatment differences between GMHT and conventional cropping, but large and opposite treatment effects were observed for dicots and monocots. In the GMHT treatment, there were fewer dicots and monocots than in conventional crops. At harvest, dicot biomass and seed rain in the GMHT treatment were one-third of that in the conventional, while monocot biomass was threefold greater and monocot seed rain almost fivefold greater in the GMHT treatment than in the conventional. These differential effects persisted into the following two years of the rotation. Bees and Butterflies that forage and select for dicot weeds were less abundant in GMHT WORS management in July. Year totals for Collembola were greater under GMHT management. There were few other treatment effects on invertebrates, despite the marked effects of herbicide management on the weeds.

Herbicidal activity of slow-release herbicide formulations in wheat stands infested by weeds.

PubMed

Zhila, Natalia; Murueva, Anastasiya; Shershneva, Anna; Shishatskaya, Ekaterina; Volova, Tatiana

2017-10-03

The present study reports the herbicidal activity of metribuzin and tribenuron-methyl embedded in the degradable matrix of natural poly-3-hydroxybutyrate [P(3HB)/MET and P(3HB)/TBM]. The developed formulations were constructed as films and microgranules, which were tested against the weeds such as white sweet clover Melilotus albus and lamb's quarters Chenopodium album in the presence of soft spring wheat (Triticum aestivum, cv. Altaiskaya 70) as the subject crop for investigation. The activity was measured in laboratory scale experiments by determining the density and weight of the vegetative organs of weeds. The study was also aimed at testing the effect of the experimental formulation on the growth of wheat crop as dependent on the method of herbicide delivery. The experimental MET and TBM formulations showed pronounced herbicidal activity against the weed species used in the study. The effectiveness of the experimental formulations in inhibiting weed growth was comparable to and, sometimes, higher than that of the commercial formulations (positive control). The amount of the biomass of the wheat treated with the experimental herbicide formulations was significantly greater than that of the wheat treated with commercial formulations.

Sugarcane field residue and root allelopathic impact on weed seed germination

USDA-ARS?s Scientific Manuscript database

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, which can include compounds released from a crop that adversely impact weed species. The objective of this research was to determine the allelopathic impact of sugarcane (Saccharum off...

Dissipation and transport of clopyralid in soil: Effect of application strategies

USDA-ARS?s Scientific Manuscript database

At present there are no herbicides registered for broadleaf weed control in buckwheat. Clopyralid, mixed with desmedipham, was anticipated to provide early-season broadleaf weed suppression with minimal crop injury. However, field trials resulted in limited success which brought to question the fate...

Post-directed application of a potential organic herbicide for bell peppers

USDA-ARS?s Scientific Manuscript database

Organic pepper (Capsicum annuum L.) producers need appropriate herbicides that can effectively provide post-emergent weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of a potential organic herbicide on weed control efficacy, crop injury, an...

Agricultural residues are efficient abrasive tools for weed control

USDA-ARS?s Scientific Manuscript database

Non-chemical control of weeds is one of the most important needs of organic agricultural production and, ironically, herbicide resistant crops. There is a knowledge gap regarding alternative control methods that reduce the use of herbicides. This need for alternatives is motivated by increased consu...

Windrow burning eliminates Italian Ryegrass (Lolium perenne ssp. multiflorum) seed viability

USDA-ARS?s Scientific Manuscript database

Burning of crop residues that have been concentrated behind the harvest combine (windrowed) is one of several harvest weed seed control strategies that have been developed and evaluated in Australia to address the widespread evolution of multiple herbicide resistance in annual weeds. Herbicide-resis...

A specialist-generalist classification of the arable flora and its response to changes in agricultural practices

PubMed Central

2010-01-01

Background Theory in ecology points out the potential link between the degree of specialisation of organisms and their responses to disturbances and suggests that this could be a key element for understanding the assembly of communities. We evaluated this question for the arable weed flora as this group has scarcely been the focus of ecological studies so far and because weeds are restricted to habitats characterised by very high degrees of disturbance. As such, weeds offer a case study to ask how specialization relates to abundance and distribution of species in relation to the varying disturbance regimes occurring in arable crops. Results We used data derived from an extensive national monitoring network of approximately 700 arable fields scattered across France to quantify the degree of specialisation of 152 weed species using six different ecological methods. We then explored the impact of the level of disturbance occurring in arable fields by comparing the degree of specialisation of weed communities in contrasting field situations. The classification of species as specialist or generalist was consistent between different ecological indices. When applied on a large-scale data set across France, this classification highlighted that monoculture harbour significantly more specialists than crop rotations, suggesting that crop rotation increases abundance of generalist species rather than sets of species that are each specialised to the individual crop types grown in the rotation. Applied to a diachronic dataset, the classification also shows that the proportion of specialist weed species has significantly decreased in cultivated fields over the last 30 years which suggests a biotic homogenization of agricultural landscapes. Conclusions This study shows that the concept of generalist/specialist species is particularly relevant to understand the effect of anthropogenic disturbances on the evolution of plant community composition and that ecological theories developed in stable environments are valid in highly disturbed environments such as agro-ecosystems. The approach developed here to classify arable weeds according to the breadth of their ecological niche is robust and applicable to a wide range of organisms. It is also sensitive to disturbance regime and we show here that recent changes in agricultural practices, i.e. increased levels of disturbance have favoured the most generalist species, hence leading to biotic homogenisation in arable landscapes. PMID:20809982

Honey bee diet in intensive farmland habitats reveals an unexpectedly high flower richness and a major role of weeds.

PubMed

Requier, Fabrice; Odoux, Jean-François; Tamic, Thierry; Moreau, Nathalie; Henry, Mickaël; Decourtye, Axel; Bretagnolle, Vincent

2015-06-01

In intensive farmland habitats, pollination of wild flowers and crops may be threatened by the widespread decline of pollinators. The honey bee decline, in particular, appears to result from the combination of multiple stresses, including diseases, pathogens, and pesticides. The reduction of semi-natural habitats is also suspected to entail floral resource scarcity for bees. Yet, the seasonal dynamics and composition of the honey bee diet remains poorly documented to date. In this study, we studied the seasonal contribution of mass-flowering crops (rapeseed and sunflower) vs. other floral resources, as well as the influence of nutritional quality and landscape composition on pollen diet composition over five consecutive years. From April to October, the mass of pollen and nectar collected by honey bees followed a bimodal seasonal trend, marked by a two-month period of low food supply between the two oilseed crop mass-flowerings (ending in May for rapeseed and July for sunflower). Bees collected nectar mainly from crops while pollen came from a wide diversity of herbaceous and woody plant species in semi-natural habitats or from weeds in crops. Weed species constituted the bulk of the honey bee diet between the mass flowering crop periods (up to 40%) and are therefore suspected to play a critical role at this time period. The pollen diet composition was related to the nutritional value of the collected pollen and by the local landscape composition. Our study highlights (1) a food supply depletion period of both pollen and nectar resources during late spring, contemporaneously with the demographic peak of honey bee populations, (2) a high botanical richness of pollen diet, mostly proceeding from trees and weeds, and (3) a pollen diet composition influenced by the local landscape composition. Our results therefore support the Agri-Environmental Schemes intended to promote honey bees and beekeeping sustainability through the enhancement of flower availability in agricultural landscapes.

Push-Pull: Chemical Ecology-Based Integrated Pest Management Technology.

PubMed

Khan, Zeyaur; Midega, Charles A O; Hooper, Antony; Pickett, John

2016-07-01

Lepidopterous stemborers, and parasitic striga weeds belonging to the family Orobanchaceae, attack cereal crops in sub-Saharan Africa causing severe yield losses. The smallholder farmers are resource constrained and unable to afford expensive chemicals for crop protection. The push-pull technology, a chemical ecology- based cropping system, is developed for integrated pest and weed management in cereal-livestock farming systems. Appropriate plants were selected that naturally emit signaling chemicals (semiochemicals). Plants highly attractive for stemborer egg laying were selected and employed as trap crops (pull), to draw pests away from the main crop. Plants that repelled stemborer females were selected as intercrops (push). The stemborers are attracted to the trap plant, and are repelled from the main cereal crop using a repellent intercrop (push). Root exudates of leguminous repellent intercrops also effectively control the parasitic striga weed through an allelopathic mechanism. Their root exudates contain flavonoid compounds some of which stimulate germination of Striga hermonthica seeds, such as Uncinanone B, and others that dramatically inhibit their attachment to host roots, such as Uncinanone C and a number of di-C-glycosylflavones (di-CGFs), resulting in suicidal germination. The intercrop also improves soil fertility through nitrogen fixation, natural mulching, improved biomass, and control of erosion. Both companion plants provide high value animal fodder, facilitating milk production and diversifying farmers' income sources. The technology is appropriate to smallholder mixed cropping systems in Africa. Adopted by about 125,000 farmers to date in eastern Africa, it effectively addresses major production constraints, significantly increases maize yields, and is economical as it is based on locally available plants, not expensive external inputs.

Crop diversification, tillage, and management system influences on spring wheat yield and soil water use

USDA-ARS?s Scientific Manuscript database

Depleted soil quality, decreased water availability, and increased weed competition constrain spring wheat production in the northern Great Plains. Integrated crop management systems are necessary for improved crop productivity. We conducted a field experiment from 2004-2010 comparing productivity...

Herbicide and cover crop residue integration in conservation tillage tomato

USDA-ARS?s Scientific Manuscript database

The increased adoption of conservation tillage in vegetable production requires more information on the role of various cover crops in weed control, tomato quality, and yield. Three conservation-tillage systems utilizing crimson clover, turnip, and cereal rye as winter cover crops were compared to a...

Evaluation of Learning Group Approaches for Fostering Integrated Cropping Systems Management

ERIC Educational Resources Information Center

Blissett, Hana; Simmons, Steve; Jordan, Nicholas; Nelson, Kristen

2004-01-01

Cropping systems management requires integration of multiple forms of knowledge, practice, and learning by farmers, extension educators, and researchers. We evaluated the outcomes of participation in collaborative learning groups organized to address cropping systems and, specifically, challenges of integrated weed management. Groups were…

Potential organic herbicides for squash production: Pelargonic acid herbicides AXXE (registered trademark) and Scythe (registered trademark)

USDA-ARS?s Scientific Manuscript database

Organic squash (Cucurbita pepo L.) producers need appropriate herbicides that can effectively provide season- long weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of potential organic herbicides on weed control efficacy, crop injury, and y...

Parboiled rice hull mulch in containers reduces liverwort and bittercress growth

USDA-ARS?s Scientific Manuscript database

Use of preemergence herbicides for weed control is not always possible; some crops and many enclosed production sites are not labeled for herbicide applications. The objective of this research was to determine the utility of parboiled rice hull mulch for controlling two of the most common weeds in ...

Detection of Papaya ringspot virus type W infecting the cucurbit weed Cucumis melo var. dudaim in Florida

USDA-ARS?s Scientific Manuscript database

This is the first report of Papaya ringspot virus type W infecting Cucumis melo var. dudaim, a cucurbit weed, in Florida. It provides an overview of this virus reservoir for growers, extension workers, crop consultants and research and regulatory scientists....

Evaluation of herbicide efficacy, injury and yield in white lupin (Lupinus albus L.)

USDA-ARS?s Scientific Manuscript database

White lupin is of increasing interest in the southeastern USA as a winter legume cover crop or as mid-winter forage for ruminants. White lupins are poor weed competitors during early establishment which makes effective weed control necessary, however, only three herbicides are currently registered f...

Integrating sheep grazing into cereal-based crop rotations: spring wheat yields and weed communities

USDA-ARS?s Scientific Manuscript database

Crop diversification and integration of livestock into cropping systems may improve the economic and environmental sustainability of agricultural systems. However, few studies have examined the integration of these practices in the semiarid areas of the Northern Great Plains (NGP). A 3-yr experiment...

Using fitness parameters to evaluate three oilseed Brassicaceae species as potential oil crops in two contrasting environments

USDA-ARS?s Scientific Manuscript database

Thlaspi arvense and Camelina sativa have gained considerable attention as biofuel crops. But in some areas, these species, including C. microcarpa, are becoming rare weeds because of agriculture intensification. Including them as crops could guarantee their conservation in agricultural systems. The ...

A comparison of drill and broadcast methods for establishing cover crops on beds

USDA-ARS?s Scientific Manuscript database

Cover crops stands that are sufficiently dense soon after planting are more likely to suppress weeds, scavenge nutrients, and reduce erosion. Small-scale organic vegetable farmers often use broadcasting methods to establish cover crops but lack information on the most effective tool to incorporate ...

The effects of mulching, tillage, and herbicides on weed control and watermelon yield

USDA-ARS?s Scientific Manuscript database

Currently few producers in the Southeast US have adopted conservation tillage practices in specialty crop production. The lack of conservation adoption is likely due to the added challenges in producing vegetables in cover crop residues, especially high biomass cover crop systems. The objective of t...

Ecological and agriculture impacts of bakery yeast wastewater use on weed communities and crops in an arid environment.

PubMed

Abu-Dieyeh, Mohammed H; Diab, Mahmoud; Al-Ghouti, Mohammad A

2017-06-01

The goal of this study was to evaluate the impact of using yeast wastewater (YW) on weed communities. The study showed that all ecological parameters including species richness, dispersion, density, frequency, and % of vegetation cover were significantly increased in the site irrigated with YW compared to a natural rain fed site and another site irrigated with fresh water. The vegetation cover (%) was significantly increased by 2-folds in the site irrigated with YW (52%) than the one irrigated with fresh water (27%). Species richness increases to 23 in the site irrigated with yeast wastewater compared to 12 species in natural rain fed site and 7 species in areas irrigated with fresh water. The 10 studied weed species germinated better at 10 and 20% dilutions of baker's YW. However, only five species achieved few germination (3-25%) at 50% of YW and the two species Sisymbrim irio and Cardariia droba achieved (6-13%) germination using 100% YW. No germination occurred for the crop seeds (tomato, squash, lentil, and barley) at 50 and 100% YW. For tomato, 10 and 20% of YW achieved better germination (82 and 63%, respectively) than the seeds of other species, followed by barley with 80 and 53% of germination. Squash showed the lowest germination percentage with 59 and 42% at 10 and 20% of YW, respectively. Yeast wastewater seems to be crop specific and can affect weed species composition and relative abundances and care should be taken before using the effluent for irrigation of tree plantations and crops.

Growth analysis and yield of two varieties of groundnut (Arachis hypogaea L.) as influenced by different weed control methods.

PubMed

Olayinka, Bolaji U; Etejere, Emmanuel O

Field trials were carried out to evaluate the effects of seven weed management strategies on the growth and yield of two groundnut varieties (Samnut 10 and MK 373) for two successive seasons (2010-2011). The experimental layout was a split plot complete randomized block design with three replications. The two groundnut varieties showed identical pattern of results for leaf area index, dry matter accumulation, relative growth rate, net assimilation rate and crop growth rate as well as yield. All the weed control treatments significantly enhanced the growth and yield compared with the weedy check. The weed free check had the highest growth but the highest yield was recorded from rice straw mulch at 0.1 m depth + one hand weeding at 6 weeks after sowing (WAS) due to increase in number of matured pods per plant, seed weight per plant and 100-seed weight. The results showed that rice straw mulch at 0.1 m depth + one hand weeding at 6 WAS was better agronomical practice for enhancing growth and yield of groundnut. This enhancement could be as a result of its positive influence on physiological parameters such as leaf area index, dry matter accumulation, relative growth rate, net assimilation rate and crop growth rate. Its use is also ecofriendly as it limits the need for synthetic herbicide.

Cross-resistance to prosulfocarb + S-metolachlor and pyroxasulfone selected by either herbicide in Lolium rigidum.

PubMed

Busi, Roberto; Powles, Stephen B

2016-09-01

Weeds can be a greater constraint to crop production than animal pests and pathogens. Pre-emergence herbicides are crucial in many cropping systems to control weeds that have evolved resistance to selective post-emergence herbicides. In this study we assessed the potential to evolve resistance to the pre-emergence herbicides prosulfocarb + S-metolachlor or pyroxasulfone in 50 individual field Lolium rigidum populations collected in a random survey in Western Australia prior to commercialisation of these pre-emergence herbicides. This study shows for the first time that in randomly collected L. rigidum field populations the selection with either prosulfocarb + S-metolachlor or pyroxasulfone can result in concomitant evolution of resistance to both prosulfocarb + S-metolachlor and pyroxasulfone after three generations. In the major weed L. rigidum, traits conferring resistance to new herbicides can be present before herbicide commercialisation. Proactive and multidisciplinary research (evolutionary ecology, modelling and molecular biology) is required to detect and analyse resistant populations before they can appear in the field. Several studies show that evolved cross-resistance in weeds is complex and often unpredictable. Thus, long-term management of cross-resistant weeds must be achieved through heterogeneity of selection by effective chemical, cultural and physical weed control strategies that can delay herbicide resistance evolution. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Are herbicides a once in a century method of weed control?

PubMed

Davis, Adam S; Frisvold, George B

2017-11-01

The efficacy of any pesticide is an exhaustible resource that can be depleted over time. For decades, the dominant paradigm - that weed mobility is low relative to insect pests and pathogens, that there is an ample stream of new weed control technologies in the commercial pipeline, and that technology suppliers have sufficient economic incentives and market power to delay resistance - supported a laissez faire approach to herbicide resistance management. Earlier market data bolstered the belief that private incentives and voluntary actions were sufficient to manage resistance. Yet, there has been a steady growth in resistant weeds, while no new commercial herbicide modes of action (MOAs) have been discovered in 30 years. Industry has introduced new herbicide tolerant crops to increase the applicability of older MOAs. Yet, many weed species are already resistant to these compounds. Recent trends suggest a paradigm shift whereby herbicide resistance may impose greater costs to farmers, the environment, and taxpayers than earlier believed. In developed countries, herbicides have been the dominant method of weed control for half a century. Over the next half-century, will widespread resistance to multiple MOAs render herbicides obsolete for many major cropping systems? We suggest it would be prudent to consider the implications of such a low-probability, but high-cost development. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Soil management shapes ecosystem service provision and trade-offs in agricultural landscapes.

PubMed

Tamburini, Giovanni; De Simone, Serena; Sigura, Maurizia; Boscutti, Francesco; Marini, Lorenzo

2016-08-31

Agroecosystems are principally managed to maximize food provisioning even if they receive a large array of supporting and regulating ecosystem services (ESs). Hence, comprehensive studies investigating the effects of local management and landscape composition on the provision of and trade-offs between multiple ESs are urgently needed. We explored the effects of conservation tillage, nitrogen fertilization and landscape composition on six ESs (crop production, disease control, soil fertility, water quality regulation, weed and pest control) in winter cereals. Conservation tillage enhanced soil fertility and pest control, decreased water quality regulation and weed control, without affecting crop production and disease control. Fertilization only influenced crop production by increasing grain yield. Landscape intensification reduced the provision of disease and pest control. We also found tillage and landscape composition to interactively affect water quality regulation and weed control. Under N fertilization, conventional tillage resulted in more trade-offs between ESs than conservation tillage. Our results demonstrate that soil management and landscape composition affect the provision of several ESs and that soil management potentially shapes the trade-offs between them. © 2016 The Author(s).

Improving Soil Seed Bank Management.

PubMed

Haring, Steven C; Flessner, Michael L

2018-05-08

Problems associated with simplified weed management motivate efforts for diversification. Integrated weed management uses fundamentals of weed biology and applied ecology to provide a framework for diversified weed management programs; the soil seed bank comprises a necessary part of this framework. By targeting seeds, growers can inhibit the propagule pressure on which annual weeds depend for agricultural invasion. Some current management practices affect weed seed banks, such as crop rotation and tillage, but these tools are often used without specific intention to manage weed seeds. Difficulties quantifying the weed seed bank, understanding seed bank phenology, and linking seed banks to emerged weed communities challenge existing soil seed bank management practices. Improved seed bank quantification methods could include DNA profiling of the soil seed bank, mark and recapture, or 3D LIDAR mapping. Successful and sustainable soil seed bank management must constrain functionally diverse and changing weed communities. Harvest weed seed controls represent a step forward, but over-reliance on this singular technique could make it short-lived. Researchers must explore tools inspired by other pest management disciplines, such as gene drives or habitat modification for predatory organisms. Future weed seed bank management will combine multiple complementary practices that enhance diverse agroecosystems. This article is protected by copyright. All rights reserved.

Crop impactions in bobwhite quail in Louisiana.

PubMed

Hurst, G A

1978-07-01

Crop impactions (solid, hard masses of seeds) caused by seeds of clammy weed (Cuphea carthagenensis) were found in bobwhite quail (Colinus virginianus) killed during the 1965-71 hunting seasons in Louisiana. Emaciation and weakened condition were associated with the presence of crop impactions in two quail, suggesting that physical obstruction of the crop by impactions may be of significant pathologic consequence.

A Guide to Energy Savings - For the Orchard Grower.

ERIC Educational Resources Information Center

Wynn, N. A.

This booklet gives a brief overview of energy use in orchard crop production, and gives examples of cutting costs of fertilization, irrigation, weed management, pest management, high density crops, frost protection, and equipment use. (BB)

Effects of the Integration of Sunn Hemp and Soil Solarization on Plant-Parasitic and Free-Living Nematodes

PubMed Central

Marahatta, Sharadchandra P.; Wang, Koon-Hui; Sipes, Brent S.; Hooks, Cerruti R. R.

2012-01-01

Sunn hemp (SH), Crotolaria juncea, is known to suppress Rotylenchulus reniformis and weeds while enhancing free-living nematodes involved in nutrient cycling. Field trials were conducted in 2009 (Trial I) and 2010 (Trial II) to examine if SH cover cropping could suppress R. reniformis and weeds while enhancing free-living nematodes if integrated with soil solarization (SOL). Cover cropping of SH, soil solarization, and SH followed by SOL (SHSOL) were compared to weedy fallow control (C). Rotylenchulus reniformis population was suppressed by SHSOL at the end of cover cropping or solarization period (Pi) in Trial I, but not in Trial II. However, SOL and SHSOL did not suppress R. reniformis compared to SH in either trial. SH enhanced abundance of bacterivores and suppressed the % herbivores only at Pi in Trial II. At termination of the experiment, SH resulted in a higher enrichment index indicating greater soil nutrient availability, and a higher structure index indicating a less disturbed nematode community compared to C. SOL suppressed bacterivores and fungivores only in Trial II but not in Trial I. On the other hand, SHSOL enhanced bacterivores and fungivores only at Pi in Trial I. Weeds were suppressed by SH, SOL and SHSOL throughout the experiment. SHSOL suppressed R. reniformis and enhanced free-living nematodes better than SOL, and suppressed weeds better than SH. PMID:23482700

The effects of anaerobic soil disinfestation on weed and nematode control, fruit yield and quality of Florida fresh-market tomato

USDA-ARS?s Scientific Manuscript database

Anaerobic soil disinfestation (ASD) is considered a promising sustainable alternative to chemical soil fumigation (CSF), and has been shown to be effective against soil-borne diseases, plant-parasitic nematodes, and weeds in several crop production systems. Nevertheless, limited information is avail...

Microarray and growth analyses identify differences and similarities of early corn response to weeds, shade, and nitrogen stress

USDA-ARS?s Scientific Manuscript database

Weed interference with crop growth is often attributed to water, nutrient, or light competition; however, specific physiological responses to these stresses are not well described. This study’s objective was to compare growth, yield, and gene expression responses of corn to nitrogen (N), low light (...

Influence of weed species and time of glyphosate application on Rhizoctonia root rot of barley

USDA-ARS?s Scientific Manuscript database

Rhizoctonia solani AG-8 causes root disease in wheat, barley, canola and other small grains in the dryland inland Pacific Northwest. The pathogen survives between crops on roots of volunteers and grassy weeds. Destroying this green bridge with herbicides such as glyphosate is a common tactic to cont...

Biodegradation and mineralization of metolachlor and alachlor by Candida xestobii

USDA-ARS?s Scientific Manuscript database

Metolachlor (2-chloro-6’-ethyl-N-(2-methoxy-1-methylethyl) aceto-o-toluidide) is a pre-emergent chloroacetanilide herbicide used to control broadleaf and annual grassy weeds in a variety of crops. The S enantiomer of metolachlor, S-metolachlor, is the most effective form for weed control. While the ...

Net returns and risk for cover crop use as an integrated pest management practice in Alabama cotton production

USDA-ARS?s Scientific Manuscript database

Cotton producers in Alabama are faced with uncertain yields and prices, as well as increasing weed management challenges such as glyphosate resistant weeds. By utilizing a production system that will reduce risk while maintaining yield, cotton production may be economically sustainable into the futu...

Panel Discussion: Weed Management

Treesearch

Don Stringfield

2005-01-01

Successful weed management must be an incorporation of techniques and ideas. Habitual practices of cleaning equipment, using the proper cover crop, spraying small amounts of herbicides early and more often, timing of applications, and the use of the correct mulch/resin are all important lines of attack in keeping the nursery free of competing vegetation. The methods...

Quality Characteristics of Wholemeal Flour and Bread from Durum Wheat (Triticum turgidum L subsp. durum Desf.) after Field Treatment with Plant Water Extracts.

PubMed

Carrubba, Alessandra; Comparato, Andrea; Labruzzo, Andrea; Muccilli, Serena; Giannone, Virgilio; Spina, Alfio

2016-09-01

The use of selected plant water extracts to control pests and weeds is gaining growing attention in organic and sustainable agriculture, but the effects that such extracts may exert on the quality aspects of durum wheat are still unexplored. In 2014, 5 plant water extracts (Artemisia arborescens, Euphorbia characias, Rhus coriaria, Thymus vulgaris, Lantana camara) were prepared and distributed on durum wheat cv Valbelice to evaluate their potential herbicidal effects. After crop harvesting, the major physicochemical and technological parameters of wholemeal flours obtained from each treatment were measured and compared with those from chemical weeding and untreated controls. A baking test was also performed to evaluate the breadmaking quality. In wholemeal flours obtained after the treatment with plant extracts protein and dry gluten content were higher than in control and chemical weeding. Wholemeal flours obtained after chemical weeding reached the highest Mixograph parameters, and that from durum wheat treated with R. coriaria extract demonstrated a very high α-amylase activity. We concluded that the treatments with plant water extracts may influence many quality traits of durum wheat. This occurrence must be taken into account in overall decisions concerning the use of plant extracts in pest and weed management practice. © 2016 Institute of Food Technologists®

Biology, ecology and management of the invasive parthenium weed (Parthenium hysterophorus L.).

PubMed

Adkins, Steve; Shabbir, Asad

2014-07-01

Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening natural ecosystems and agroecosystems in over 30 countries worldwide. Parthenium weed causes losses of crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and resulting in serious economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (namely cultural, mechanical, chemical and biological control) have been used to minimise losses caused by this weed, but most of these approaches are ineffective and uneconomical and/or have limitations. Although chemical control using herbicides and biological control utilising exotic insects and pathogens have been found to contribute to the management of the weed, the weed nevertheless remains a significant problem. An integrated management approach is proposed here for the effective management of parthenium weed on a sustainable basis. © 2014 Society of Chemical Industry.

Impact of Cropping Systems, Soil Inoculum, and Plant Species Identity on Soil Bacterial Community Structure.

PubMed

Ishaq, Suzanne L; Johnson, Stephen P; Miller, Zach J; Lehnhoff, Erik A; Olivo, Sarah; Yeoman, Carl J; Menalled, Fabian D

2017-02-01

Farming practices affect the soil microbial community, which in turn impacts crop growth and crop-weed interactions. This study assessed the modification of soil bacterial community structure by organic or conventional cropping systems, weed species identity [Amaranthus retroflexus L. (redroot pigweed) or Avena fatua L. (wild oat)], and living or sterilized inoculum. Soil from eight paired USDA-certified organic and conventional farms in north-central Montana was used as living or autoclave-sterilized inoculant into steam-pasteurized potting soil, planted with Am. retroflexus or Av. fatua and grown for two consecutive 8-week periods to condition soil nutrients and biota. Subsequently, the V3-V4 regions of the microbial 16S rRNA gene were sequenced by Illumina MiSeq. Treatments clustered significantly, with living or sterilized inoculum being the strongest delineating factor, followed by organic or conventional cropping system, then individual farm. Living inoculum-treated soil had greater species richness and was more diverse than sterile inoculum-treated soil (observed OTUs, Chao, inverse Simpson, Shannon, P < 0.001) and had more discriminant taxa delineating groups (linear discriminant analysis). Living inoculum soil contained more Chloroflexi and Acidobacteria, while the sterile inoculum soil had more Bacteroidetes, Firmicutes, Gemmatimonadetes, and Verrucomicrobia. Organically farmed inoculum-treated soil had greater species richness, more diversity (observed OTUs, Chao, Shannon, P < 0.05), and more discriminant taxa than conventionally farmed inoculum-treated soil. Cyanobacteria were higher in pots growing Am. retroflexus, regardless of inoculum type, for three of the four organic farms. Results highlight the potential of cropping systems and species identity to modify soil bacterial communities, subsequently modifying plant growth and crop-weed competition.

Rye cover crop effects on soil properties in no-till corn silage/soybean agroecosystems

USDA-ARS?s Scientific Manuscript database

Farmers in the U.S. Corn Belt are showing increasing interest in winter cover crops. The known benefits of winter cover crops include reduced nitrate leaching, soil erosion, and weed germination, but evidence of improvements in soil productivity would provide further incentive for famers to implemen...

Effect of roller/crimper designs in terminating rye cover crop in small-scale conservation systems

USDA-ARS?s Scientific Manuscript database

In recent years, use of cover crops in no-till organic production systems has steadily increased. When cover crops are terminated at an appropriate growth stage, the unincorporated residue mulch protects the soil from erosion, runoff, soil compaction, and weed pressure, and conserves soil water. In ...

Short- and full-season soybean in stale seedbeds versus rolled-crimped winter rye mulch

USDA-ARS?s Scientific Manuscript database

Late seedbed preparations (also known as stale or false seedbeds) are used by organic growers to reduce weed populations prior to crop planting. Rye mulches, derived from mechanically killed (rolled and crimped) winter rye cover crops, can serve the same purpose for spring-planted organic crops. Bot...

Weed science and management, in soil sciences, land cover, and land use

USDA-ARS?s Scientific Manuscript database

An integral component of conservation agriculture systems in cotton is the use of a high-residue winter cover crop; however, terminating such cover crops is a cost and planting into high-residue is a challenge. Black oat, rye, and wheat winter cover crops were flattened with a straight-blade mechan...

Crop advisor perceptions of giant ragweed distribution, herbicide-resistance, and management in the Corn Belt

USDA-ARS?s Scientific Manuscript database

Giant ragweed has been increasing as a major weed of row crops in North America. We conducted a web-based survey of Certified Crop Advisors in the Corn Belt to determine the current distribution of giant ragweed, the distribution of herbicide resistant populations, and management and ecological fact...

7 CFR 205.206 - Crop pest, weed, and disease management practice standard.

Code of Federal Regulations, 2013 CFR

2013-01-01

... (CONTINUED) ORGANIC FOODS PRODUCTION ACT PROVISIONS NATIONAL ORGANIC PROGRAM Organic Production and Handling... rotation and soil and crop nutrient management practices, as provided for in §§ 205.203 and 205.205; (2... substance included on the National List of synthetic substances allowed for use in organic crop production...

7 CFR 205.206 - Crop pest, weed, and disease management practice standard.

Code of Federal Regulations, 2014 CFR

2014-01-01

... (CONTINUED) ORGANIC FOODS PRODUCTION ACT PROVISIONS NATIONAL ORGANIC PROGRAM Organic Production and Handling... rotation and soil and crop nutrient management practices, as provided for in §§ 205.203 and 205.205; (2... substance included on the National List of synthetic substances allowed for use in organic crop production...

7 CFR 205.206 - Crop pest, weed, and disease management practice standard.

Code of Federal Regulations, 2012 CFR

2012-01-01

... (CONTINUED) ORGANIC FOODS PRODUCTION ACT PROVISIONS NATIONAL ORGANIC PROGRAM Organic Production and Handling... rotation and soil and crop nutrient management practices, as provided for in §§ 205.203 and 205.205; (2... substance included on the National List of synthetic substances allowed for use in organic crop production...

Allelopathic Effects of Common Landscape and Nursery Mulch Materials on Weed Control

PubMed Central

Saha, Debalina; Marble, S. Chris; Pearson, Brian J.

2018-01-01

Use of organic mulch materials such as pinebark, pinestraw, or various hardwood chips for weed control is a common practice in residential and commercial landscapes. Mulch can inhibit weed seed germination and growth through light exclusion, acting as physical barrier, reducing available moisture to weed seeds within the mulch layer, and through release of allelochemicals that may inhibit germination or growth of some weed species. Previous and current research on allelopathic chemicals present in mulch have focused on cover crops and their residues with an emphasis on agronomic crops. These materials would not be suitable in a landscape setting due to rapid decomposition, lack of commercial availability, and little aesthetic appeal. Research is needed concerning identification, quantification, extraction, mechanism of release, persistence, selectivity, genetic regulation, and mode of action of potential allelochemicals present in mulch materials used for landscape purposes. More knowledge of these natural chemicals could aid practitioners and homeowners in the selection of mulch and identify potential new mulch materials that could be utilized in these industries. The purpose of this review is to summarize previous research pertaining to allelopathic compounds present in commonly used mulch materials and identify new potential mulch materials that could be utilized in the landscape sector based upon allelopathic properties. Current areas where additional research is needed are also identified. PMID:29899752

Uses of thaxtomin and thaxtomin compositions as herbicides

DOEpatents

Koivunen, Marja; Marrone, Pamela

2016-12-27

There is a need for a selective, low-risk herbicide that can be used to control weeds in cereal cultures and turf. The present invention discloses that a bacterial secondary metabolite, thaxtomin and optionally another herbicide is an effective herbicide on broadleaved, sedge and grass weeds. Thaxtomin A and structurally similar compounds can be used as natural herbicides to control the germination and growth of weeds in cereal, turf grass, Timothy grass and pasture grass cultures with no phytotoxicity to these crops. As a natural, non-toxic compound, thaxtomin can be used as a safe alternative for weed control in both conventional and organic farming and gardening systems.

A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems

DOE PAGES

Fischer, M.; Kelley, A. M.; Ward, E. J.; ...

2017-02-03

Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. In order to test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptreemore » (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha -11 under high-inputs and 32.7 Mg ha -1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha -1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha -1. We also found that sycamore showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha -1, suggesting this native species is a poor choice for SRWC. We then conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.« less

A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, M.; Kelley, A. M.; Ward, E. J.

Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. In order to test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptreemore » (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha -11 under high-inputs and 32.7 Mg ha -1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha -1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha -1. We also found that sycamore showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha -1, suggesting this native species is a poor choice for SRWC. We then conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.« less

The role of Bh4 in parallel evolution of hull colour in domesticated and weedy rice.

PubMed

Vigueira, C C; Li, W; Olsen, K M

2013-08-01

The two independent domestication events in the genus Oryza that led to African and Asian rice offer an extremely useful system for studying the genetic basis of parallel evolution. This system is also characterized by parallel de-domestication events, with two genetically distinct weedy rice biotypes in the US derived from the Asian domesticate. One important trait that has been altered by rice domestication and de-domestication is hull colour. The wild progenitors of the two cultivated rice species have predominantly black-coloured hulls, as does one of the two U.S. weed biotypes; both cultivated species and one of the US weedy biotypes are characterized by straw-coloured hulls. Using Black hull 4 (Bh4) as a hull colour candidate gene, we examined DNA sequence variation at this locus to study the parallel evolution of hull colour variation in the domesticated and weedy rice system. We find that independent Bh4-coding mutations have arisen in African and Asian rice that are correlated with the straw hull phenotype, suggesting that the same gene is responsible for parallel trait evolution. For the U.S. weeds, Bh4 haplotype sequences support current hypotheses on the phylogenetic relationship between the two biotypes and domesticated Asian rice; straw hull weeds are most similar to indica crops, and black hull weeds are most similar to aus crops. Tests for selection indicate that Asian crops and straw hull weeds deviate from neutrality at this gene, suggesting possible selection on Bh4 during both rice domestication and de-domestication. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Horseweed control in field nursery crops

USDA-ARS?s Scientific Manuscript database

Horseweed (Conyza canadensis) is one of the most problematic weeds across all crops in agriculture. Its economic impact worsened when it developed resistance to glyphosate-containing herbicides. Nursery growers in the Midwest have recently reported difficulty in controlling horseweed in field-nurs...

ASSESSING THE RISKS OF NON-TARGET TERRESTRIAL PLANTS FROM HERBICIDES

EPA Science Inventory

Use of chemical herbicides to reduce weed competition is a major contributing factor to the high productivity of conventional intensive agricultural cropping systems. However, because of their inherent phytotoxicity, movement of herbicides from target crops and soils can adverse...

Intercropping of oat and field pea in Alaska: an alternative approach to quality forage production and weed control

USDA-ARS?s Scientific Manuscript database

Intercropping of legumes with non-legumes is an ancient crop production method used to improve quality and dry matter (DM) yields of forage and grain, and to control weeds. However, there is little information regarding intercropping at high latitudes. The objectives of this field study were to eval...

Phenotypic Evaluation of Weed-competitive Traits and Yield of Rice RILs from an Indica x Tropical Japonica Mapping Population

USDA-ARS?s Scientific Manuscript database

Indica rice cultivars can suppress weedy grasses. To better understand the important traits and genes underlying weed suppression and crop productivity, a recombinant inbred line (RIL) F8 population was developed by crossing non-suppressive ‘Katy’ and high-yielding, allelopathic ‘PI312777’. Three h...

Herbicides derived from natural products and their role in the integrated management of weeds in organic Vidalia sweet onion

USDA-ARS?s Scientific Manuscript database

Timely cultivation with a tine weeder is the primary tool for successful weed control in organic Vidalia® sweet onion. Vidalia® sweet onion is a cool-season crop and weather conditions frequently arise that delay cultivation. These delays are often caused by excessive rainfall. Herbicides derived...

Weed-cover versus weed-removal management in olive orchards: influence on the carbon balance at the ecosystem scale

NASA Astrophysics Data System (ADS)

Chamizo, Sonia; Serrano-Ortiz, Penélope; Vicente-Vicente, José Luis; Sánchez-Cañete, Enrique P.; López-Ballesteros, Ana; Kowalski, Andrew S.

2016-04-01

Agriculture plays an important role in the C budget at the global scale. Traditional practices based on soil tillage and applying herbicides to remove weeds have caused damage to soils and led to important losses of soil organic C and increased CO2 emissions to the atmosphere. Changing trends from traditional agriculture to conservation agriculture practices may have an important role in both C and water budgets and the transformation of agriculture from C source to C sink. The objective of this study was to analyse the effect of two treatments, weed removal by herbicides versus weed cover conservation, on the C balance in an irrigated olive orchard in SE Spain. Measurements of CO2 exchange were made from October 2014 to September 2015 using two eddy covariance towers, one for each olive crop treatment. Results show that CO2 fluxes at the ecosystem scale were similar in the two treatments during initial conditions, prior to weed growth in the soils without herbicide application (October). During the first week, daily net ecosystem exchange (NEE) was close to zero in both treatments, with values ranging from 1.06 to -0.41 g C m-2 in the weed cover treatment, and from 0.76 to -0.69 g C m-2 in the weed removal treatment. As weed growth increased, higher net CO2 assimilation was found in the treatment with weed cover. In both treatments, maximum net CO2 assimilation was found in March, with a monthly NEE of -72 and -28 g C m-2 in the treatment with and without weed cover, respectively. In May, after the weeds were cut and left on the soil, a strong increase was observed in NEE in the treatment with weed cover due to decreased CO2 assimilation and increased respiration compared to the treatment without weed cover. Therefore, soil chamber measurements showed average respiration rates of 2.57 and 1.57 μmol m-2 s-2 in the weed cover and weed removal treatment, respectively. Finally, the highest monthly NEE was registered during July, with both treatments showing a similar value of NEE (26 and 23 g C m-2). Regarding the annual balance, significant differences were found in NEE between both treatments. The weed cover treatment showed 1.6 times higher annual net C assimilation (-132 g C m-2) than the weed removal treatment (-83 g C m-2). These results highlight the importance of sustainable management practices in agriculture to strengthen the behavior of cropping systems as C sinks.

Identification and discrimination of herbicide residues using a conducting polymer electronic nose

Treesearch

Alphus Dan Wilson

2016-01-01

The identification of herbicide residues on crop foliage is necessary to make crop-management decisions for weed pest control and to monitor pesticide residue levels on food crops. Electronic-nose (e-nose) methods were tested as a cheaper, alternative means of discriminating between herbicide residue types (compared with conventional chromatography methods), by...

Safe, Effective Use of Pesticides, A Manual for Commercial Applicators: Vegetable Pests.

ERIC Educational Resources Information Center

Cress, D.; And Others

This manual is intended to assist pesticide applicators in vegetable crops prepare for certification under the Michigan Pesticide Control Act of 1976. The primary focus of this publication is on vegetable pest control. The three sections presented describe: (1) Insect pests of vegetable crops; (2) Weed pests of vegetable crops; and (3) Causes of…

Use of Cover Crops in Hardwood Production

Treesearch

Randy Rentz

2005-01-01

Cover crops are as essential a practice in hardwood production as in pine production or any other nursery operation. Without proper cover crop rotation in a nursery plan, we open ourselves up to an array of problems: more diseases, wrong pH, more weeds, reduced fertility, and less downward percolation of soil moisture due, in part, to compaction....

Artificial intelligence analysis of hyperspectral remote sensing data for management of water, weed, and nitrogen stresses in corn fields

NASA Astrophysics Data System (ADS)

Waheed, Tahir

This study investigated the possibility of using ground-based remotely sensed hyperspectral observations with a special emphasis on detection of water, weed and nitrogen stresses contributing towards in-season decision support for precision crop management (PCM). A three factor split-split-plot experiment, with four randomized blocks as replicates, was established during the growing seasons of 2003 and 2004. Corn (Zea mays L.) hybrid DKC42-22 was grown because this hybrid is a good performer on light soils in Quebec. There were twelve 12 x 12m plots in a block (one replication per treatment per block) and the total number of plots was 48. Water stress was the main factor in the experiment. A drip irrigation system was laid out and each block was split into irrigated and non-irrigated halves. The second main factor of the experiment was weeds with two levels i.e. full weed control and no weed control. Weed treatments were assigned randomly by further splitting the irrigated and non-irrigated sub-blocks into two halves. Each of the weed treatments was furthermore split into three equal sub-sub-plots for nitrogen treatments (third factor of the experiment). Nitrogen was applied at three levels i.e. 50, 150 and 250 kg N ha-1 (Quebec norm is between 120-160 kg N ha-1). The hyperspectral data were recorded (spectral resolution = 1 nm) mid-day (between 1000 and 1400 hours) with a FieldSpec FR spectroradiometer over a spectral range of 400-2500 run at three growth stages namely: early growth, tasseling and full maturity, in each of the growing season. There are two major original contributions in this thesis: First is the development of a hyperspectral data analysis procedure for separating visible (400-700 nm), near-infrared (700-1300 nm) and mid-infrared (1300-2500 nm) regions of the spectrum for use in discriminant analysis procedure. In addition, of all the spectral band-widths analyzed, seven waveband-aggregates were identified using STEPDISC procedure, which were the most effective for classifying combined water, weed, and nitrogen stress. The second contribution is the successful classification of hyperspectral observations acquired over an agricultural field, using three innovative artificial intelligence approaches; support vector machines (SVM), genetic algorithms (GA) and decision tree (DT) algorithms. These AI approaches were used to evaluate a combined effect of water, weed and nitrogen stresses in corn and of all the three AI approaches used, SVM produced the best results (overall accuracy ranging from 88% to 100%). The general conclusion is that the conventional statistical and artificial intelligence techniques used in this study are all useful for quickly mapping combined affects of irrigation, weed and nitrogen stresses (with overall accuracies ranging from 76% to 100%). These approaches have strong potential and are of great benefit to those investigating the in-season impact of irrigation, weed and nitrogen management for corn crop production and other environment related challenges.

Applying a weed risk assessment approach to GM crops.

PubMed

Keese, Paul K; Robold, Andrea V; Myers, Ruth C; Weisman, Sarah; Smith, Joe

2014-12-01

Current approaches to environmental risk assessment of genetically modified (GM) plants are modelled on chemical risk assessment methods, which have a strong focus on toxicity. There are additional types of harms posed by plants that have been extensively studied by weed scientists and incorporated into weed risk assessment methods. Weed risk assessment uses robust, validated methods that are widely applied to regulatory decision-making about potentially problematic plants. They are designed to encompass a broad variety of plant forms and traits in different environments, and can provide reliable conclusions even with limited data. The knowledge and experience that underpin weed risk assessment can be harnessed for environmental risk assessment of GM plants. A case study illustrates the application of the Australian post-border weed risk assessment approach to a representative GM plant. This approach is a valuable tool to identify potential risks from GM plants.

Augmented multivariate image analysis applied to quantitative structure-activity relationship modeling of the phytotoxicities of benzoxazinone herbicides and related compounds on problematic weeds.

PubMed

Freitas, Mirlaine R; Matias, Stella V B G; Macedo, Renato L G; Freitas, Matheus P; Venturin, Nelson

2013-09-11

Two of major weeds affecting cereal crops worldwide are Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass). Thus, development of new herbicides against these weeds is required; in line with this, benzoxazinones, their degradation products, and analogues have been shown to be important allelochemicals and natural herbicides. Despite earlier structure-activity studies demonstrating that hydrophobicity (log P) of aminophenoxazines correlates to phytotoxicity, our findings for a series of benzoxazinone derivatives do not show any relationship between phytotoxicity and log P nor with other two usual molecular descriptors. On the other hand, a quantitative structure-activity relationship (QSAR) analysis based on molecular graphs representing structural shape, atomic sizes, and colors to encode other atomic properties performed very accurately for the prediction of phytotoxicities of these compounds against wild oat and rigid ryegrass. Therefore, these QSAR models can be used to estimate the phytotoxicity of new congeners of benzoxazinone herbicides toward A. fatua L. and L. rigidum Gaud.

Influence of farm management upon arbuscular mycorrhizal fungi

USDA-ARS?s Scientific Manuscript database

Good farming practices are conducted for a variety of reasons. Farmers now include management practices such as over wintering cover crops, reduced tillage, and crop rotation with the goals of reducing soil erosion, managing nutrient availability, building soil organic matter, controlling weeds, an...

Competition increases sensitivity of wheat (Triticum aestivum) to biotic plant-soil feedback.

PubMed

Hol, W H Gera; de Boer, Wietse; ten Hooven, Freddy; van der Putten, Wim H

2013-01-01

Plant-soil feedback (PSF) and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivity of the focal plant to PSF. In agro-ecosystems each of these two options would yield contrasting outcomes: reduced versus enhanced effects of weeds on crop biomass production. To test the effect of competition on sensitivity to PSF, we grew Triticum aestivum (Common wheat) with and without competition from a weed community composed of Vicia villosa, Chenopodium album and Myosotis arvensis. Plants were grown in sterilized soil, with or without living field inoculum from 4 farms in the UK. In the conditioning phase, field inocula had both positive and negative effects on T. aestivum shoot biomass, depending on farm. In the feedback phase the differences between shoot biomass in T. aestivum monoculture on non-inoculated and inoculated soils had mostly disappeared. However, T. aestivum plants growing in mixtures in the feedback phase were larger on non-inoculated soil than on inoculated soil. Hence, T. aestivum was more sensitive to competition when the field soil biota was present. This was supported by the statistically significant negative correlation between shoot biomass of weeds and T. aestivum, which was absent on sterilized soil. In conclusion, competition in cereal crop-weed systems appears to increase cereal crop sensitivity to soil biota.

Benchmark study on glyphosate-resistant cropping systems in the United States. Part 3: Grower awareness, information sources, experiences and management practices regarding glyphosate-resistant weeds.

PubMed

Givens, Wade A; Shaw, David R; Newman, Michael E; Weller, Stephen C; Young, Bryan G; Wilson, Robert G; Owen, Micheal D K; Jordan, David L

2011-07-01

A survey was conducted with nearly 1200 growers in US states (Illinois, Indiana, Iowa, Mississippi, Nebraska and North Carolina) in 2005 with the objective in part of determining the awareness of the potential for development of glyphosate resistance, the experience with glyphosate-resistant (GR) weeds and the sources of information that growers had utilized for information on glyphosate resistance. Growers were asked a series of questions to determine the level of glyphosate resistance awareness and to list the sources of information used to learn about glyphosate resistance issues. The majority of the growers (88%) were aware of a weed's potential to evolve resistance to herbicide, while 44% were aware of state-specific documented cases of GR weeds, and 15% reported having had personal experience with GR weeds. Among sources of information concerning glyphosate resistance issues, farm publications, dealers/retailers and university/extension were the most frequent responses (41, 17 and 14% respectively). Based on a 1-10 effectiveness scale, growers ranked tillage the least effective practice (5.5) and using the correct label rates of herbicides at the proper timing for the size and type of weeds present the most effective practice (8.6) with respect to how effectively the practices mitigated the evolution of GR weeds. Results from this survey can be used by researchers, extension specialists and crop advisors further to bridge the information gap between growers and themselves and better to disseminate information concerning glyphosate resistance and glyphosate resistance management practices through more targeted information and information delivery methods. Copyright © 2011 Society of Chemical Industry.

[Effects of different fertilization regimes on weed communities in wheat fields under rice-wheat cropping system].

PubMed

Yuan, Fang; Li, Yong; Li, Fen-hua; Sun, Guo-jun; Han, Min; Zhang, Hai-yan; Ji, Zhong; Wu, Chen-yu

2016-01-01

To reveal the effects of different fertilization regimes on weed communities in wheat fields under a rice-wheat rotation system, a survey was conducted before wheat harvest in 2014 after a 4-year long-term recurrent fertilization scheme. Weed species types, density, height and diversity index under different fertilization and straw-returning schemes in wheat fields were studied and complemented with a canonical correspondence analysis on weed community distribution and soil nutrient factors. Twenty weed species were recorded among 36 wheat fields belonging to 19 genera and 11 families. Beckmannia syzigachne, Hemistepta lyrata, Malachium aquaticum and Cnidium monnieri were widely distributed throughout the sampled area. Long-term fertilization appeared to reduce weed species richness and density, particularly for broadleaf weeds, but increased weed height. Diversity and evenness indices of weed communities were lower and dominance indices were higher in fields where chemical fertilizers were applied alone or combined with organic fertilizers, especially, where organic-inorganic compound fertilizer was used, in which it readily caused the outbreak of a dominant species and severe damage. Conversely, diversity and evenness indices of weed communities were higher and dominance indices were lower when the straw was returned to the field combined with chemical or organic fertilizers, in which weed community structures were complex and stable with lower weed density. Under these conditions weeds only caused slight reduction of wheat growth.

Carbon Balance in an Olive Orchard of SE Spain: Influence of Weed Cover

NASA Astrophysics Data System (ADS)

Sanchez-Canete, E. P.; Chamizo, S.; Serrano-Ortiz, P.; Lopez-Ballesteros, A.; Vicente-Vicente, J. L.; Kowalski, A. S.

2016-12-01

Agriculture is largely responsible for greenhouse gas emissions due to deforestation, land use changes and inadequate practices. High carbon (C) losses in agricultural lands caused by inadequate soil management entail a reduction of their C sequestration capacity and make agriculture more vulnerable to climate change impact. However, this trend can be potentially reversed if adequate agricultural practices are applied. Olive trees are one of the most widespread crops in the Mediterranean region, especially in Spain. Due to climate characteristics of the Mediterranean region and soils characterized by poor structure and low organic matter content, these crops are subject to environmental problems including erosion, soil compaction, and the loss of soil fertility that, indeed, can be aggravated by conventional practices such as intensive tillage. No-till agriculture and maintenance of the spontaneous resident vegetation cover (hereinafter, "weeds") have been applied in olive orchards in order to reduce erosion and increase soil organic C content. However, the role of these conservation practices in C balance at ecosystem scale has not been assessed so far. In this study, we analyzed the influence of weeds against weed removal via herbicide application on the net ecosystem CO2 exchange (NEE) in an olive orchard in Jaén (SE Spain), by using two eddy covariance towers during the hydrological year 2014-2015. We found that the presence of weeds increased net C uptake during winter and early spring. However, after weeds were mowed in April and kept on the soil, net C uptake decreased in this treatment due to an increase in soil respiration. Despite the lower net C uptake observed during late spring, the presence of weeds increased C fixation at annual scale. During the year of study, the weed removal practice decreased C uptake by 50% compared to the olive orchard where weeds were kept. We conclude that maintenance of weeds in olive groves has a positive effect on CO2 sequestration and enhances the capacity of this agro-system to act as a net CO2 sink.

Impact of the timing and duration of weed control on the establishment of a rubber tree plantation.

PubMed

Guzzo, Caio D; Carvalho, Leonardo B de; Giancotti, Paulo R F; Alves, Pedro L C A; Gonçalves, Elaine C P; Martins, José V F

2014-03-01

Rubber tree production is reduced by weeds that compete for environmental resources; therefore, the timing and duration of weed control influences weed interference. The objectives of this study were to evaluate the growth of rubber tree (Hevea brasiliensis) plants, to determine the critical period for weed control, and to evaluate the growth recovery of rubber trees that coexisted with weeds for different periods of time after planting. Two groups of treatments were established under field conditions in the first year of the investigation: one group contained crescent periods of weed infestation, while the other contained crescent periods of weed control, also including a weed-free check and a total weedy check. In the second year of the investigation, the weeds were totally controlled. Urochloa decumbens was the dominant weed (over 90% groundcover). Crop growth was greatly reduced due to the weed interference. Plant height decreased more rapidly than did any other characteristic. Plant height, leaf dry mass, and leaf area decreased by 99%, 97% and 96%, respectively, and were the most reduced characteristics. Plant height also recovered more rapidly than did any characteristic when the period of weed control was lengthened. However, stem dry mass increased by 750%, making it the most recovered characteristic. The critical period for weed control was between 4 and 9½ months after planting in the first year; however, the rubber trees showed an expressive growth recovery when the weeds were controlled throughout the second year.

40 CFR 80.1401 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of pressure that is produced through the conversion of organic matter. Only biogas that is used as... crops, crop residue, or livestock, or records of purchases for land treatments such as fertilizer, weed... ecologically sensitive forestland. (5) Biomass (organic matter that is available on a renewable or recurring...

Vegetable soybean tolerance to pyroxasulfone

USDA-ARS?s Scientific Manuscript database

If registered for use on vegetable soybean, pyroxasulfone would fill an important gap in weed management systems in the crop. In order to determine the potential crop injury risk of pyroxasulfone on vegetable soybean, the objective of this work was to quantify vegetable soybean tolerance to pyroxasu...

Xanthium strumarium: a weed host of components of begomovirus-betasatellite complexes affecting crops.

PubMed

Mubin, M; Akhtar, S; Amin, I; Briddon, R W; Mansoor, S

2012-02-01

Xanthium strumarium is a common weed that often shows symptoms typical of begomovirus infection, such as leaf curling and vein thickening. The virus complex isolated from the weed consisted of two begomoviruses along with a betasatellite and an alphasatellite. The first begomovirus was shown to be an isolate of Cotton leaf curl Burewala virus, a new recombinant begomovirus species that is associated with resistance breaking in previously resistant cotton varieties in Pakistan, whereas the second was shown to be an isolate of Tomato leaf curl Gujarat virus (ToLCGV), a begomovirus previously reported to be bipartite. However, there was no evidence for the presence of the second genomic component, DNA B, of ToLCGV in X. strumarium. The betasatellite was shown to be an isolate of Tomato yellow leaf curl Thailand betasatellite, the first time this satellite has been identified in Pakistan. The alphasatellite associated with infection of X. strumarium was shown to be a species recently identified in potato and various weeds; Potato leaf curl alphasatellite. Although each component has been identified previously, this is the first time they have been identified in a single host. These findings reinforce the hypothesis that weeds are reservoirs of crop-infecting begomoviruses that may contribute to virus diversity by virtue of harboring multiple viruses and virus associated components, which may lead to interspecific recombination and component exchange.

Phytotoxicity Study on Bidens sulphurea Sch. Bip. as a Preliminary Approach for Weed Control.

PubMed

da Silva, Bruna P; Nepomuceno, Mariluce P; Varela, Rosa M; Torres, Ascensión; Molinillo, José M G; Alves, Pedro L C A; Macías, Francisco A

2017-06-28

Farmers of the Franca region in Brazil observed that Bidens sulphurea was able to eliminate the Panicum maximum weed, which infected coffee plantations, without affecting the crop. In an effort to determine if the inhibitory effects observed were due to the presence of phytotoxic compounds from leaves and roots, a biodirected isolation and spectroscopic characterization has been carried out. The leaf dichloromethane and root acetone extracts were the most active, and the former appeared to be more phytotoxic to the target species, including four weeds. A total of 26 compounds were isolated from leaves and roots, and four of them are described here for the first time. The major compounds in the leaf extract are the sesquiterpene lactones costunolide, reynosin, and santamarine, and these showed marked inhibition. Amaranthus viridis and Panicum maximum were the most sensitive species of the weeds tested. These three phytotoxic lactones were also evaluated on A. viridis and P. maximum under hydroponic conditions. A. viridis was the most affected species with the three lactones, and santamarine was the most phytotoxic compound on both. This is the first time that the phytotoxicity of sesquiterpene lactones has been evaluated on hydroponic culture. The work described here is a preliminary approach for the use of B. sulphurea for weed control in agriculture, both as a cover crop and by use of its components as natural herbicide leads.

Comparative impact of genetically modified and non modified maize (Zea mays L.) on succeeding crop and associated weed.

PubMed

Ibrahim, Muhammad; Ahmed, Naseer; Ullah, Faizan; Shinwari, Zabta Khan; Bano, Asghari

2016-04-01

This research work documents the comparative impact of genetically modified (GM) (insect resistance) and non modified maize (Zea mays L.) on growth and germination of succeeding crop wheat (Triticum aestivum L.) and associated weed (Avena fatua L.). The aqueous extracts of both the GM and non-GM maize exhibited higher phenolic content than that of methanolic extracts. Germination percentage and germination index of wheat was significantly decreased by GM methanolic extract (10%) as well as that of non-GM maize at 3% aqueous extract. Similarly germination percentage of weed (Avena fatua L.) was significantly reduced by application of 3% and 5% methanolic GM extracts. All extracts of GM maize showed non-significant effect on the number of roots, root length and shoot length per plant but 5% and 10% methanolic extracts of non-GM maize significantly increased the number of roots per plant of wheat seedling. Similarly, 10% methanolic extract of GM maize significantly increased the number of roots per plant of weed seedling. Methanolic extracts of GM and non-GM maize (3% and 5%) significantly decreased the protease activity in wheat as compared to untreated control. © The Author(s) 2013.

Sugarcane crop residue and bagasse allelopathic impact on oat (Avena sative L.), tall morningglory (Ipomoea purpurea L. Roth), and redroot pigweed (Amaranthus retroflexus L.) germination

USDA-ARS?s Scientific Manuscript database

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, and can include compounds released from a crop that adversely impact crop or weed species. The objective of this research was to determine the allelopathic impact of sugarcane (Sacchar...

Effects of weed cover composition on insect pest and natural enemy abundance in a field of Dracaena marginata (Asparagales: Asparagaceae) in Costa Rica.

PubMed

Sadof, Clifford S; Linkimer, Mildred; Hidalgo, Eduardo; Casanoves, Fernando; Gibson, Kevin; Benjamin, Tamara J

2014-04-01

Weeds and their influence on pest and natural enemy populations were studied on a commercial ornamental farm during 2009 in the Atlantic Zone of Costa Rica. A baseline survey of the entire production plot was conducted in February, along a 5 by 5 m grid to characterize and map initial weed communities of plants, cicadellids, katydids, and armored scales. In total, 50 plant species from 21 families were found. Seven weed treatments were established to determine how weed manipulations would affect communities of our targeted pests and natural enemies. These treatments were selected based on reported effects of specific weed cover on herbivorous insects and natural enemies, or by their use by growers as a cover crop. Treatments ranged from weed-free to being completely covered with endemic species of weeds. Although some weed treatments changed pest abundances, responses differed among arthropod pests, with the strongest effects observed for Caldwelliola and Empoasca leafhoppers. Removal of all weeds increased the abundance of Empoasca, whereas leaving mostly cyperacaeous weeds increased the abundance of Caldwelliola. Weed manipulations had no effect on the abundance of katydid and scale populations. No weed treatment reduced the abundance of all three of the target pests. Differential responses of the two leafhopper species to the same weed treatments support hypotheses, suggesting that noncrop plants can alter the abundance of pests through their effects on arthropod host finding and acceptance, as well as their impacts on natural enemies.

The century experiment: the first twenty years of UC Davis' Mediterranean agroecological experiment.

PubMed

Wolf, Kristina M; Torbert, Emma E; Bryant, Dennis; Burger, Martin; Denison, R Ford; Herrera, Israel; Hopmans, Jan; Horwath, Will; Kaffka, Stephen; Kong, Angela Y Y; Norris, R F; Six, Johan; Tomich, Thomas P; Scow, Kate M

2018-02-01

The Century Experiment at the Russell Ranch Sustainable Agriculture Facility at the University of California, Davis provides long-term agroecological data from row crop systems in California's Central Valley starting in 1993. The Century Experiment was initially designed to study the effects of a gradient of water and nitrogen availability on soil properties and crop performance in ten different cropping systems to measure tradeoffs and synergies between agricultural productivity and sustainability. Currently systems include 11 different cropping systems-consisting of four different crops and a cover crop mixture-and one native grass system. This paper describes the long-term core data from the Century Experiment from 1993-2014, including crop yields and biomass, crop elemental contents, aerial-photo-based Normalized Difference Vegetation Index data, soil properties, weather, chemical constituents in irrigation water, winter weed populations, and operational data including fertilizer and pesticide application amounts and dates, planting dates, planting quantity and crop variety, and harvest dates. This data set represents the only known long-term set of data characterizing food production and sustainability in irrigated and rainfed Mediterranean annual cropping systems. There are no copyright restrictions associated with the use of this dataset. © 2018 by the Ecological Society of America.

Characterizing Chickpeas for End Use Characteristics

USDA-ARS?s Scientific Manuscript database

In the United States, cool-season grain legumes, including chickpeas, are integral components of cereal-based cropping systems in the Pacific Northwest and the Upper Midwest. The addition of a pulse crop helps break disease and weed cycles and adds nitrogen and organic matter to the soil. In this ...

Optimizing Alternative Fumigant Applications for Ornamental Production in Florida

USDA-ARS?s Scientific Manuscript database

In Florida, cut flower and other ornamental crop producers have a very limited number of alternatives to methyl bromide for several reasons including the lack of registered herbicides available for these crops, and the need to control previously planted cultivars volunteering as weeds within the sam...

Utilization of sunn hemp for cover crops and weed control in temperate climates

USDA-ARS?s Scientific Manuscript database

The need to develop increasingly integrated pest management and sustainable food production systems has encouraged a greater interest to thoroughly evaluate effective utilization of cover crops in agricultural systems. Sunn hemp, a tropical legume that originated most likely from the Indo-Pakistani ...

Vegetable Crop Pests. MEP 311.

ERIC Educational Resources Information Center

Kantzes, James G.; And Others

As part of a cooperative extension service series by the University of Maryland, this publication introduces the identification and control of common agricultural pests of vegetable crops. The first of the five sections defines "pest" and "weed" and generally introduces different kinds of pests in the categories of insects,…

Fall cover crops boost soil arbuscular mycorrhizal fungi which can lead to reduced inputs

USDA-ARS?s Scientific Manuscript database

Fall cover crops provide multiple benefits to producers. These benefits include pathogen and pest protection, drought protection, weed control, reduced soil erosion, nutrient acquisition and retention, increased soil organic matter, and conservation of soil water by improvement of soil structure th...

Integration of agronomic practices with herbicides for sustainable weed management in aerobic rice.

PubMed

Anwar, M P; Juraimi, A S; Mohamed, M T M; Uddin, M K; Samedani, B; Puteh, A; Man, Azmi

2013-01-01

Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point.

Integration of Agronomic Practices with Herbicides for Sustainable Weed Management in Aerobic Rice

PubMed Central

Anwar, M. P.; Juraimi, A. S.; Mohamed, M. T. M.; Uddin, M. K.; Samedani, B.; Puteh, A.; Man, Azmi

2013-01-01

Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point. PMID:24223513

Emerging Challenges and Opportunities for Education and Research in Weed Science

PubMed Central

Chauhan, Bhagirath S.; Matloob, Amar; Mahajan, Gulshan; Aslam, Farhena; Florentine, Singarayer K.; Jha, Prashant

2017-01-01

In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential. PMID:28928765

Emerging Challenges and Opportunities for Education and Research in Weed Science.

PubMed

Chauhan, Bhagirath S; Matloob, Amar; Mahajan, Gulshan; Aslam, Farhena; Florentine, Singarayer K; Jha, Prashant

2017-01-01

In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential.

Barriers to implementing climate resilient agricultural strategies: The case of crop diversification in the U.S. Corn Belt

Treesearch

Gabrielle E. Roesch-McNally; J.G. Arbuckle; John C. Tyndall

2018-01-01

Cropping system diversity can help build greater agroecosystem resilience by suppressing insect, weed, and disease pressures while also mitigating effects of extreme and more variable weather. Despite the potential benefits of cropping systems diversity, few farmers in the US Corn Belt use diverse rotations. This study examines factors that may influence farmers’...

GM as a route for delivery of sustainable crop protection.

PubMed

Bruce, Toby J A

2012-01-01

Modern agriculture, with its vast monocultures of lush fertilized crops, provides an ideal environment for adapted pests, weeds, and diseases. This vulnerability has implications for food security: when new pesticide-resistant pest biotypes evolve they can devastate crops. Even with existing crop protection measures, approximately one-third yield losses occur globally. Given the projected increase in demand for food (70% by 2050 according to the UN), sustainable ways of preventing these losses are needed. Development of resistant crop cultivars can make an important contribution. However, traditional crop breeding programmes are limited by the time taken to move resistance traits into elite crop genetic backgrounds and the limited gene pools in which to search for novel resistance. Furthermore, resistance based on single genes does not protect against the full spectrum of pests, weeds, and diseases, and is more likely to break down as pests evolve counter-resistance. Although not necessarily a panacea, GM (genetic modification) techniques greatly facilitate transfer of genes and thus provide a route to overcome these constraints. Effective resistance traits can be precisely and conveniently moved into mainstream crop cultivars. Resistance genes can be stacked to make it harder for pests to evolve counter-resistance and to provide multiple resistances to different attackers. GM-based crop protection could substantially reduce the need for farmers to apply pesticides to their crops and would make agricultural production more efficient in terms of resources used (land, energy, water). These benefits merit consideration by environmentalists willing to keep an open mind on the GM debate.

Soil microbial community structure and target organisms under different fumigation treatments

USDA-ARS?s Scientific Manuscript database

Several high-value crop producers in California rely heavily on soil fumigants to control key diseases, nematodes, weeds and volunteer crops. Fumigants with broad biocidal activity can affect both target and non-target soil organisms. The ability of non-target soil organisms to recover after fumigat...

Vegetable Response to Herbicides Applied to Low-Density Polyethylene Mulch Prior to Transplant

USDA-ARS?s Scientific Manuscript database

Few herbicides are available for weed control in vegetables. The elimination of methyl bromide increases the need for herbicides. An experiment was conducted to evaluate crop injury from herbicides applied to LDPE mulch prior to transplant. Irrigation (1 cm) or no irrigation following crop transplan...

Field and Forage Crop Pests. MEP 310.

ERIC Educational Resources Information Center

Morgan, Omar, D.; And Others

As part of a cooperative extension service series by the University of Maryland, this publication introduces the identification and control of common agricultural pests that can be found in field and forage crops. The first of the five sections defines "pest" and "weed" and generally introduces different kinds of pests in the…

Cover crop, soil amendments, and variety effects on organic rice production in Texas

USDA-ARS?s Scientific Manuscript database

The major challenges in organic rice production include nutrient improvement, weed management, and variety selection. In this study, we tested the effects of two soil amendments on organic production in southcentral USA. The 2011-12 winter cover crops were established successfully with full coverage...

Over-the-top broadcast applications of ammonium nonanoate on onion weed control, crop injury, and yields

USDA-ARS?s Scientific Manuscript database

Racer (registered trademark) (40% ammonium nonanoate) is a potential herbicide for organically grown food crops. Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma to determine the effect of applicatio...

Over-the-top broadcast applications of Racer® on onion weed control, crop injury, and yields

USDA-ARS?s Scientific Manuscript database

Racer (registered trademark) (40% ammonium nonanoate) is a potential herbicide for organically grown food crops. Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma to determine the effect of applicatio...

Tolerance of broccoli cultivars to pre-transplanting clomazone

USDA-ARS?s Scientific Manuscript database

Clomazone has been used for weed management in cabbage (Brassica oleracea L., capitata group) production in the U.S. for over 20 years; however, the herbicide is not currently registered for other crop groups within B. oleracea. The U.S. specialty crop pesticide registration program (The IR-4 Proje...

The contribution of arbusclar mycorrhizal fungi to the success or failure of agricultural practices

USDA-ARS?s Scientific Manuscript database

Good farming practices are conducted for a variety of reasons. Farmers now include management practices such as over wintering cover crops, reduced tillage, and crop rotation with the goals of reducing soil erosion, managing nutrient availability, building soil organic matter, controlling weeds, an...

Reduced-tillage organic corn production in a hairy vetch cover crop

USDA-ARS?s Scientific Manuscript database

There is much interest in developing no-tillage systems for organic farming, however, potential limitations include the inability to control weeds and to provide sufficient crop available N. A three-year field experiment was conducted on organically-certified land to explore the use of roller-crimp...

Improving the Agronomy of Alyssum murale for Extensive Phytomining: A Five-Year Field Study.

PubMed

Bani, Aida; Echevarria, Guillaume; Sulçe, Sulejman; Morel, Jean Louis

2015-01-01

Large ultramafic areas exist in Albania, which could be suitable for phytomining with native Alyssum murale. We undertook a five-year field experiment on an ultramafic Vertisol, aimed at optimizing a low-cost Ni-phytoextraction crop of A. murale which is adapted to the Balkans. The following aspects were studied on 18-m2 plots in natural conditions: the effect of (i) plant phenology and element distribution, (ii) plant nutrition and fertilization, (iii) plant cover and weed control and (iv), planting technique (natural cover vs. sown crop). The optimal harvest time was set at the mid-flowering stage when Ni concentration and biomass yield were highest. The application of N, P, and K fertilizers, and especially a split 100-kg ha(-1) N application, increased the density of A. murale against all other species. It significantly increased shoot yield, without reducing Ni concentration. In natural stands, the control of graminaceous weeds required the use of an anti-monocots herbicide. However, after the optimization of fertilization and harvest time, weed control procured little benefit. Finally, cropping sown A. murale was more efficient than enhancing native stands and gave higher biomass and phytoextraction yields; biomass yields progressively improved from 0.3 to 9.0 t ha(-1) and phytoextracted Ni increased from 1.7 to 105 kg ha(-1).

[Effect of tillage patterns on the structure of weed communities in oat fields in the cold and arid region of North China].

PubMed

Zhang, Li; Zhang, Li; Wu, Dong-Xia; Zhang, Jun-Jun

2014-06-01

In order to clarify the effects of tillage patterns on farmland weed community structure and crop production characteristics, based on 10 years location experiment with no-tillage, subsoiling and conventional tillage in the cold and arid region of North China, and supplementary experiment of plowing after 10 years no-tillage and subsoiling, oat was planted in 2 soils under different tillage patterns, and field weed total density, dominant weed types, weed diversity index, field weed biomass and oats yield were measured. The results showed that the regional weed community was dominated by foxtail weed (Setaira viridis); the weed density under long-term no-tillage was 2.20-5.14 times of tillage at different growing stages of oat, but there were no significant differences between conditional tillage and plowing after long-term no-tillage and subsoiling. Field weed Shannon diversity indices were 0.429 and 0.531, respectively, for sandy chestnut soil and loamy meadow soil under no-tillage conditions, and field weed biomass values were 1.35 and 2.26 times of plowing treatment, while the oat biomass values were only 2807.4 kg x hm(-2) and 4053.9 kg x hm(-2), decreased by 22.3% and 46.2%, respectively. The results showed that the weed community characteristics were affected by both tillage patterns and soil types. Long-term no-tillage farmland in the cold and arid region of North China could promote the natural evolution of plant communities by keeping more perennial weeds, and the plowing pattern lowered the annual weed density, eliminated perennial weeds with shallow roots, and stimulated perennial weeds with deep roots.

Unravelling the beneficial role of microbial contributors in reducing the allelopathic effects of weeds.

PubMed

Mishra, Sandhya; Upadhyay, Ram Sanmukh; Nautiyal, Chandra Shekhar

2013-07-01

The field of allelopathy is one of the most fascinating but controversial processes in plant ecology that offers an exciting, interdisciplinary, complex, and challenging study. In spite of the established role of soil microbes in plant health, their role has also been consolidated in studies of allelopathy. Moreover, allelopathy can be better understood by incorporating soil microbial ecology that determines the relevance of allelopathy phenomenon. Therefore, while discussing the role of allelochemicals in plant-plant interactions, the dynamic nature of soil microbes should not be overlooked. The occurrence and toxicity of allelochemicals in soil depend on various factors, but the type of microflora in the surroundings plays a crucial role because it can interfere with its allelopathic nature. Such microbes could be of prime importance for biological control management of weeds reducing the cost and ill effects of chemical herbicides. Among microbes, our main focus is on bacteria--as they are dominant among other microbes and are being used for enhancing crop production for decades--and fungi. Hence, to refer to both bacteria and fungi, we have used the term microbes. This review discusses the beneficial role of microbes in reducing the allelopathic effects of weeds. The review is mainly focused on various functions of bacteria in (1) reducing allelopathic inhibition caused by weeds to reduce crop yield loss, (2) building inherent defense capacity in plants against allelopathic weed, and (3) deciphering beneficial rhizospheric process such as chemotaxis/biofilm, degradation of toxic allelochemicals, and induced gene expression.

Changes over time in the allelochemical content of ten cultivars of rye (Secale cereale L.).

PubMed

Reberg-Horton, S Chris; Burton, James D; Danehower, David A; Ma, Guoying; Monks, David W; Murphy, J Paul; Ranells, Noah N; Williamson, John D; Creamer, Nancy G

2005-01-01

Published studies focused on characterizing the allelopathy-based weed suppression by rye cover crop mulch have provided varying and inconsistent estimates of weed suppression. Studies were initiated to examine several factors that could influence the weed suppressiveness of rye: kill date, cultivar, and soil fertility. Ten cultivars of rye were planted with four rates of nitrogen fertilization, and tissue from each of these treatment combinations was harvested three times during the growing season. Concentrations of a known rye allelochemical DIBOA (2,4-dihydroxy-1,4-(2H)benzoxazine-3-one) were quantified from the harvested rye tissue using high performance liquid chromatography (HPLC). Phytotoxicity observed from aqueous extracts of the harvested rye tissue correlated with the levels of DIBOA recovered in harvested tissue. The amount of DIBOA in rye tissue varied depending on harvest date and rye cultivar, but was generally lower with all cultivars when rye was harvested later in the season. However, the late maturing variety 'Wheeler' retained greater concentrations of DIBOA in comparison to other rye cultivars when harvested later in the season. The decline in DIBOA concentrations as rye matures, and the fact that many rye cultivars mature at different rates may help explain why estimates of weed suppression from allelopathic agents in rye have varied so widely in the literature.

Achieving food security for one million sub-Saharan African poor through push-pull innovation by 2020.

PubMed

Khan, Zeyaur R; Midega, Charles A O; Pittchar, Jimmy O; Murage, Alice W; Birkett, Michael A; Bruce, Toby J A; Pickett, John A

2014-04-05

Food insecurity is a chronic problem in Africa and is likely to worsen with climate change and population growth. It is largely due to poor yields of the cereal crops caused by factors including stemborer pests, striga weeds and degraded soils. A platform technology, 'push-pull', based on locally available companion plants, effectively addresses these constraints resulting in substantial grain yield increases. It involves intercropping cereal crops with a forage legume, desmodium, and planting Napier grass as a border crop. Desmodium repels stemborer moths (push), and attracts their natural enemies, while Napier grass attracts them (pull). Desmodium is very effective in suppressing striga weed while improving soil fertility through nitrogen fixation and improved organic matter content. Both companion plants provide high-value animal fodder, facilitating milk production and diversifying farmers' income sources. To extend these benefits to drier areas and ensure long-term sustainability of the technology in view of climate change, drought-tolerant trap and intercrop plants are being identified. Studies show that the locally commercial brachiaria cv mulato (trap crop) and greenleaf desmodium (intercrop) can tolerate long droughts. New on-farm field trials show that using these two companion crops in adapted push-pull technology provides effective control of stemborers and striga weeds, resulting in significant grain yield increases. Effective multi-level partnerships have been established with national agricultural research and extension systems, non-governmental organizations and other stakeholders to enhance dissemination of the technology with a goal of reaching one million farm households in the region by 2020. These will be supported by an efficient desmodium seed production and distribution system in eastern Africa, relevant policies and stakeholder training and capacity development.

Malaysian weedy rice shows its true stripes: wild Oryza and elite rice cultivars shape agricultural weed evolution in Southeast Asia.

PubMed

Song, Beng-Kah; Chuah, Tse-Seng; Tam, Sheh May; Olsen, Kenneth M

2014-10-01

Weedy rice is a close relative of domesticated rice (Oryza sativa) that competes aggressively with the crop and limits rice productivity worldwide. Most genetic studies of weedy rice have focused on populations in regions where no reproductively compatible wild Oryza species occur (North America, Europe and northern Asia). Here, we examined the population genetics of weedy rice in Malaysia, where wild rice (O. rufipogon) can be found growing in close proximity to cultivated and weedy rice. Using 375 accessions and a combined analysis of 24 neutral SSR loci and two rice domestication genes (sh4, controlling seed shattering, and Bh4, controlling hull colour), we addressed the following questions: (i) What is the relationship of Malaysian weedy rice to domesticated and wild rice, and to weedy rice strains in the USA? (ii) To what extent does the presence of O. rufipogon influence the genetic and phenotypic diversity of Malaysian weeds? (iii) What do the distributions of sh4 and Bh4 alleles and associated phenotypes reveal about the origin and contemporary evolution of Malaysian weedy rice? Our results reveal the following: independent evolutionary origins for Malaysian weeds and US strains, despite their very close phenotypic resemblance; wild-to-weed gene flow in Malaysian weed populations, including apparent adaptive introgression of seed-shattering alleles; and a prominent role for modern Malaysian cultivars in the origin and recent proliferation of Malaysian weeds. These findings suggest that the genetic complexity and adaptability of weedy crop relatives can be profoundly influenced by proximity to reproductively compatible wild and domesticated populations. © 2014 John Wiley & Sons Ltd.

First report of tomato chlorotic spot virus in non-solanaceous weeds erect spiderling (Boerhavia erecta) and asian spiderflower (Cleome viscosa), and sweet chili pepper (Capsicum chinense) in Puerto Rico

USDA-ARS?s Scientific Manuscript database

Tomato chlorotic spot virus (TCSV) has recently been detected in tomato, bell pepper, jimsonweed and lettuce in Puerto Rico. Observations of weeds and additional crops in 2015 and 2016 revealed TCSV-like symptoms. Testing of these symptomatic plants identified three new hosts of TCSV in Puerto Ric...

Mitigation of indirect environmental effects of GM crops

PubMed Central

Pidgeon, J.D; May, M.J; Perry, J.N; Poppy, G.M

2007-01-01

Currently, the UK has no procedure for the approval of novel agricultural practices that is based on environmental risk management principles. Here, we make a first application of the ‘bow-tie’ risk management approach in agriculture, for assessment of land use changes, in a case study of the introduction of genetically modified herbicide tolerant (GMHT) sugar beet. There are agronomic and economic benefits, but indirect environmental harm from increased weed control is a hazard. The Farm Scale Evaluation (FSE) trials demonstrated reduced broad-leaved weed biomass and seed production at the field scale. The simplest mitigation measure is to leave a proportion of rows unsprayed in each GMHT crop field. Our calculations, based on FSE data, show that a maximum of 2% of field area left unsprayed is required to mitigate weed seed production and 4% to mitigate weed biomass production. Tilled margin effects could simply be mitigated by increasing the margin width from 0.5 to 1.5 m. Such changes are cheap and simple to implement in farming practices. This case study demonstrates the usefulness of the bow-tie risk management approach and the transparency with which hazards can be addressed. If adopted generally, it would help to enable agriculture to adopt new practices with due environmental precaution. PMID:17439853

Glyphosate sub-lethal toxicity to non-target organisms occurring in Jatropha curcas plantations in Brazil.

PubMed

de Saraiva, Althiéris Souza; Sarmento, Renato Almeida; Pedro-Neto, Marçal; Teodoro, Adenir Vieira; Erasmo, Eduardo Andrea Lemus; Belchior, Diana Cléssia Vieira; de Azevedo, Emiliano Brandão

2016-10-01

Weed management in physic nut plantations has generally been performed by spraying the herbicide glyphosate. However, the effects of glyphosate on non-target organisms present in the crop system are unknown. Here, we evaluated the toxicity of glyphosate (Roundup Transorb(®)) against the pest species Polyphagotarsonemus latus (Acari: Tarsonemidae) and Tetranychus bastosi (Acari: Tetranychidae) which can be exposed by drift. These mites are considered pests of the physic nut; however, they can also feed and reside on weeds associated with the crop, serving as food sources for predatory mites. When subjected to residue (by ingestion of sap of treated plants), and direct contact to glyphosate, P. latus reproduction was affected but T. bastosi was affected only by the residual effect. Although the herbicide caused a reduction in the number of eggs laid by the females of both pest mites, it is suggested that sublethal effects of glyphosate stimulates oviposition of P. latus and T. bastosi: both species displayed higher reproductive rates when exposed to 0.36 kg ha(-1) of the herbicide. We conclude that glyphosate negatively affects the arthropod herbivores studied and we discuss possible implications on their biological control in Jatropha curcas plantations.

Estimating economic thresholds for site-specific weed control using manual weed counts and sensor technology: an example based on three winter wheat trials.

PubMed

Keller, Martina; Gutjahr, Christoph; Möhring, Jens; Weis, Martin; Sökefeld, Markus; Gerhards, Roland

2014-02-01

Precision experimental design uses the natural heterogeneity of agricultural fields and combines sensor technology with linear mixed models to estimate the effect of weeds, soil properties and herbicide on yield. These estimates can be used to derive economic thresholds. Three field trials are presented using the precision experimental design in winter wheat. Weed densities were determined by manual sampling and bi-spectral cameras, yield and soil properties were mapped. Galium aparine, other broad-leaved weeds and Alopecurus myosuroides reduced yield by 17.5, 1.2 and 12.4 kg ha(-1) plant(-1)  m(2) in one trial. The determined thresholds for site-specific weed control with independently applied herbicides were 4, 48 and 12 plants m(-2), respectively. Spring drought reduced yield effects of weeds considerably in one trial, since water became yield limiting. A negative herbicide effect on the crop was negligible, except in one trial, in which the herbicide mixture tended to reduce yield by 0.6 t ha(-1). Bi-spectral cameras for weed counting were of limited use and still need improvement. Nevertheless, large weed patches were correctly identified. The current paper presents a new approach to conducting field trials and deriving decision rules for weed control in farmers' fields. © 2013 Society of Chemical Industry.

What do farmers' weed control decisions imply about glyphosate resistance? Evidence from surveys of US corn fields.

PubMed

Wechsler, Seth J; McFadden, Jonathan R; Smith, David J

2018-05-01

The first case of glyphosate-resistant weeds in the United States was documented in 1998, 2 years after the commercialization of genetically engineered herbicide-resistant (HR) corn and soybeans. Currently, over 15 glyphosate-resistant weed species affect US crop production areas. These weeds have the potential to reduce yields, increase costs, and lower farm profitability. The objective of our study is to develop a behavioral model of farmers' weed management decisions and use it to analyze weed resistance to glyphosate in US corn farms. On average, we find that weed control increased US corn yields by 3700 kg ha -1 (worth approximately $US 255 ha -1 ) in 2005 and 3500 kg ha -1 (worth approximately $US 575 ha -1 ) in 2010. If glyphosate resistant weeds were absent, glyphosate killed approximately 99% of weeds, on average, when applied at the label rate in HR production systems. Average control was dramatically lower in states where glyphosate resistance was widespread. We find that glyphosate resistance had a significant impact on weed control costs and corn yields of US farmers in 2005 and 2010. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Allelopathic influence of a wheat or rye cover crop on growth and yield of no-till cotton

USDA-ARS?s Scientific Manuscript database

TECHNICAL ABSTRACT No-till planting cotton into small grain cover crops has many benefits including reducing soil erosion and allelopathic suppression of weeds. It is suggested that the potentials of allelopathy on cotton plants. Nevertheless, little is known about the actual effects of alleloche...

EFFECT OF ALTERNATING WETTING AND DRYING IRRIGATION METHODS ON PHOTOSYNTHESIS AND TEMPERATURE OF RICE AND WEED PLANTS.

USDA-ARS?s Scientific Manuscript database

Reduced input systems such as alternating wetting and drying (AWD) and furrow irrigation can potentially reduce water costs and limit the release of greenhouse gases in rice production, but also can introduce unwanted crop stresses that compromise crop yield and quality, as well as introducing compl...

A mowing strategy to convert red clover to annual crops in organic farming

USDA-ARS?s Scientific Manuscript database

Organic producers are interested in no-till cropping systems. In this study, we found that perennial clover can be converted to corn without tillage. Conversion tactics involved fall mowing in the third year of red clover, followed by between-row mowing of weeds and volunteer red clover in corn gr...

First report of dodder (Cuscuta pentagona) on chickpea (Cicer arietinum) in the United States

USDA-ARS?s Scientific Manuscript database

Chickpea (Cicer arietinum L.) is an important rotational and an emerging specialty crop in the Pacific Northwest of the United States, in California, and in the Northern Great Plains of the USA and Canada. Dodders (Cuscuta spp.) are widespread parasitic weeds on many crops worldwide. Several Cusc...

75 FR 32736 - Notice of Solicitation for Members of the National Agricultural Research, Extension, Education...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-09

... Science Society Category G. National Crop, Soil, Agronomy, Horticulture, or Weed Science Society Category... research, crop and animal science, land-grant institutions, non-land grant college or university with a historic commitment to research in the food and agricultural sciences, food retailing and marketing, rural...

The role of plant pathology and plant pathology journals in future food security

USDA-ARS?s Scientific Manuscript database

The world's population is expected to exceed 9 billion by 2050 and this will require a significant increase in crop production for global food security. Future increases in crop production will require limiting the effects of weeds, insects, and diseases incited by fungi, viruses, nematodes, and ba...

Managing cool-season weeds in sugarbeet grown for biofuel in the Southeastern U.S.

USDA-ARS?s Scientific Manuscript database

Sugarbeet, grown for biofuel, is being considered as an alternate cool-season crop in the southeastern U. S. coastal plain. Typically, the crop would be seeded in the autumn, grow through the winter, and harvested the following spring. Labels for herbicides registered for use on sugarbeet grown in ...

Effects of integrated polyethylene and cover crop mulch, conservation tillage, and herbicide application on weed control, yield, and economic returns in watermelon

USDA-ARS?s Scientific Manuscript database

The lack of conservation adoption in watermelon production reflects the lack of field practice recommendations addressing the challenges associated with producing vegetables in minimally disturbed cover crop residues. A three year watermelon experiment was established in fall 2013 to evaluate integr...

Towards a no-till no-spray future? Introduction to a symposium on nonchemical weed management for reduced-tillage cropping systems

USDA-ARS?s Scientific Manuscript database

Reduced-tillage systems including no-tillage and strip tillage have well-known benefits for conserving and improving soils, protecting vulnerable crops from extreme weather events, and reducing labor and fuel costs associated with full-width inversion tillage. Despite these benefits, reduced-tillage...

Study on field weed recognition in real time

NASA Astrophysics Data System (ADS)

He, Yong; Pan, Jiazhi; Zhang, Yun

2006-02-01

This research aimed to identify weeds from crops in early stage in the field by using image-processing technology. As 3CCD images offer greater binary value difference between weed and crop section than ordinary digital images taken by common cameras. It has 3 channels (green, red, ir red), which takes a snap-photo of the same area, and the three images can be composed into one image, which facilitates the segmentation of different areas. In this research, MS3100 3CCD camera is used to get images of 6 kinds of weeds and crops. Part of these images contained more than 2 kinds of plants. The leaves' shapes, sizes and colors may be very similar or differs from each other greatly. Some are sword-shaped and some (are) round. Some are large as palm and some small as peanut. Some are little brown while other is blue or green. Different combinations are taken into consideration. By the application of image-processing toolkit in MATLAB, the different areas in the image can be segmented clearly. The texture of the images was also analyzed. The processing methods include operations, such as edge detection, erosion, dilation and other algorithms to process the edge vectors and textures. It is of great importance to segment, in real time, the different areas in digital images in field. When the technique is applied in precision farming, many energies and herbicides and many other materials can be saved. At present time large scale softwares as MATLAB on PC are also used, but the computation can be reduced and integrated into a small embedded system. The research results have shown that the application of this technique in agricultural engineering is feasible and of great economical value.

Weed control in a native rubber crop (Parthenium argentatum gray)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitworth, J.W.

1978-01-01

There is a renewed interest in the production of rubber from guayule (Parthenium argentatum). Excellent control of several weed species in guayule has been obtained with Varsol (a naphtha oil) at 30-40 gal/acre applied at the cotyledon stage. At this stage, guayule survival averaged 86-63% according to dose, but plants up to 10 days old at the time of treatment showed increasing tolerance. Paraffin was somewhat more selective that Varsol.

Molecular and morphological differentiation between the crop and weedy types in velvetleaf (Abutilon theophrasti Medik.) using a chloroplast DNA marker: seed source of the present invasive velvetleaf in Japan.

PubMed

Kurokawa, S; Shibaike, H; Akiyama, H; Yoshimura, Y

2004-12-01

A comparison of chloroplast DNA (cpDNA) sequences was carried out between the crop and weed types of Abutilon theophrasti to clarify the seed source of the present weedy velvetleaf in Japan. A sequencing analysis of approx. 6% of the chloroplast genome (ca 10 kbp) detected three nucleotide substitutions, one six-base-pair insertion/deletion (indel) and one 30-base pair inversion, which distinguish two haplotypes of cpDNA. A PCR-based survey of the indel and the inversion revealed that the 93 accessions of velvetleaf collected from the world could be divided into two groups. A morphological marker (capsule color) could be used to discriminate the crop type and the weed type, and hence, along with cpDNA haplotype, to distinguish three genotypes (Type I, II, and III). All Japanese cultivars and crop accessions from other countries were Type I. Weed types were divided into Type II and III. All of the samples from the USA, and the samples taken from grain imports to Japan were Type III. Since most of the weedy types distributed in Japan were of Type III, it is argued that they were introduced as seeds in the imported grain. We also found that the Type II plants sporadically occurred in Japan. It is suggested that they originated as hybrids, with indigenous cultivars as the maternal ancestor. Such hybrids must have survived since the cessation of velvetleaf cultivation about a century ago.

Bioherbicides: Current knowledge on weed control mechanism.

PubMed

Radhakrishnan, Ramalingam; Alqarawi, Abdulaziz A; Abd Allah, Elsayed Fathi

2018-04-17

Weed control is a challenging event during crop cultivation. Integrated management, including the application of bioherbicides, is an emerging method for weed control in sustainable agriculture. Plant extracts, allelochemicals and some microbes are utilized as bioherbicides to control weed populations. Bioherbicides based on plants and microbes inhibit the germination and growth of weeds; however,few studies conducted in weed physiology. This review ascribes the current knowledge of the physiological changes in weeds that occur during the exposure to bioherbicides. Plant extracts or metabolites are absorbed by weed seeds, which initiates damage to the cell membrane, DNA, mitosis, amylase activity and other biochemical processes and delays or inhibits seed germination. The growth of weeds is also retarded due to low rates of root-cell division, nutrient uptake, photosynthetic pigment synthesis, and plant growth hormone synthesis, while the productions of reactive oxygen species (ROS) and stress-mediated hormones increase, including irregular antioxidant activity. However, lytic enzymes and toxic substances secreted from microbes degrade the weed seed coat and utilize the endosperm for survival, which inhibits seed germination. The microbes grow through the intercellular spaces to reach the root core, and the deposition of toxins in the cells affects cell division and cellular functions. Some of the metabolites of deleterious microbes cause disease, necrosis and chlorosis,which inhibit the germination and growth of weed seeds by suppressing photosynthesis and gibberellin activities and enhancing ROS, abscisic acid and ethylene. This review explains the effects of bioherbicides (derived from plants and microbes) on weed-plant physiology to elucidate their modes of action. Copyright © 2018 Elsevier Inc. All rights reserved.

Impact of an invasive weed, Parthenium hysterophorus, on a pasture community in south east Queensland, Australia.

PubMed

Nguyen, Thi; Bajwa, Ali Ahsan; Belgeri, Amalia; Navie, Sheldon; O'Donnell, Chris; Adkins, Steve

2017-12-01

Parthenium weed is a highly invasive alien species in more than 40 countries around the world. Along with severe negative effects on human and animal health and crop production, it also causes harm to ecosystem functioning by reducing the native plant species biodiversity. However, its impacts on native plant species, especially in pasture communities, are less known. Given parthenium weed causes substantial losses to Australian pastures' productivity, it is crucial to estimate its impact on pasture communities. This study evaluates the impact of parthenium weed upon species diversity in a pasture community at Kilcoy, south east Queensland, Australia. Sub-sites containing three levels of parthenium weed density (i.e. high, low and zero) were chosen to quantify the above- and below-ground plant community structure. Species richness, diversity and evenness were all found to be significantly reduced as the density of parthenium weed increased; an effect was evident even when parthenium weed was present at relatively low densities (i.e. two plants m -2 ). This trend was observed in the summer season as well as in winter season when this annual weed was absent from the above-ground plant community. This demonstrates the strong impact that parthenium weed has upon the community composition and functioning throughout the year. It also shows the long-term impact of parthenium weed on the soil seed bank where it had displaced several native species. So, management options used for parthenium weed should also consider the reduction of parthenium weed seed bank along with controlling its above-ground populations.

Weed Growth and Efficacy of Pre-Applied Herbicides in Alternative Rooting Substrates Used in Container-Grown Nursery Crops

USDA-ARS?s Scientific Manuscript database

Container-grown nursery crops in the Southeastern United States are typically grown in a rooting substrate comprised primarily of the ground bark of pine trees. However pine bark is becoming less available and more costly due to changes in production and marketed practices within Southeastern pine f...

Evidence for the role of an invasive weed in widespread occurrence of phytoplasmal diseases in diverse vegetable crops: implications from lineage-specific molecular markers

USDA-ARS?s Scientific Manuscript database

During the period from 2011 to 2013, several plant diseases repeatedly occurred in vegetable crops grown in Yuanmou County, Yunnan Province, China. Affected plants included cowpea, sword bean, string bean, tomato, lettuce, and water spinach. The diseased plants exhibited symptoms of witches’-broom...

A clean start to productive orchards and vineyards: recent research on methyl bromide alternatives for perennial crop nurseries

USDA-ARS?s Scientific Manuscript database

Methyl bromide (MB) is an important pest management tool in open field perennial crop nurseries in California for control of many soil borne pests including plant parasitic nematodes, pathogens, and weeds. Because MB is being phased out under the provisions of the Montreal Protocol, alternatives are...

Overcoming weed management challenges in cover crop-based organic rotational no-till soybean production in the Eastern US

USDA-ARS?s Scientific Manuscript database

Cover crop-based, organic rotational no-till soybean production has been gaining traction in the Eastern region of the United States because of the ability of this new system to enhance soil conservation, reduce labor requirements, and decrease diesel fuel use compared to traditional organic product...

Incidence and molecular diversity of poleroviruses infecting cucurbit crops and weed plants in Thailand.

PubMed

Cheewachaiwit, S; Warin, N; Phuangrat, B; Rukpratanporn, S; Gajanandana, O; Balatero, C H; Chatchawankanphanich, O

2017-07-01

Overall, 244 samples of cucurbit crops with yellowing symptoms and selected weed species, from 15 provinces in Thailand, were screened by RT-PCR using primers Polero-CP-F and Polero-CP-R. A total of 160 samples (~66%) were infected by poleroviruses. Analysis of a 1.4 kb region covering the 3' RNA-dependent RNA polymerase (RdRp) gene, the intergenic non-coding region (iNCR), and the coat protein (CP), showed that four poleroviruses, namely, cucurbit aphid-borne yellows virus (CABYV), luffa aphid-borne yellows virus (LABYV), melon aphid-borne yellows virus (MABYV) and suakwa aphid-borne yellows virus (SABYV) were associated with the yellowing symptoms in cucurbit crops. Further analyses indicated presence of putative recombinant viruses referred to as CABYV-R and SABYV-R. CABYV-R was derived from the recombination between MABYV and the common strain of CABYV (CABYV-C). SABYV-R was derived from the recombination of MABYV and SABYV.

Neural networks using broadband spectral discriminators reduces illumination required for broccoli identification in weedy fields

NASA Astrophysics Data System (ADS)

Hahn, Federico

1996-03-01

Statistical discriminative analysis and neural networks were used to prove that crop/weed/soil discrimination by optical reflectance was feasible. The wavelengths selected as inputs on those neural networks were ten nanometers width, reducing the total collected radiation for the sensor. Spectral data collected from several farms having different weed populations were introduced to discriminant analysis. The best discriminant wavelengths were used to build a wavelength histogram which selected the three best spectral broadbands for broccoli/weed/soil discrimination. The broadbands were analyzed using a new single broadband discriminator index named the discriminative integration index, DII, and the DII values obtained were used to train a neural network. This paper introduces the index concept, its results and its use for minimizing artificial lightning requirements with broadband spectral measurements for broccoli/weed/soil discrimination.

Cumulative impact of GM herbicide-tolerant cropping on arable plants assessed through species-based and functional taxonomies.

PubMed

Squire, Geoffrey R; Hawes, Cathy; Begg, Graham S; Young, Mark W

2009-01-01

In a gradualist approach to the introduction of crop biotechnology, the findings of experimentation at one scale are used to predict the outcome of moving to a higher scale of deployment. Movement through scales had occurred for certain genetically modified herbicide-tolerant (GMHT) crops in the UK as far as large-scale field trials. However, the land area occupied by these trials was still <1% of the area occupied by the respective non-GM crops. Some means is needed to predict the direction and size of the effect of increasing the area of GMHT cropping on ecological variables such as the diversity among species and trophic interactions. Species-accumulation curves are examined here as a method of indicating regional-scale impacts on botanical diversity from multiple field experiments. Data were used from experiments on the effect of (GMHT) crops and non-GM, or conventional, comparators in fields sown with four crop types (beet, maize, spring and winter oilseed rape) at a total of 250 sites in the UK between 2000 and 2003. Indices of biodiversity were measured in a split-field design comparing GMHT with the farmers' usual weed management. In the original analyses based on the means at site level, effects were detected on the mass of weeds in the three spring crops and the proportion of broadleaf and grass weeds in winter oilseed rape, but not on indices of plant species diversity. To explore the links between site means and total taxa, accumulation curves were constructed based on the number of plant species (a pool of around 250 species in total) and the number of plant functional types (24), inferred from the general life-history characteristics of a species. Species accumulation differed between GMHT and conventional treatments in direction and size, depending on the type of crop and its conventional management. Differences were mostly in the asymptote of the curve, indicative of the maximum number of species found in a treatment, rather than the steepness of the curve. In winter oilseed rape, 8% more species were accumulated in the GMHT treatment, mainly as a result of the encouragement of grass species by the herbicide when applied in the autumn. (Overall, GMHT winter oilseed rape had strong negative effects on both the food web and the potential weed burden by increasing the biomass of grasses and decreasing that of broadleaf weeds.) In maize, 33% more species-a substantial increase-were accumulated in the GMHT than in the conventional, consistent with the latter's highly suppressive weed management using triazine herbicides. In the spring oilseed rape and beet, fewer species (around 10%) were accumulated in the GMHT than the conventional. The GMHT treatments did not remove or add any functional (life history) types, however. Differences in species accumulation between treatments appeared to be caused by loss or gain of rarer species. The generality of this effect was confirmed by simulations of species accumulation in which the species complement at each of 50 sites was drawn from a regional pool and subjected to reducing treatment at each site. Shifts in the species-accumulation parameters, comparable to those measured, occurred only when a treatment removed the rarer species at each site. Species accumulation provided a set of simple curve-parameters that captured the net result of numerous local effects of treatments on plant species and, in some instances, the balance between grass and broadleaf types. The direction of effect was not the same in the four crops and depended on the severity of the conventional treatment and on complex interactions between season, herbicide and crop. The accumulation curves gave an indication of potential positive or negative consequences for regional species pools of replacing a conventional practice with GMHT weed management. In this and related studies, a range of indicators, through which diversity was assessed by both species and functional type, and at both site and regional scales, gave more insight into effects of GMHT treatment than provided by any one indicator. Species accumulation was shown to discriminate at the regional scale between agronomic treatments that had little effect on species number at the field scale. While a comprehensive assessment of GM cropping needs to include an examination of regional effects, as here, the costs of doing this in all instances would be prohibitive. Simulations of diversity-reducing treatments could provide a theoretical framework for predicting the likely regional effects from in-field plant dynamics. Accumulation curves potentially offer a means of linking within-site effects to regional impacts on biodiversity resulting from any change in agricultural practice. To guide empirical measurement, there is a scope to apply a methodology such as individual-based modelling at the field scale to explore the links between agronomic treatments and the relative abundance of plant types. The framework needs to be validated in practice, using species-based and functional taxonomies, the latter defined by measured rather than inferred traits.

A review of aquatic weed biology and management research conducted by the United States Department of Agriculture-Agricultural Research Service.

PubMed

Anderson, Lars W J

2003-01-01

Ever-increasing demand for water to irrigate crops, support aquaculture, provide domestic water needs and to protect natural aquatic and riparian habitats has necessitated research to reduce impacts from a parallel increase in invasive aquatic weeds. This paper reviews the past 4-5 years of research by USDA-ARS covering such areas as weed biology, ecology, physiology and management strategies, including herbicides, biological control and potential for use of natural products. Research approaches range from field-level studies to highly specific molecular and biochemical work, spanning several disciplines and encompassing the most problematic weeds in these systems. This research has led to new insights into plant competition, host-specificity, and the fate of aquatic herbicides, their modes of action and effects on the environment. Another hallmark of USDA-ARS research has been its many collaborations with other federal, state action and regulatory agencies and private industry to develop new solutions to aquatic weed problems that affect our public natural resources and commercial enterprises.

[Use of Remote Sensing for Crop and Soil Analysis

NASA Technical Reports Server (NTRS)

Johannsen, Chris J.

1997-01-01

The primary agricultural objective of this research is to determine what soil and crop information can be verified from remotely sensed images during the growing season. Specifically: (1) Elements of crop stress due to drought, weeds, disease and nutrient deficiencies will be documented with ground truth over specific agricultural sites and (2) Use of remote sensing with GPS and GIS technology for providing a safe and environmentally friendly application of fertilizers and chemicals will be documented.

Environmental impacts of conversion of cropland to biomass production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, T.H.; Brown, G.F.; Bingham, L.

1996-12-31

A study was initiated to determine the effects of conversion of row crop land to biomass production on runoff quality and quantity. Treatments were: (1) remain in row crop (no-till corn); (2) convert to short rotation woody crop (SRWC) production with sweetgum (Liquidambar styraciflua L.) planted in a 1.5 in by 3 in spacing maintaining complete weed control; (3) convert to SRWC with a tall fescue (Festuca eliator L.) cover crop planted in a 2.4 in strip centered between rows of trees to reduce erosion; and (4) convert to switchgrass (Panicum virgatum L.) as a biomass energy crop. Plots withinmore » a block similar in size (approximately 0.45 ha in block 1 and 0.20 ha in block 2), slope, soils, topographic position, recent land use history, etc. Although switchgrass plots eroded more early in the growing season, erosion was low once it became well established. Conversely, plots where trees were grown with no cover continued to erode throughout the growing season. These results indicate that growing short-rotation intensively cultured hardwoods with complete weed control will provide little erosion relief in agricultural fields, at least during the first growing season. Planting switchgrass for bioenergy production, however, does protect the soil. Nutrient runoff was related to fertilization.« less

Strategies for management of Sicyos polyacanthus Cogn. (Cucurbitaceae) in sugarcane crops of Tucumán, Argentina.

PubMed

Chaila, Salvador; Arévalo, Roberto A; Piscitelli, Francisco R; Gómez, Raúl Aguero; Sobrero, María T

2005-01-01

Sicyos polyacanthus is one of the most important weed in sugarcane crops of Tucumán (Argentina). The objective of this work was to establish strategies that would decrease the weed incidence in the crop to a minimum level. The study was carried out during 1998--2003 at five localities of sugarcane production of Tucumán (Argentina). The plots were 20 m long (192 m2) with 6 furrows and each plot was replicated five times. Treatments were: (i) Mechanical-chemical cultivation without fire; (ii) Mechanical-chemical culltivation with fire; (iii) Mechanical cultivation with handle pulled and with fire; (iv) Mechanical cultivation with handle pulled without fire; (v) Mechanical and chemical variants with fertilization and without fertilization; (vi) Mechanical and chemical variants with watering and without watering; (vii) Fallow and rotation, at the sugarcane crop renovation; (viii) Mechanical and chemical variants for plant cane and ratoon cane; and (ix) Mulching of harvest rests. The results suggest that besides the use of preemergent herbicides, fire marks the entry point of control, influencing fluxes and seed viability. It appears that fallow, mulching, and rotation of crops is fundamental for eliminating seeds that live short time in the soil and increase the mortality rate of species.

Ecologically sustainable weed management: How do we get from proof-of-concept to adoption?

PubMed

Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne; Childs, Dylan; Christensen, Svend; Cousens, Roger; Eizenberg, Hanan; Heijting, Sanne; Loddo, Donato; Merotto, Aldo; Renton, Michael; Riemens, Marleen

2016-07-01

Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and greater weed impacts due to changes in climate and land use. Broad-scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management strategies with multiple complementary tactics, developing crop genotypes for enhanced weed suppression, and tailoring management strategies to better accommodate variability in weed spatial distributions. In all three cases, proof-of-concept has long been demonstrated and considerable scientific innovations have been made, but uptake by farmers and land managers has been extremely limited. Impediments to employing these and other ecologically based approaches include inadequate or inappropriate government policy instruments, a lack of market mechanisms, and a paucity of social infrastructure with which to influence learning, decision-making, and actions by farmers and land managers. We offer examples of how these impediments are being addressed in different parts of the world, but note that there is no clear formula for determining which sets of policies, market mechanisms, and educational activities will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming systems and land management units. © 2016 by the Ecological Society of America.

Model Forecasts of Atrazine in Lake Michigan in Response to Various Sensitivity and Potential Management Scenarios

EPA Science Inventory

For more than forty years, the herbicide atrazine has been used on corn crops in the Lake Michigan basin to control weeds. It is usually applied to farm fields in the spring before or after the corn crop emerges. A version of the WASP4 mass balance model, LM2-Atrazine, was used...

Suitability of Southern Pines, Other Selected Crops, and Nutsedge to a Longidorus sp. Associated with Stunting of Loblolly Pine Seedlings

Treesearch

S.W. Fraedrich; M.M. Cram; Z.A. Handoo

2003-01-01

An undescribed needle nematode (Longidorus sp.) has been associated with severely stunted loblolly pine seedlings at a south Georgia nursery. Containers with selected crop and weed species were infested with 100 or 200 adults and juveniles of the Longidorus individuals to evaluate host suitability. Nematode populations increased in...

Impact of Land Management Practices on Carabids (Coleoptera: Carabidae) and Other Arthropods on the Western High Plains of North America

USDA-ARS?s Scientific Manuscript database

This work was done in plots that had been subjected to three successive years of an agronomic experiment that evaluated the effects of a wheat cover crop or no cover crop on weed and water management. After the third growing season, pitfall traps were installed and arthropods were collected and iden...

A Meta-Analysis of the Impact of Anaerobic Soil Disinfestation on Pest Suppression and Yield of Horticultural Crops

PubMed Central

Shrestha, Utsala; Augé, Robert M.; Butler, David M.

2016-01-01

Anaerobic soil disinfestation (ASD) is a proven but relatively new strategy to control soil borne pests of horticultural crops through anaerobic decomposition of organic soil amendments. The ASD technique has primarily been used to control soil borne pathogens; however, this technique has also shown potential to control plant parasitic nematodes and weeds. ASD can utilize a broad range of carbon (C) amendments and optimization may improve efficacy across environments. In this context, a meta-analysis using a random-effects model was conducted to determine effect sizes of the ASD effect on soil borne pathogens (533 studies), plant parasitic nematodes (91 studies), and weeds (88 studies) compared with unamended controls. Yield response to ASD was evaluated (123 studies) compared to unamended and fumigated controls. We also examined moderator variables for environmental conditions and amendments to explore the impact of these moderators on ASD effectiveness on pests and yield. Across all pathogen types with the exception of Sclerotinia spp., ASD studies show suppression of bacterial, oomycete and fungal pathogens (59 to 94%). Pathogen suppression was effective under all environmental conditions (50 to 94%) and amendment types (53 to 97%), except when amendments were applied at rates less than 0.3 kg m-2. The ASD effect ranged from 15 to 56% for nematode suppression and 32 to 81% for weed suppression, but these differences were not significant. Significant nematode moderators included study type, soil type, sampling depth, incubation period, and use of mixed amendments. Weed suppression due to ASD showed significant heterogeneity for all environmental conditions, confirming that these studies do not share a common effect size. Total crop yield was not reduced by ASD when compared to a fumigant control and yield was significantly higher (30%) compared to an unamended control, suggesting ASD as a feasible option to maintain yield without chemical soil fumigants. We conclude ASD is effective against soil borne pathogens and while not conclusive due to a limited number of studies, we expect the same for nematodes and weeds given observed effect sizes. Findings should assist researchers in exploring ASD efficacy in particular environmental conditions and allow for development of standard treatment protocols. PMID:27617017

Optical Sensing to Determine Tomato Plant Spacing for Precise Agrochemical Application: Two Scenarios

PubMed Central

Martínez-Guanter, Jorge; Garrido-Izard, Miguel; Valero, Constantino; Slaughter, David C.; Pérez-Ruiz, Manuel

2017-01-01

The feasibility of automated individual crop plant care in vegetable crop fields has increased, resulting in improved efficiency and economic benefits. A systems-based approach is a key feature in the engineering design of mechanization that incorporates precision sensing techniques. The objective of this study was to design new sensing capabilities to measure crop plant spacing under different test conditions (California, USA and Andalucía, Spain). For this study, three different types of optical sensors were used: an optical light-beam sensor (880 nm), a Light Detection and Ranging (LiDAR) sensor (905 nm), and an RGB camera. Field trials were conducted on newly transplanted tomato plants, using an encoder as a local reference system. Test results achieved a 98% accuracy in detection using light-beam sensors while a 96% accuracy on plant detections was achieved in the best of replications using LiDAR. These results can contribute to the decision-making regarding the use of these sensors by machinery manufacturers. This could lead to an advance in the physical or chemical weed control on row crops, allowing significant reductions or even elimination of hand-weeding tasks. PMID:28492504

Interactions of tillage and cover crop on water, sediment, and pre-emergence herbicide loss in glyphosate-resistant cotton: implications for the control of glyphosate-resistant weed biotypes.

PubMed

Krutz, L Jason; Locke, Martin A; Steinriede, R Wade

2009-01-01

The need to control glyphosate [N-(phosphonomethyl)glycine]-resistant weed biotypes with tillage and preemergence herbicides in glyphosate-resistant crops (GRCs) is causing a reduction in no-tillage hectarage thereby threatening the advances made in water quality over the past decade. Consequently, if environmental gains afforded by GRCs are to be maintained, then an in-field best management practice (BMP) compatible with tillage is required for hectarage infested with glyphosate-resistant weed biotypes. Thus, 1 d after a preemergent application of fluometuron [N,N-dimethyl-N'-(3-(trifluoromethyl)phenyl)urea] (1.02 kg ha(-1)) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] (1.18 kg ha(-1)) to a Dundee silt loam (fine-silty, mixed, active, thermic Typic Endoaqualf), simulated rainfall (60 mm h(-1)) was applied to 0.0002-ha microplots for approximately 1.25 h to elucidate tillage (no tillage [NT] and reduced tillage [RT])and cover crop (no cover [NC] and rye cover [RC]) effects on water, sediment, and herbicide loss in surface runoff. Regardless of tillage, RC delayed time-to-runoff 1.3-fold, reduced cumulative runoff volume 1.4-fold, and decreased cumulative sediment loss 4.7-fold. Cumulative fluometuron loss was not affected by tillage or cover crop. Conversely, total metolachlor loss was 1.3-fold lower in NT than RT and 1.4-fold lower in RC than NC. These data indicate that RC can be established in hectarage requiring tillage and potentially curtail water, sediment, and preemergence herbicide losses in the spring to levels equivalent to or better than that of NT, thereby protecting environmental gains provided by GRCs.

Yield of glyphosate-resistant sugar beets and efficiency of weed management systems with glyphosate and conventional herbicides under German and Polish crop production.

PubMed

Nichterlein, Henrike; Matzk, Anja; Kordas, Leszek; Kraus, Josef; Stibbe, Carsten

2013-08-01

In sugar beet production, weed control is one of the most important and most expensive practices to ensure yield. Since glyphosate-resistant sugar beets are not yet approved for cultivation in the EU, little commercial experience exists with these sugar beets in Europe. Experimental field trials were conducted at five environments (Germany, Poland, 2010, 2011) to compare the effects of glyphosate with the effects of conventional weed control programs on the development of weeds, weed control efficiency and yield. The results show that the glyphosate weed control programs compared to the conventional methods decreased not only the number of herbicide applications but equally in magnitude decreased the dosage of active ingredients. The results also showed effective weed control with glyphosate when the weed covering was greater and sugar beets had a later growth stage of four true leaves. Glyphosate-resistant sugar beets applied with the glyphosate herbicide two or three times had an increase in white sugar yield from 4 to 18 % in comparison to the high dosage conventional herbicide systems. In summary, under glyphosate management sugar beets can positively contribute to the increasingly demanding requirements regarding efficient sugar beet cultivation and to the demands by society and politics to reduce the use of chemical plant protection products in the environment.

Weeds and ground-dwelling predators′ response to two different weed management systems in glyphosate-tolerant cotton: A farm-scale study

PubMed Central

Farinós, Gema P.; Gómez, Pablo; Gutiérrez, Elena; Sánchez, Francisco Javier; Escorial, María Concepción; Ortego, Félix; Chueca, María Cristina; Castañera, Pedro

2018-01-01

The use of glyphosate, as a post-emergence broad-spectrum herbicide in genetically modified glyphosate-tolerant (GT) cotton, supposes a big change in weed management programs with respect to a conventional regime. Thus, alterations in arable flora and arthropod fauna must be considered when evaluating their potential impacts. A 3-year farm-scale study was conducted in a 2-ha GT cotton crop, in southern Spain, to compare the effects of conventional and glyphosate herbicide regimes on weed abundance and diversity and their consequences for ground-dwelling predators. Surveys reveal that weed density was relatively low within all treatments with a few dominant species, with significantly higher weed densities and modifications of the floristic composition in glyphosate-treated plots that led to an increase in the abundance of Portulaca oleracea and to a reduction in plant diversity. The activity-density of the main predatory arthropod taxa (spiders, ground beetles, rove beetles and earwigs) varied among years, but no significant differences were obtained between conventional and glyphosate herbicide regimes. However, significant differences between treatments were obtained for ground beetles species richness and diversity, being higher under the glyphosate herbicide regime, and a positive correlation with weed density could be established for both parameters. The implications of these findings to weed control in GT cotton are discussed. PMID:29351549

Weeds and ground-dwelling predators' response to two different weed management systems in glyphosate-tolerant cotton: A farm-scale study.

PubMed

García-Ruiz, Esteban; Loureiro, Íñigo; Farinós, Gema P; Gómez, Pablo; Gutiérrez, Elena; Sánchez, Francisco Javier; Escorial, María Concepción; Ortego, Félix; Chueca, María Cristina; Castañera, Pedro

2018-01-01

The use of glyphosate, as a post-emergence broad-spectrum herbicide in genetically modified glyphosate-tolerant (GT) cotton, supposes a big change in weed management programs with respect to a conventional regime. Thus, alterations in arable flora and arthropod fauna must be considered when evaluating their potential impacts. A 3-year farm-scale study was conducted in a 2-ha GT cotton crop, in southern Spain, to compare the effects of conventional and glyphosate herbicide regimes on weed abundance and diversity and their consequences for ground-dwelling predators. Surveys reveal that weed density was relatively low within all treatments with a few dominant species, with significantly higher weed densities and modifications of the floristic composition in glyphosate-treated plots that led to an increase in the abundance of Portulaca oleracea and to a reduction in plant diversity. The activity-density of the main predatory arthropod taxa (spiders, ground beetles, rove beetles and earwigs) varied among years, but no significant differences were obtained between conventional and glyphosate herbicide regimes. However, significant differences between treatments were obtained for ground beetles species richness and diversity, being higher under the glyphosate herbicide regime, and a positive correlation with weed density could be established for both parameters. The implications of these findings to weed control in GT cotton are discussed.

Plant sciences. Will GM rapeseed cut the mustard?

PubMed

Heritage, John

2003-10-17

Genetic modification can render crops resistant to herbicides, providing them with a growth advantage so that they can outcompete weeds. However, there are concerns about the possibility that transgenes could flow from GM crops into wild plant populations. In his Perspective, Heritage discusses these important issues in terms of a new report (Wilkinson et al.) that provides a nationwide assessment in the UK of the ability of the conventional crop, oilseed rape (Brassica napus), to form hybrids with its wild relatives.

The history and current status of glyphosate.

PubMed

Duke, Stephen O

2018-05-01

Glyphosate is the only herbicide to target the enzyme 5-enolpyruvyl-3-shikimate phosphate synthase (EPSPS). It is a high use rate, non-selective herbicide that translocates primarily to metabolic sinks, killing meristematic tissues away from the application site. Its phloem-mobile properties and slow action in killing weeds allow the herbicide to move throughout the plant to kill all meristems, making it effective for perennial weed control. Since commercialization in 1974, its use has grown to dominate the herbicide market. Much of its use is on transgenic, glyphosate-resistant crops (GRCs), which have been the dominant transgenic crops worldwide. GRCs with glyphosate provided the most effective and inexpensive weed management technology in history for a decade or more. However, as a consequence of the rapid increase in glyphosate-resistant (GR) weeds, the effectiveness of glyphosate use in GRCs is declining. Critics have claimed that glyphosate-treated GRCs have altered mineral nutrition and increased susceptibility to plant pathogens because of glyphosate's ability to chelate divalent metal cations, but the complete resistance of GRCs to glyphosate indicates that chelating metal cations do not contribute to the herbicidal activity or significantly affect mineral nutrition. The rates of increases in yields of maize, soybean, and cotton in the USA have been unchanged after high adoption rates of GRCs. Glyphosate is toxic to some plant pathogens, and thereby can act as a fungicide in GRCs. Ultra-low doses of glyphosate stimulate plant growth in glyphosate-susceptible plants by unknown mechanisms. Despite rapid and widespread increases in GR weeds, glyphosate use has not decreased. However, as GR weeds increase, adoption of alternative technologies will eventually lead to decreased use. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Controlling weeds with fungi, bacteria and viruses: a review

PubMed Central

Harding, Dylan P.; Raizada, Manish N.

2015-01-01

Weeds are a nuisance in a variety of land uses. The increasing prevalence of both herbicide resistant weeds and bans on cosmetic pesticide use has created a strong impetus to develop novel strategies for controlling weeds. The application of bacteria, fungi and viruses to achieving this goal has received increasingly great attention over the last three decades. Proposed benefits to this strategy include reduced environmental impact, increased target specificity, reduced development costs compared to conventional herbicides and the identification of novel herbicidal mechanisms. This review focuses on examples from North America. Among fungi, the prominent genera to receive attention as bioherbicide candidates include Colletotrichum, Phoma, and Sclerotinia. Among bacteria, Xanthomonas and Pseudomonas share this distinction. The available reports on the application of viruses to controlling weeds are also reviewed. Focus is given to the phytotoxic mechanisms associated with bioherbicide candidates. Achieving consistent suppression of weeds in field conditions is a common challenge to this control strategy, as the efficacy of a bioherbicide candidate is generally more sensitive to environmental variation than a conventional herbicide. Common themes and lessons emerging from the available literature in regard to this challenge are presented. Additionally, future directions for this crop protection strategy are suggested. PMID:26379687

Crop production management: Organic wheat and small grains

USDA-ARS?s Scientific Manuscript database

Key management practices for organic wheat and small grain production are provided, including variety selection, planting date, seeding rate, drill calibration and operation, soil fertility, and management of weeds, insect pests, and diseases. ...

4-Hydroxyphenylpyruvate Dioxygenase Inhibitors: From Chemical Biology to Agrochemicals.

PubMed

Ndikuryayo, Ferdinand; Moosavi, Behrooz; Yang, Wen-Chao; Yang, Guang-Fu

2017-10-04

The development of new herbicides is receiving considerable attention to control weed biotypes resistant to current herbicides. Consequently, new enzymes are always desired as targets for herbicide discovery. 4-Hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) is an enzyme engaged in photosynthetic activity and catalyzes the transformation of 4-hydroxyphenylpyruvic acid (HPPA) into homogentisic acid (HGA). HPPD inhibitors constitute a promising area of discovery and development of innovative herbicides with some advantages, including excellent crop selectivity, low application rates, and broad-spectrum weed control. HPPD inhibitors have been investigated for agrochemical interests, and some of them have already been commercialized as herbicides. In this review, we mainly focus on the chemical biology of HPPD, discovery of new potential inhibitors, and strategies for engineering transgenic crops resistant to current HPPD-inhibiting herbicides. The conclusion raises some relevant gaps for future research directions.

Fluridone: a combination germination stimulant and herbicide for problem fields?

PubMed

Goggin, Danica E; Powles, Stephen B

2014-09-01

Problem weeds in agriculture, such as Lolium rigidum Gaud., owe some of their success to their large and dormant seed banks, which permit germination throughout a crop-growing season. Dormant weed seed banks could be greatly depleted by application of a chemical that stimulates early-season germination and then kills the young seedlings. Fluridone, a phytoene desaturase-inhibiting herbicide that can also break seed dormancy, was assessed for its efficacy in this regard. The germination of fluridone-treated Lolium rigidum seeds was stimulated on soils with low organic matter, and almost 100% seedling mortality was observed, while the treatment was only moderately effective on a high-organic-matter potting mix. Seedlings from wheat, canola, common bean and chickpea seeds sown on fluridone-treated sandy loam were bleached and did not survive, but lupins and field peas grew normally. This proof-of-concept study with fluridone suggests that it may be possible to design safe and effective molecules that act as germination stimulants plus herbicides in a range of crop and soil types: a potentially novel way of utilising herbicides to stimulate seed bank germination and a valuable addition to an integrated weed management system. © 2014 Society of Chemical Industry.

Weed vegetation ecology of arable land in Salalah, Southern Oman.

PubMed

El-Sheikh, Mohamed A

2013-07-01

This paper applies multivariate statistical methods to a data set of weed relevés from arable fields in two different habitat types of coastal and mountainous escarpments in Southern Oman. The objectives were to test the effect of environmental gradients, crop plants and time on weed species composition, to rank the importance of these particular factors, and to describe the patterns of species composition and diversity associated with these factors. Through the application of TWINSPAN, DCA and CCA programs on data relating to 102 species recorded in 28 plots and farms distributed in the study area, six plant communities were identified: I- Dichanthium micranthum, II- Cynodon dactylon-D. micranthum, III- Convolvulus arvensis, IV- C. dactylon-Sonchus oleraceus, V- Amaranthus viridis and VI- Suaeda aegyptiaca-Achyranthes aspera. The ordination process (CCA) provided a sequence of plant communities and species diversity that correlated with some anthropogenic factors, physiographic variables and crop types. Therefore, length of time since farm construction, disturbance levels and altitude are the most important factors related to the occurrence of the species. The perennial species correlated with the more degraded mountain areas of new farm stands, whereas most of the annuals correlated with old lowland and less disturbed farms.

Weed vegetation ecology of arable land in Salalah, Southern Oman

PubMed Central

El-Sheikh, Mohamed A.

2013-01-01

This paper applies multivariate statistical methods to a data set of weed relevés from arable fields in two different habitat types of coastal and mountainous escarpments in Southern Oman. The objectives were to test the effect of environmental gradients, crop plants and time on weed species composition, to rank the importance of these particular factors, and to describe the patterns of species composition and diversity associated with these factors. Through the application of TWINSPAN, DCA and CCA programs on data relating to 102 species recorded in 28 plots and farms distributed in the study area, six plant communities were identified: I- Dichanthium micranthum, II- Cynodon dactylon–D. micranthum, III- Convolvulus arvensis, IV- C. dactylon–Sonchus oleraceus, V- Amaranthus viridis and VI- Suaeda aegyptiaca–Achyranthes aspera. The ordination process (CCA) provided a sequence of plant communities and species diversity that correlated with some anthropogenic factors, physiographic variables and crop types. Therefore, length of time since farm construction, disturbance levels and altitude are the most important factors related to the occurrence of the species. The perennial species correlated with the more degraded mountain areas of new farm stands, whereas most of the annuals correlated with old lowland and less disturbed farms. PMID:23961246

What are Soil Fumigants?

EPA Pesticide Factsheets

These pesticides, when applied to soil, form a gas to control pests including nematodes, fungi, bacteria, insects, and weeds, that live in the soil and can disrupt plant growth and crop production. Required safety measures reduce exposure risks.

Registration of Dicamba for Use on Genetically Engineered Crops

EPA Pesticide Factsheets

EPA has registered a new dicamba formulation, Extendimax™ with VaporGrip™, specifically designed to have lower volatility, to control weeds in cotton and soybean plants that have been genetically engineered (GE) to resist dicamba.

Plant growth promoting potential of bacteria isolated on N free media from rhizosphere of Cassia occidentalis.

PubMed

Arun, B; Gopinath, B; Sharma, Shilpi

2012-09-01

Plant growth promoting rhizobacteria (PGPR) are an attractive eco-friendly alternative to chemicals in agriculture. While the rhizospheres of crop plants have been well studied with the objective of screening PGPR, weeds, which play an important role in maintaining ecological balance, have largely been ignored. The rhizosphere of a luxuriantly growing, medicinal weed, Cassia occidentalis was analysed by enumerating PGPR on N free media from the most diverse stage of plant (determined by profiles obtained on denaturing gradient gel electrophoresis). Each isolate was tested for other plant growth promotion assays including production of cellulase, indole acetic acid (IAA), ammonia, HCN, siderophore and chitinase to select for ones possessing multi-trait plant growth promoting (PGP) properties. Selected isolates were used for bacterization of Vigna radiata and Vigna mungo to evaluate their efficacy in promoting plant's growth in seedling germination and axenic pot conditions. Thirty five isolates were analysed further for the array of PGP properties they exhibit. A total of 6 isolates were shortlisted on the basis of maximum traits positive, amount of phosphate solubilized and IAA produced. V. radiata responded well to seed bacterization during seedling germination. A maximum increase of approximately 36 and 60 % was observed for shoot and root length, respectively in V. radiata in axenic pot culture over control plants. Extensive branching of roots was also observed with isolate NL, which produced the maximum amount of IAA. Present study investigated the plant growth promoting isolates obtained on N free media in the rhizosphere of C. occidentalis, which have the potential to be used as inoculants for other crops. This provides a new dimension to the significance of weeds in agricultural ecosystems. The study opens up possibilities for utilization of this property of weeds in plant growth promotion, and subsequent enhancement of yield for agricultural crops.

Cropping system diversification for food production in Mindanao rubber plantations: a rice cultivar mixture and rice intercropped with mungbean

PubMed Central

Elazegui, Francisco; Duque, Jo-Anne Lynne Joy E.; Mundt, Christopher C.; Vera Cruz, Casiana M.

2017-01-01

Including food production in non-food systems, such as rubber plantations and biofuel or bioenergy crops, may contribute to household food security. We evaluated the potential for planting rice, mungbean, rice cultivar mixtures, and rice intercropped with mungbean in young rubber plantations in experiments in the Arakan Valley of Mindanao in the Philippines. Rice mixtures consisted of two- or three-row strips of cultivar Dinorado, a cultivar with higher value but lower yield, and high-yielding cultivar UPL Ri-5. Rice and mungbean intercropping treatments consisted of different combinations of two- or three-row strips of rice and mungbean. We used generalized linear mixed models to evaluate the yield of each crop alone and in the mixture or intercropping treatments. We also evaluated a land equivalent ratio for yield, along with weed biomass (where Ageratum conyzoides was particularly abundant), the severity of disease caused by Magnaporthe oryzae and Cochliobolus miyabeanus, and rice bug (Leptocorisa acuta) abundance. We analyzed the yield ranking of each cropping system across site-year combinations to determine mean relative performance and yield stability. When weighted by their relative economic value, UPL Ri-5 had the highest mean performance, but with decreasing performance in low-yielding environments. A rice and mungbean intercropping system had the second highest performance, tied with high-value Dinorado but without decreasing relative performance in low-yielding environments. Rice and mungbean intercropped with rubber have been adopted by farmers in the Arakan Valley. PMID:28194318

Weed management practices affect the diversity and relative abundance of physic nut mites.

PubMed

Saraiva, Althiéris de Sousa; Sarmento, Renato A; Erasmo, Eduardo A L; Pedro-Neto, Marçal; de Souza, Danival José; Teodoro, Adenir V; Silva, Daniella G

2015-03-01

Crop management practices determine weed community, which in turn may influence patterns of diversity and abundance of associated arthropods. This study aimed to evaluate whether local weed management practices influence the diversity and relative abundance of phytophagous and predatory mites, as well as mites with undefined feeding habits--of the families Oribatidae and Acaridae--in a physic nut (Jatropha curcas L.) plantation subjected to (1) within-row herbicide spraying and between-row mowing; (2) within-row herbicide spraying and no between-row mowing; (3) within-row weeding and between-row mowing; (4) within-row weeding and no between-row mowing; and (5) unmanaged (control). The herbicide used was glyphosate. Herbicide treatments resulted in higher diversity and relative abundance of predatory mites and mites with undefined feeding habit on physic nut shrubs. This was probably due to the toxic effects of the herbicide on mites or to removal of weeds. Within-row herbicide spraying combined with between-row mowing was the treatment that most contributed to this effect. Our results show that within-row weeds harbor important species of predatory mites and mites with undefined feeding habit. However, the dynamics of such mites in the system can be changed according to the weed management practice applied. Among the predatory mites of the family Phytoseiidae Amblydromalus sp. was the most abundant, whereas Brevipalpus phoenicis was the most frequent phytophagous mite and an unidentified oribatid species was the most frequent mite with undefined feeding habit.

Measuring Rates of Herbicide Metabolism in Dicot Weeds with an Excised Leaf Assay.

PubMed

Ma, Rong; Skelton, Joshua J; Riechers, Dean E

2015-09-07

In order to isolate and accurately determine rates of herbicide metabolism in an obligate-outcrossing dicot weed, waterhemp (Amaranthus tuberculatus), we developed an excised leaf assay combined with a vegetative cloning strategy to normalize herbicide uptake and remove translocation as contributing factors in herbicide-resistant (R) and -sensitive (S) waterhemp populations. Biokinetic analyses of organic pesticides in plants typically include the determination of uptake, translocation (delivery to the target site), metabolic fate, and interactions with the target site. Herbicide metabolism is an important parameter to measure in herbicide-resistant weeds and herbicide-tolerant crops, and is typically accomplished with whole-plant tests using radiolabeled herbicides. However, one difficulty with interpreting biokinetic parameters derived from whole-plant methods is that translocation is often affected by rates of herbicide metabolism, since polar metabolites are usually not mobile within the plant following herbicide detoxification reactions. Advantages of the protocol described in this manuscript include reproducible, accurate, and rapid determination of herbicide degradation rates in R and S populations, a substantial decrease in the amount of radiolabeled herbicide consumed, a large reduction in radiolabeled plant materials requiring further handling and disposal, and the ability to perform radiolabeled herbicide experiments in the lab or growth chamber instead of a greenhouse. As herbicide resistance continues to develop and spread in dicot weed populations worldwide, the excised leaf assay method developed and described herein will provide an invaluable technique for investigating non-target site-based resistance due to enhanced rates of herbicide metabolism and detoxification.

Shared and host-specific microbiome diversity and functioning of grapevine and accompanying weed plants.

PubMed

Samad, Abdul; Trognitz, Friederike; Compant, Stéphane; Antonielli, Livio; Sessitsch, Angela

2017-04-01

Weeds and crop plants select their microbiota from the same pool of soil microorganisms, however, the ecology of weed microbiomes is poorly understood. We analysed the microbiomes associated with roots and rhizospheres of grapevine and four weed species (Lamium amplexicaule L., Veronica arvensis L., Lepidium draba L. and Stellaria media L.) growing in proximity in the same vineyard using 16S rRNA gene sequencing. We also isolated and characterized 500 rhizobacteria and root endophytes from L. draba and grapevine. Microbiome data analysis revealed that all plants hosted significantly different microbiomes in the rhizosphere as well as in root compartment, however, differences were more pronounced in the root compartment. The shared microbiome of grapevine and the four weed species contained 145 OTUs (54.2%) in the rhizosphere, but only nine OTUs (13.2%) in the root compartment. Seven OTUs (12.3%) were shared in all plants and compartments. Approximately 56% of the major OTUs (>1%) showed more than 98% identity to bacteria isolated in this study. Moreover, weed-associated bacteria generally showed a higher species richness in the rhizosphere, whereas the root-associated bacteria were more diverse in the perennial plants grapevine and L. draba. Overall, weed isolates showed more plant growth-promoting characteristics compared with grapevine isolates. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Metabolism-Based Herbicide Resistance and Cross-Resistance in Crop Weeds: A Threat to Herbicide Sustainability and Global Crop Production1

PubMed Central

Yu, Qin; Powles, Stephen

2014-01-01

Weedy plant species that have evolved resistance to herbicides due to enhanced metabolic capacity to detoxify herbicides (metabolic resistance) are a major issue. Metabolic herbicide resistance in weedy plant species first became evident in the 1980s in Australia (in Lolium rigidum) and the United Kingdom (in Alopecurus myosuroides) and is now increasingly recognized in several crop-weed species as a looming threat to herbicide sustainability and thus world crop production. Metabolic resistance often confers resistance to herbicides of different chemical groups and sites of action and can extend to new herbicide(s). Cytochrome P450 monooxygenase, glycosyl transferase, and glutathione S-transferase are often implicated in herbicide metabolic resistance. However, precise biochemical and molecular genetic elucidation of metabolic resistance had been stalled until recently. Complex cytochrome P450 superfamilies, high genetic diversity in metabolic resistant weedy plant species (especially cross-pollinated species), and the complexity of genetic control of metabolic resistance have all been barriers to advances in understanding metabolic herbicide resistance. However, next-generation sequencing technologies and transcriptome-wide gene expression profiling are now revealing the genes endowing metabolic herbicide resistance in plants. This Update presents an historical review to current understanding of metabolic herbicide resistance evolution in weedy plant species. PMID:25106819

Allelopathic principles for sustainable agriculture

USDA-ARS?s Scientific Manuscript database

Allelopathic research of the past few decades has established the feasibility of weed and plant disease management by allelopathic crop plants, plant residues, cultural manipulation, and microorganisms as bioherbicides and rhizobacteria. Inconsistency in the effectiveness of plant-growth-promoting ...

Proving allelopathy in crop-weed interactions

USDA-ARS?s Scientific Manuscript database

Allelopathy (plant/plant chemical warfare) is difficult to prove, especially when competition for resources is the dominant component of plant/plant interference (interference = allelopathy +competition). This paper describes experimental approaches for proving allelopathy and points out common pit...

Conservation systems in the Southeast

USDA-ARS?s Scientific Manuscript database

This presentation describes how conservation systems that include non-inversion tillage and cover crops, a key component of conservation systems, are managed in the Southeast to maximize benefits. Benefits include weed suppression, moisture conservation, and increased organic matter contents. Mana...

Efficacy evaluation of selected herbicides on weed control and productivity evaluation of Bt cotton in Punjab.

PubMed

Singh, Kulvir; Rathore, Pankaj

2015-07-01

Field experiments were conducted during Kharif 2012 and 2013 to evaluate the efficacy of different herbicides for weed management in cotton. Highest seed cotton yield (3537.3 kg ha(-1)) was recorded in weed free plots followed by pendimethalin @1.0 kg a.i ha(-1) as Pre.em.+quizalofopethyl @50 g a.i ha(-1) post-em at 2-4 weed leaf stage + one hoeing (3318.9 kg ha") owing to improved number of bolls per plant and boll weight. Statistically least yield was recorded underweedy check (1435.4 kg ha(-1)). Application of pyrithiobac sodium could not express any visible toxic effect on crop indicating its selectivity for cotton, although none of the tested new chemicals i.e., pyrithiobac sodium@ 62.5g a.i ha(-1) and quizalofopethyl @50g a.i ha(-1) when applied alone could not outperform the existing recommended chemicals for weed management. Yield losses to the extent of 6.2-59.4% were recorded due to weed competition. Weed control efficiency (WCE) was highest under weed free check (86.8%) followed by pendimethalin @1.0 kg a.i ha(-1) as Pre. em.+quizalofopethyl @50g a.i ha(-1), at 2-4 weed leaf stage + one hoeing (73.7%), whereas minimum values were for weedy check (24.7%). Though net returns (r94660 ha(-1)) were highest for weed free check but higher B:C ratio (2:11) was observed for pendimethalin @1.0 kg a.i ha(-1) as Pre em.+quizalofopethyl @50 g a.i ha(-1) post-em at 2-4 weed leaf stage+one hoeing. Therefore, for reasons such as labor shortage besides their timely availability, using these herbicides in combination with cultural practices could be the practical solution foreconomically efficient and effective weed management.

Discriminating crop and other canopies by overlapping binary image layers

NASA Astrophysics Data System (ADS)

Doi, Ryoichi

2013-02-01

For optimal management of agricultural fields by remote sensing, discrimination of the crop canopy from weeds and other objects is essential. In a digital photograph, a rice canopy was discriminated from a variety of weed and tree canopies and other objects by overlapping binary image layers of red-green-blue and other color components indicating the pixels with target canopy-specific (intensity) values based on the ranges of means ±(3×) standard deviations. By overlapping and merging the binary image layers, the target canopy specificity improved to 0.0015 from 0.027 for the yellow 1× standard deviation binary image layer, which was the best among all combinations of color components and means ±(3×) standard deviations. The most target rice canopy-likely pixels were further identified by limiting the pixels at different luminosity values. The discriminatory power was also visually demonstrated in this manner.

Camera sensor arrangement for crop/weed detection accuracy in agronomic images.

PubMed

Romeo, Juan; Guerrero, José Miguel; Montalvo, Martín; Emmi, Luis; Guijarro, María; Gonzalez-de-Santos, Pablo; Pajares, Gonzalo

2013-04-02

In Precision Agriculture, images coming from camera-based sensors are commonly used for weed identification and crop line detection, either to apply specific treatments or for vehicle guidance purposes. Accuracy of identification and detection is an important issue to be addressed in image processing. There are two main types of parameters affecting the accuracy of the images, namely: (a) extrinsic, related to the sensor's positioning in the tractor; (b) intrinsic, related to the sensor specifications, such as CCD resolution, focal length or iris aperture, among others. Moreover, in agricultural applications, the uncontrolled illumination, existing in outdoor environments, is also an important factor affecting the image accuracy. This paper is exclusively focused on two main issues, always with the goal to achieve the highest image accuracy in Precision Agriculture applications, making the following two main contributions: (a) camera sensor arrangement, to adjust extrinsic parameters and (b) design of strategies for controlling the adverse illumination effects.

Increasing Cropping System Diversity Balances Productivity, Profitability and Environmental Health

PubMed Central

Davis, Adam S.; Hill, Jason D.; Chase, Craig A.; Johanns, Ann M.; Liebman, Matt

2012-01-01

Balancing productivity, profitability, and environmental health is a key challenge for agricultural sustainability. Most crop production systems in the United States are characterized by low species and management diversity, high use of fossil energy and agrichemicals, and large negative impacts on the environment. We hypothesized that cropping system diversification would promote ecosystem services that would supplement, and eventually displace, synthetic external inputs used to maintain crop productivity. To test this, we conducted a field study from 2003–2011 in Iowa that included three contrasting systems varying in length of crop sequence and inputs. We compared a conventionally managed 2-yr rotation (maize-soybean) that received fertilizers and herbicides at rates comparable to those used on nearby farms with two more diverse cropping systems: a 3-yr rotation (maize-soybean-small grain + red clover) and a 4-yr rotation (maize-soybean-small grain + alfalfa-alfalfa) managed with lower synthetic N fertilizer and herbicide inputs and periodic applications of cattle manure. Grain yields, mass of harvested products, and profit in the more diverse systems were similar to, or greater than, those in the conventional system, despite reductions of agrichemical inputs. Weeds were suppressed effectively in all systems, but freshwater toxicity of the more diverse systems was two orders of magnitude lower than in the conventional system. Results of our study indicate that more diverse cropping systems can use small amounts of synthetic agrichemical inputs as powerful tools with which to tune, rather than drive, agroecosystem performance, while meeting or exceeding the performance of less diverse systems. PMID:23071739

Increasing cropping system diversity balances productivity, profitability and environmental health.

PubMed

Davis, Adam S; Hill, Jason D; Chase, Craig A; Johanns, Ann M; Liebman, Matt

2012-01-01

Balancing productivity, profitability, and environmental health is a key challenge for agricultural sustainability. Most crop production systems in the United States are characterized by low species and management diversity, high use of fossil energy and agrichemicals, and large negative impacts on the environment. We hypothesized that cropping system diversification would promote ecosystem services that would supplement, and eventually displace, synthetic external inputs used to maintain crop productivity. To test this, we conducted a field study from 2003-2011 in Iowa that included three contrasting systems varying in length of crop sequence and inputs. We compared a conventionally managed 2-yr rotation (maize-soybean) that received fertilizers and herbicides at rates comparable to those used on nearby farms with two more diverse cropping systems: a 3-yr rotation (maize-soybean-small grain + red clover) and a 4-yr rotation (maize-soybean-small grain + alfalfa-alfalfa) managed with lower synthetic N fertilizer and herbicide inputs and periodic applications of cattle manure. Grain yields, mass of harvested products, and profit in the more diverse systems were similar to, or greater than, those in the conventional system, despite reductions of agrichemical inputs. Weeds were suppressed effectively in all systems, but freshwater toxicity of the more diverse systems was two orders of magnitude lower than in the conventional system. Results of our study indicate that more diverse cropping systems can use small amounts of synthetic agrichemical inputs as powerful tools with which to tune, rather than drive, agroecosystem performance, while meeting or exceeding the performance of less diverse systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, Shirley M.; King, Jane R.; Izaurralde, R Cesar C.

Used as cover crops, clover species may differ in their ability to suppress weed growth. Field trials were conducted in Alberta, Canada to measure the growth of brown mustard [Brassica juncea (L.) Czern.], in mowed and nonmowed production, as influenced by alsike (Trifolium hybridum L.), balansa [T. michelianum Savi var. balansae (Boiss.) Azn.], berseem (T. alexandrinum L.), crimson [T. incarnatum (Boiss.) Azn.], berseem (T. alexandrinum L.), crimson (T. incarnatum L.), Persian (T. resupinatum L.), red (T. pratense L.), and white Dutch (T. repens L.) clover and fall rye (Secale cereale L.). In 1997, clovers reduced mustard biomass in nonmowed treatmentsmore » by 29% on a high- fertility soil (Typic Cryoboroll) at Edmonton and by 57% on a low- fertility soil (Typic Cryoboralf) at Breton. At Edmonton, nonmowed mustard biomass was reduced by alsike and berseem clover in 1996 and by alsike, balansa, berseem, and crimson clover in 1997. At Breton, all seven clover species suppressed weed biomass. A negative correlation was noted among clover and mustard biomass at Edmonton but not at Breton. The effects of mowing varied with location, timing, and species. Mowing was beneficial to crop/weed proportion at Edmonton but not at Breton. Mowing at early flowering of mustard large-seeded legumes and sweetclover (Melilotus offici) produced greater benefit than mowing at late flowering. With early mowing, all clover species suppressed mustard growth at Edmonton. Clovers reduced mustard regrowth (g plant21 ) and the number of mustard plants producing regrowth. The characteristics of berseem clover (upright growth, long stems, high biomass, and late flowering) would support its use as a cover crop or forage in north-central Alberta.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patterson, D.T.; Flint, E.P.

Mathematical growth analysis techniques were used to evaluate the effects of CO/sub 2/ concentrations of 350, 600, and 1000 ppm (v/v) on growth and biomass partitioning in corn (Zea mays L. Dekalb (L 395'), itchgrass (Rottboellia exaltata L.f.), soybean (Glycine max L) Merr. Tracy), and velvetleaf (Abutilon theophrasti Medic.). Controlled environment chambers with day/night temperatures of 28/22 C and photosynthetic photon flux densities (PPFD) of 650 ..mu..E (microeinteins) m/sup -2/ s/sup -1/ were used. Dry matter production in the two C/sub 3/ species soybean and velvetleaf) was increased significantly by raising the CO/sub 2/ concentration above 350 ppm. In cornmore » (a C/sub 4/ species), dry matter production was greatest at 600 ppm CO/sub 2/ and did not differ between the 350 and 1000 ppm treatments. Increasing the CO/sub 2/ concentration increased the rate of dry matter production per unit leaf area (net assimilation rate or NAR) in soybean and velvetleaf but either decreased or did not alter NAR in corn and itchgrass. At 45 days after planting, the weed/crop ratios for total dry matter production for velvetleaf/corn and itchgrass/corn were significantly greater at both 600 and 1000 ppm than at 350 ppm CO/sub 2/. The weed/crop ratio for itchgrass/soybean was less at 1000 ppm than at 350 or 600 ppm CO/sub 2/. Compared to the value at 350 ppm, the weed/crop ratio for velvetleaf/soybean was greater at 600 ppm and less at 100 ppm CO/sub 2/.« less

Indicators: Atrazine

EPA Pesticide Factsheets

Atrazine is an herbicide widely used for control of broadleaf and grassy weeds. It is sprayed on row crops such as corn, sorghum and sugarcane, and in some areas is used on residential lawns. It also been used on highway and railroad rights-of-way.

ACETANILIDE HERBICIDE DEGRADATION PRODUCTS BY LC/MS

EPA Science Inventory

Acetanilide herbicides are frequently applied in the U.S. on crops (corn, soybeans, popcorn, etc.) to control broadleaf and annual weeds. The acetanilide and acetamide herbicides currently registered for use in the U.S. are alachlor, acetochlor, metolachlor, propachlor, flufen...

EPA and States' Collective Efforts Lead to Regulatory Action on Dicamba

EPA Pesticide Factsheets

Agreement with Monsanto, BASF and DuPont on measures to further minimize the potential for drift to damage neighboring crops from the use of dicamba formulations used to control weeds in genetically modified cotton and soybeans.

Host plants of the tarnished plant bug (Heteroptera: Miridae) in Central Texas.

PubMed

Esquivel, J F; Mowery, S V

2007-08-01

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has taken on added importance as a pest of cotton in the Cotton Belt after successful eradication efforts for the boll weevil (Anthonomus grandis grandis Boheman). Because the Southern Blacklands region of Central Texas is in advanced stages of boll weevil eradication, blooming weeds and selected row crops were sampled during a 3-yr study to determine lygus species composition and associated temporal host plants. L. lineolaris was the sole lygus species in the region. Thirteen previously unreported host plants were identified for L. lineolaris, of which 69% supported reproduction. Rapistrum rugosum L. Allioni and Ratibida columnifera (Nuttall) Wooton and Standley were primary weed hosts during the early season (17 March to 31 May). Conyza canadensis L. Cronquist variety canadensis and Ambrosia trifida L. were primary weed hosts during the midseason (1 June to 14 August) and late-season (15 August to 30 November), respectively. Sisymbrium irio L. and Lamium amplexicaule L. sustained L. lineolaris populations during the overwintering period (1 December to 16 March). The proportion of females and numbers of nymphs found in R. rugosum, C. canadensis, A. trifida, and S. irio suggests these weeds supported reproductive adults during the early, mid-, and late season and overwintering period, respectively. Medicago sativa L. was the leading crop host for L. lineolaris; Glycine max L. Merrill did not yield L. lineolaris. Few L. lineolaris were collected in Gossypium hirsutum L. These results provide a more comprehensive assessment of host plants contributing to L. lineolaris populations in central Texas.

iMAR: An Interactive Web-Based Application for Mapping Herbicide Resistant Weeds.

PubMed

Panozzo, Silvia; Colauzzi, Michele; Scarabel, Laura; Collavo, Alberto; Rosan, Valentina; Sattin, Maurizio

2015-01-01

Herbicides are the major weed control tool in most cropping systems worldwide. However, the high reliance on herbicides has led to environmental issues as well as to the evolution of herbicide-resistant biotypes. Resistance is a major concern in modern agriculture and early detection of resistant biotypes is therefore crucial for its management and prevention. In this context, a timely update of resistance biotypes distribution is fundamental to devise and implement efficient resistance management strategies. Here we present an innovative web-based application called iMAR (interactive MApping of Resistance) for the mapping of herbicide resistant biotypes. It is based on open source software tools and translates into maps the data reported in the GIRE (Italian herbicide resistance working group) database of herbicide resistance at national level. iMAR allows an automatic, easy and cost-effective updating of the maps a nd provides two different systems, "static" and "dynamic". In the first one, the user choices are guided by a hierarchical tree menu, whereas the latter is more flexible and includes a multiple choice criteria (type of resistance, weed species, region, cropping systems) that permits customized maps to be created. The generated information can be useful to various stakeholders who are involved in weed resistance management: farmers, advisors, national and local decision makers as well as the agrochemical industry. iMAR is freely available, and the system has the potential to handle large datasets and to be used for other purposes with geographical implications, such as the mapping of invasive plants or pests.

Agronomic and environmental implications of enhanced s-triazine degradation

USGS Publications Warehouse

Krutz, L. J.; Dale L. Shaner,; Mark A. Weaver,; Webb, Richard M.; Zablotowicz, Robert M.; Reddy, Krishna N.; Huang, Y.; Thompson, S. J.

2010-01-01

Novel catabolic pathways enabling rapid detoxification of s-triazine herbicides have been elucidated and detected at a growing number of locations. The genes responsible for s-triazine mineralization, i.e. atzABCDEF and trzNDF, occur in at least four bacterial phyla and are implicated in the development of enhanced degradation in agricultural soils from all continents except Antarctica. Enhanced degradation occurs in at least nine crops and six crop rotation systems that rely on s-triazine herbicides for weed control, and, with the exception of acidic soil conditions and s-triazine application frequency, adaptation of the microbial population is independent of soil physiochemical properties and cultural management practices. From an agronomic perspective, residual weed control could be reduced tenfold in s-triazine-adapted relative to non-adapted soils. From an environmental standpoint, the off-site loss of total s-triazine residues could be overestimated 13-fold in adapted soils if altered persistence estimates and metabolic pathways are not reflected in fate and transport models. Empirical models requiring soil pH and s-triazine use history as input parameters predict atrazine persistence more accurately than historical estimates, thereby allowing practitioners to adjust weed control strategies and model input values when warranted. 

Influence of soil properties and soil moisture on the efficacy of indaziflam and flumioxazin on Kochia scoparia L.

PubMed

Sebastian, Derek J; Nissen, Scott J; Westra, Phil; Shaner, Dale L; Butters, Greg

2017-02-01

Kochia (Kochia scoparia L.) is a highly competitive, non-native weed found throughout the western United States. Flumioxazin and indaziflam are two broad-spectrum pre-emergence herbicides that can control kochia in a variety of crop and non-crop situations; however, under dry conditions, these herbicides sometimes fail to control this important weed. There is very little information describing the effect of soil properties and soil moisture on the efficacy of these herbicides. Soil organic matter (SOM) explained the highest proportion of variability in predicting the herbicide dose required for 80% kochia growth reduction (GR 80 ) for flumioxazin and indaziflam (R 2 = 0.72 and 0.79 respectively). SOM had a greater impact on flumioxazin phytotoxicity compared to indaziflam. Flumioxazin and indaziflam kochia phytotoxicity was greatly reduced at soil water potentials below -200 kPa. Kochia can germinate at soil moisture potentials below the moisture required for flumioxazin and indaziflam activation, which means that kochia control is greatly influenced by the complex interaction between soil physical properties and soil moisture. This research can be used to gain a better understanding of how and why some weeds, like kochia, are so difficult to manage even with herbicides that normally provide excellent control. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Crop-to-wild gene flow, introgression and possible fitness effects of transgenes.

PubMed

Jenczewski, Eric; Ronfort, Joëlle; Chèvre, Anne-Marie

2003-01-01

Crop-to-wild gene flow has received close attention over the past ten years in connection with the development and cultivation of transgenic crops. In this paper, we review key examples of crop/wild sympatry and overlapping flowering phenology, pollen and seed dispersal, the barriers to hybridisation and introgression, the evolution and fate of interspecific hybrids, their fitness, and the potential cost of transgenes. We pay particular attention to ways in which the evolution and divergence between crops and their wild relatives may interfere with these successive steps. Our review suggests that crop-to-weed gene flow is highly idiosyncratic and that crop gene dispersion will certainly be very difficult to preclude totally. Future directions for research should thus focus on the long-term establishment and effects of transgenes on natural communities.

Detection of new viruses in alfalfa, weeds and cultivated plants growing adjacent to alfalfa fields in Saudi Arabia.

PubMed

Al-Shahwan, I M; Abdalla, O A; Al-Saleh, M A; Amer, M A

2017-09-01

A total of 1368 symptomatic plant samples showing different virus-like symptoms such as mottling, chlorosis, mosaic, yellow mosaic, vein clearing and stunting were collected from alfalfa, weed and cultivated plant species growing in vicinity of alfalfa fields in five principal regions of alfalfa production in Saudi Arabia. DAS-ELISA test indicated occurrence of 11 different viruses in these samples, 10 of which were detected for the first time in Saudi Arabia. Eighty percent of the alfalfa samples and 97.5% of the weed and cultivated plants samples were found to be infected with one or more of these viruses. Nine weed plant species were found to harbor these viruses namely, Sonchus oleraceus, Chenopodium spp., Hibiscus spp., Cichorium intybus , Convolvulus arvensis , Malva parviflora , Rubus fruticosus , Hippuris vulgaris , and Flaveria trinervia . These viruses were also detected in seven cultivated crop plants growing adjacent to the alfalfa fields including Vigna unguiculata , Solanum tuberosum , Solanum melongena , Phaseolus vulgaris , Cucurbita maxima , Capsicum annuum , and Vicia faba . The newly reported viruses together with their respective percent of detection in alfalfa, and in both weeds and cultivated crop plant species together were as follows: Bean leaf roll virus (BLRV) {12.5 and 4.5%}, Lucerne transient streak virus (LTSV) {2.9 and 3.5%}, Bean yellow mosaic virus (BYMV) {1.4 and 4.5%}, Bean common mosaic virus (BCMV) {1.2 and 4.5%}, Red clover vein mosaic virus (RCVMV) {1.2 and 4%}, White clover mosaic virus (WCIMV) {1.0 and 5%}, Cucumber mosaic virus (CMV) {0.8 and 3%}, Pea streak virus (PeSV) {0.4 and 4.5%} and Tobacco streak virus (TSV) {0.3 and 2.5%}. Alfalfa mosaic virus (AMV), the previously reported virus in alfalfa, had the highest percentage of detection in alfalfa accounting for 58.4% and 62.8% in the weeds and cultivated plants. Peanut stunt virus (PSV) was also detected for the first time in Saudi Arabia with a 66.7% of infection in 90 alfalfa samples collected from the surveyed regions during the last visit that tested negative to all the previously detected viruses.

[Research on identification of cabbages and weeds combining spectral imaging technology and SAM taxonomy].

PubMed

Zu, Qin; Zhang, Shui-fa; Cao, Yang; Zhao, Hui-yi; Dang, Chang-qing

2015-02-01

Weeds automatic identification is the key technique and also the bottleneck for implementation of variable spraying and precision pesticide. Therefore, accurate, rapid and non-destructive automatic identification of weeds has become a very important research direction for precision agriculture. Hyperspectral imaging system was used to capture the hyperspectral images of cabbage seedlings and five kinds of weeds such as pigweed, barnyard grass, goosegrass, crabgrass and setaria with the wavelength ranging from 1000 to 2500 nm. In ENVI, by utilizing the MNF rotation to implement the noise reduction and de-correlation of hyperspectral data and reduce the band dimensions from 256 to 11, and extracting the region of interest to get the spectral library as standard spectra, finally, using the SAM taxonomy to identify cabbages and weeds, the classification effect was good when the spectral angle threshold was set as 0. 1 radians. In HSI Analyzer, after selecting the training pixels to obtain the standard spectrum, the SAM taxonomy was used to distinguish weeds from cabbages. Furthermore, in order to measure the recognition accuracy of weeds quantificationally, the statistical data of the weeds and non-weeds were obtained by comparing the SAM classification image with the best classification effects to the manual classification image. The experimental results demonstrated that, when the parameters were set as 5-point smoothing, 0-order derivative and 7-degree spectral angle, the best classification result was acquired and the recognition rate of weeds, non-weeds and overall samples was 80%, 97.3% and 96.8% respectively. The method that combined the spectral imaging technology and the SAM taxonomy together took full advantage of fusion information of spectrum and image. By applying the spatial classification algorithms to establishing training sets for spectral identification, checking the similarity among spectral vectors in the pixel level, integrating the advantages of spectra and images meanwhile considering their accuracy and rapidity and improving weeds detection range in the full range that could detect weeds between and within crop rows, the above method contributes relevant analysis tools and means to the application field requiring the accurate information of plants in agricultural precision management

Deep RNA-Seq to unlock the gene bank of floral development in Sinapis arvensis.

PubMed

Liu, Jia; Mei, Desheng; Li, Yunchang; Huang, Shunmou; Hu, Qiong

2014-01-01

Sinapis arvensis is a weed with strong biological activity. Despite being a problematic annual weed that contaminates agricultural crop yield, it is a valuable alien germplasm resource. It can be utilized for broadening the genetic background of Brassica crops with desirable agricultural traits like resistance to blackleg (Leptosphaeria maculans), stem rot (Sclerotinia sclerotium) and pod shatter (caused by FRUITFULL gene). However, few genetic studies of S. arvensis were reported because of the lack of genomic resources. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive dataset for S. arvensis for the first time. We used Illumina paired-end sequencing technology to sequence the S. arvensis flower transcriptome and generated 40,981,443 reads that were assembled into 131,278 transcripts. We de novo assembled 96,562 high quality unigenes with an average length of 832 bp. A total of 33,662 full-length ORF complete sequences were identified, and 41,415 unigenes were mapped onto 128 pathways using the KEGG Pathway database. The annotated unigenes were compared against Brassica rapa, B. oleracea, B. napus and Arabidopsis thaliana. Among these unigenes, 76,324 were identified as putative homologs of annotated sequences in the public protein databases, of which 1194 were associated with plant hormone signal transduction and 113 were related to gibberellin homeostasis/signaling. Unigenes that did not match any of those sequence datasets were considered to be unique to S. arvensis. Furthermore, 21,321 simple sequence repeats were found. Our study will enhance the currently available resources for Brassicaceae and will provide a platform for future genomic studies for genetic improvement of Brassica crops.

Deep RNA-Seq to Unlock the Gene Bank of Floral Development in Sinapis arvensis

PubMed Central

Liu, Jia; Mei, Desheng; Li, Yunchang; Huang, Shunmou; Hu, Qiong

2014-01-01

Sinapis arvensis is a weed with strong biological activity. Despite being a problematic annual weed that contaminates agricultural crop yield, it is a valuable alien germplasm resource. It can be utilized for broadening the genetic background of Brassica crops with desirable agricultural traits like resistance to blackleg (Leptosphaeria maculans), stem rot (Sclerotinia sclerotium) and pod shatter (caused by FRUITFULL gene). However, few genetic studies of S. arvensis were reported because of the lack of genomic resources. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive dataset for S. arvensis for the first time. We used Illumina paired-end sequencing technology to sequence the S. arvensis flower transcriptome and generated 40,981,443 reads that were assembled into 131,278 transcripts. We de novo assembled 96,562 high quality unigenes with an average length of 832 bp. A total of 33,662 full-length ORF complete sequences were identified, and 41,415 unigenes were mapped onto 128 pathways using the KEGG Pathway database. The annotated unigenes were compared against Brassica rapa, B. oleracea, B. napus and Arabidopsis thaliana. Among these unigenes, 76,324 were identified as putative homologs of annotated sequences in the public protein databases, of which 1194 were associated with plant hormone signal transduction and 113 were related to gibberellin homeostasis/signaling. Unigenes that did not match any of those sequence datasets were considered to be unique to S. arvensis. Furthermore, 21,321 simple sequence repeats were found. Our study will enhance the currently available resources for Brassicaceae and will provide a platform for future genomic studies for genetic improvement of Brassica crops. PMID:25192023

Escape to Ferality: The Endoferal Origin of Weedy Rice from Crop Rice through De-Domestication

PubMed Central

Gettler, Kyle A.; Burgos, Nilda R.; Fischer, Albert J.

2016-01-01

Domestication is the hallmark of evolution and civilization and harnesses biodiversity through selection for specific traits. In regions where domesticated lines are grown near wild relatives, congeneric sources of aggressive weedy genotypes cause major economic losses. Thus, the origins of weedy genotypes where no congeneric species occur raise questions regarding management effectiveness and evolutionary mechanisms responsible for weedy population success. Since eradication in the 1970s, California growers avoided weedy rice through continuous flood culture and zero-tolerance guidelines, preventing the import, presence, and movement of weedy seeds. In 2003, after decades of no reported presence in California, a weedy rice population was confirmed in dry-seeded fields. Our objectives were to identify the origins and establishment of this population and pinpoint possible phenotypes involved. We show that California weedy rice is derived from a different genetic source among a broad range of AA genome Oryzas and is most recently diverged from O. sativa temperate japonica cultivated in California. In contrast, other weedy rice ecotypes in North America (Southern US) originate from weedy genotypes from China near wild Oryza, and are derived through existing crop-wild relative crosses. Analyses of morphological data show that California weedy rice subgroups have phenotypes like medium-grain or gourmet cultivars, but have colored pericarp, seed shattering, and awns like wild relatives, suggesting that reversion to non-domestic or wild-like traits can occur following domestication, despite apparent fixation of domestication alleles. Additionally, these results indicate that preventive methods focused on incoming weed sources through contamination may miss burgeoning weedy genotypes that rapidly adapt, establish, and proliferate. Investigating the common and unique evolutionary mechanisms underlying global weed origins and subsequent interactions with crop relatives sheds light on how weeds evolve and addresses broader questions regarding the stability of selection during domestication and crop improvement. PMID:27661982

Escape to Ferality: The Endoferal Origin of Weedy Rice from Crop Rice through De-Domestication.

PubMed

Kanapeckas, Kimberly L; Vigueira, Cynthia C; Ortiz, Aida; Gettler, Kyle A; Burgos, Nilda R; Fischer, Albert J; Lawton-Rauh, Amy L

Domestication is the hallmark of evolution and civilization and harnesses biodiversity through selection for specific traits. In regions where domesticated lines are grown near wild relatives, congeneric sources of aggressive weedy genotypes cause major economic losses. Thus, the origins of weedy genotypes where no congeneric species occur raise questions regarding management effectiveness and evolutionary mechanisms responsible for weedy population success. Since eradication in the 1970s, California growers avoided weedy rice through continuous flood culture and zero-tolerance guidelines, preventing the import, presence, and movement of weedy seeds. In 2003, after decades of no reported presence in California, a weedy rice population was confirmed in dry-seeded fields. Our objectives were to identify the origins and establishment of this population and pinpoint possible phenotypes involved. We show that California weedy rice is derived from a different genetic source among a broad range of AA genome Oryzas and is most recently diverged from O. sativa temperate japonica cultivated in California. In contrast, other weedy rice ecotypes in North America (Southern US) originate from weedy genotypes from China near wild Oryza, and are derived through existing crop-wild relative crosses. Analyses of morphological data show that California weedy rice subgroups have phenotypes like medium-grain or gourmet cultivars, but have colored pericarp, seed shattering, and awns like wild relatives, suggesting that reversion to non-domestic or wild-like traits can occur following domestication, despite apparent fixation of domestication alleles. Additionally, these results indicate that preventive methods focused on incoming weed sources through contamination may miss burgeoning weedy genotypes that rapidly adapt, establish, and proliferate. Investigating the common and unique evolutionary mechanisms underlying global weed origins and subsequent interactions with crop relatives sheds light on how weeds evolve and addresses broader questions regarding the stability of selection during domestication and crop improvement.

Effects of climate change on croplands

EPA Science Inventory

This talk will describe likely changes in temperature and precipitation expected in the northwestern US with global climate change, and their potential impacts on Oregon croplands. The focus will be on the effects of temperature and carbon dioxide on crop productivity, weed cont...

Benefits of increasing plant diversity in sustainable agroecosystems

USDA-ARS?s Scientific Manuscript database

Recent studies have revealed many potential benefits of increasing plant diversity in agroecosystems and production forests, including enhancing yields of crops, forage, and wood; stabilizing yields across time and space; enhancing pollinators and pollination; suppressing weeds and other pests; and ...

Managing the evolution of herbicide resistance

USDA-ARS?s Scientific Manuscript database

Herbicide-resistant (HR) weeds are widespread threats to the sustainability, productivity, and profitability of many cropping systems. Efforts to combat their spread through herbicide rotation schedules have been marginally effective at best. Despite the scope of the problem, we lack sound empirical...

Climate change increases the risk of herbicide-resistant weeds due to enhanced detoxification.

PubMed

Matzrafi, Maor; Seiwert, Bettina; Reemtsma, Thorsten; Rubin, Baruch; Peleg, Zvi

2016-12-01

Global warming will increase the incidence of metabolism-based reduced herbicide efficacy on weeds and, therefore, the risk for evolution of non-target site herbicide resistance. Climate changes affect food security both directly and indirectly. Weeds are the major biotic factor limiting crop production worldwide, and herbicides are the most cost-effective way for weed management. Processes associated with climatic changes, such as elevated temperatures, can strongly affect weed control efficiency. Responses of several grass weed populations to herbicides that inhibit acetyl-CoA carboxylase (ACCase) were examined under different temperature regimes. We characterized the mechanism of temperature-dependent sensitivity and the kinetics of pinoxaden detoxification. The products of pinoxaden detoxification were quantified. Decreased sensitivity to ACCase inhibitors was observed under elevated temperatures. Pre-treatment with the cytochrome-P450 inhibitor malathion supports a non-target site metabolism-based mechanism of herbicide resistance. The first 48 h after herbicide application were crucial for pinoxaden detoxification. The levels of the inactive glucose-conjugated pinoxaden product (M5) were found significantly higher under high- than low-temperature regime. Under high temperature, a rapid elevation in the level of the intermediate metabolite (M4) was found only in pinoxaden-resistant plants. Our results highlight the quantitative nature of non-target-site resistance. To the best of our knowledge, this is the first experimental evidence for temperature-dependent herbicide sensitivity based on metabolic detoxification. These findings suggest an increased risk for the evolution of herbicide-resistant weeds under predicted climatic conditions.

Foundational and Translational Research Opportunities to Improve Plant Health

PubMed Central

Michelmore, Richard; Coaker, Gitta; Bart, Rebecca; Beattie, Gwyn; Bent, Andrew; Bruce, Toby; Cameron, Duncan; Dangl, Jeff; Dinesh-Kumar, Savithramma; Edwards, Rob; Eves-van den Akker, Sebastian; Gassmann, Walter; Greenberg, Jean; Harrison, Richard; He, Ping; Hanley-Bowdoin, Linda; Harvey, Jagger; Huffaker, Alisa; Hulbert, Scot; Innes, Roger; Jones, Jonathan; Kaloshian, Isgouhi; Kamoun, Sophien; Katagiri, Fumiaki; Leach, Jan; Ma, Wenbo; McDowell, John; Medford, June; Meyers, Blake; Nelson, Rebecca; Oliver, Richard; Qi, Yiping; Saunders, Diane; Shaw, Michael; Smart, Christine; Subudhi, Prasanta; Torrance, Lesley; Tyler, Bret; Valent, Barbara; Walsh, John

2018-01-01

Summary This whitepaper reports the deliberations of a workshop focused on biotic challenges to plant health held in Washington, D.C. in September 2016. Ensuring health of food plants is critical to maintaining the quality and productivity of crops and for sustenance of the rapidly growing human population. There is a close linkage between food security and societal stability; however, global food security is threatened by the vulnerability of our agricultural systems to numerous pests, pathogens, weeds, and environmental stresses. These threats are aggravated by climate change, the globalization of agriculture, and an over-reliance on non-sustainable inputs. New analytical and computational technologies are providing unprecedented resolution at a variety of molecular, cellular, organismal, and population scales for crop plants as well as pathogens, pests, beneficial microbes, and weeds. It is now possible to both characterize useful or deleterious variation as well as precisely manipulate it. Data-driven, informed decisions based on knowledge of the variation of biotic challenges and of natural and synthetic variation in crop plants will enable deployment of durable interventions throughout the world. These should be integral, dynamic components of agricultural strategies for sustainable agriculture. PMID:28398839

Measuring Rates of Herbicide Metabolism in Dicot Weeds with an Excised Leaf Assay

PubMed Central

Ma, Rong; Skelton, Joshua J.; Riechers, Dean E.

2015-01-01

In order to isolate and accurately determine rates of herbicide metabolism in an obligate-outcrossing dicot weed, waterhemp (Amaranthus tuberculatus), we developed an excised leaf assay combined with a vegetative cloning strategy to normalize herbicide uptake and remove translocation as contributing factors in herbicide-resistant (R) and –sensitive (S) waterhemp populations. Biokinetic analyses of organic pesticides in plants typically include the determination of uptake, translocation (delivery to the target site), metabolic fate, and interactions with the target site. Herbicide metabolism is an important parameter to measure in herbicide-resistant weeds and herbicide-tolerant crops, and is typically accomplished with whole-plant tests using radiolabeled herbicides. However, one difficulty with interpreting biokinetic parameters derived from whole-plant methods is that translocation is often affected by rates of herbicide metabolism, since polar metabolites are usually not mobile within the plant following herbicide detoxification reactions. Advantages of the protocol described in this manuscript include reproducible, accurate, and rapid determination of herbicide degradation rates in R and S populations, a substantial decrease in the amount of radiolabeled herbicide consumed, a large reduction in radiolabeled plant materials requiring further handling and disposal, and the ability to perform radiolabeled herbicide experiments in the lab or growth chamber instead of a greenhouse. As herbicide resistance continues to develop and spread in dicot weed populations worldwide, the excised leaf assay method developed and described herein will provide an invaluable technique for investigating non-target site-based resistance due to enhanced rates of herbicide metabolism and detoxification. PMID:26383604

Herbicides and plant hormesis.

PubMed

Belz, Regina G; Duke, Stephen O

2014-05-01

Herbicide hormesis is commonly observed at subtoxic doses of herbicides and other phytotoxins. The occurrence and magnitude of this phenomenon are influenced by plant growth stage and physiological status, environmental factors, the endpoint measured and the timing between treatment and endpoint measurement. The mechanism in some cases of herbicide hormesis appears to be related to the target site of the herbicide, whereas in other examples hormesis may be by overcompensation to moderate stress induced by the herbicides or a response to disturbed homeostasis. Theoretically, herbicide hormesis could be used in crop production, but this has been practical only in the case of the use of herbicides as sugar cane 'ripeners' to enhance sucrose accumulation. The many factors that can influence the occurrence, the magnitude and the dose range of hormetic increases in yield for most crops make it too unpredictable and risky as a production practice with the currently available knowledge. Herbicide hormesis can cause undesired effects in situations in which weeds are unintentionally exposed to hormetic doses (e.g. in adjacent fields, when shielded by crop vegetation). Some weeds that have evolved herbicide resistance may have hormetic responses to recommended herbicide application rates. Little is known about such effects under field conditions. A more complete understanding of herbicide hormesis is needed to exploit its potential benefits and to minimize its potential harmful effects in crop production. © 2014 Society of Chemical Industry.

Metabolism-based herbicide resistance and cross-resistance in crop weeds: a threat to herbicide sustainability and global crop production.

PubMed

Yu, Qin; Powles, Stephen

2014-11-01

Weedy plant species that have evolved resistance to herbicides due to enhanced metabolic capacity to detoxify herbicides (metabolic resistance) are a major issue. Metabolic herbicide resistance in weedy plant species first became evident in the 1980s in Australia (in Lolium rigidum) and the United Kingdom (in Alopecurus myosuroides) and is now increasingly recognized in several crop-weed species as a looming threat to herbicide sustainability and thus world crop production. Metabolic resistance often confers resistance to herbicides of different chemical groups and sites of action and can extend to new herbicide(s). Cytochrome P450 monooxygenase, glycosyl transferase, and glutathione S-transferase are often implicated in herbicide metabolic resistance. However, precise biochemical and molecular genetic elucidation of metabolic resistance had been stalled until recently. Complex cytochrome P450 superfamilies, high genetic diversity in metabolic resistant weedy plant species (especially cross-pollinated species), and the complexity of genetic control of metabolic resistance have all been barriers to advances in understanding metabolic herbicide resistance. However, next-generation sequencing technologies and transcriptome-wide gene expression profiling are now revealing the genes endowing metabolic herbicide resistance in plants. This Update presents an historical review to current understanding of metabolic herbicide resistance evolution in weedy plant species. © 2014 American Society of Plant Biologists. All Rights Reserved.

Rhizome Fragmentation by Vertical Disks Reduces Elymus repens Growth and Benefits Italian Ryegrass-White Clover Crops

PubMed Central

Ringselle, Björn; Bertholtz, Erik; Magnuski, Ewa; Brandsæter, Lars Olav; Mangerud, Kjell; Bergkvist, Göran

2018-01-01

Tillage controls perennial weeds, such as Elymus repens, partly because it fragments their underground storage organs. However, tillage is difficult to combine with a growing crop, which limits its application. The aim of this study was to evaluate how soil vertical cutting with minimum soil disturbance and mowing affect the growth and competitive ability of E. repens in a grass–clover crop. A tractor-drawn prototype with vertical disks was used to fragment E. repens rhizomes with minimal soil and crop disturbance. In experiments performed in 2014 and 2015 at a field site close to Uppsala, Sweden, the rhizomes were fragmented before crop sowing (ERF), during crop growth (LRF), or both (ERF+LRF). Fragmentation was combined with repeated mowing (yes/no) and four companion crop treatments (none, Italian ryegrass, white clover, and grass/clover mixture). The results showed that in the grass–clover crop, rhizome fragmentation reduced E. repens rhizome biomass production and increased Italian ryegrass shoot biomass. ERF and LRF both reduced E. repens rhizome biomass by about 38% compared with the control, while ERF+LRF reduced it by 63%. Italian ryegrass shoot biomass was increased by 78% by ERF, 170% by LRF and 200% by ERF+LRF. Repeated mowing throughout the experiment reduced E. repens rhizome biomass by about 75%. Combining repeated mowing with rhizome fragmentation did not significantly increase the control effect compared to mowing alone. We concluded that rhizome fragmentation using vertical disks can be used both before sowing and during crop growth to enhance the controlling effect of grass–clover crops on E. repens. PMID:29375611

Weed Control for Establishing Intensively Cultured Hybrid Poplar Plantations

Treesearch

Edward Hansen; Daniel Netzer; W.J. Rietveld

1984-01-01

Compares effeects of various wee-control methods, including hericides, cultivation, and legume cover crop, on tree survival and height growth of 2-year-old hybrid poplars. Cultivation and herbicides singly or in combination gave consistently better results than the other treatment tested.

Ammonium nonanoate broadcast application over onions

USDA-ARS?s Scientific Manuscript database

Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Racer (40% ammonium nonaoate) is a potential contact herbicide for weed control in organic crop production. Field research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determin...

USDA,ARS areawide project-Anaoerobic soil disinfestation

USDA-ARS?s Scientific Manuscript database

Anaerobic soil disinfestation (ASD) is an effective method for control of soilborne pathogens, nematodes, and many weed species. In the absence of pest pressure, ASD provides increased yields of multiple crop species. Utilization of ASD requires the application of organic amendments, such as compos...

Effects of mixtures of dicamba and glyphosate on nontarget plants

EPA Science Inventory

New technologies are being developed using mixtures of herbicides to manage a broader variety of weeds in multiple herbicide resistant crops such as soybean and cotton. As part of its regulation of pesticides, the US Environmental Protection Agency considers environmental risks,...

METHOD DEVELOPMENT FOR ALACHLOR ESA AND OTHER ACENTANILIDE HERBICIDE DEGRADATION PRODUCTS

EPA Science Inventory

Introduction: Acetanilide herbicides are frequently applied in the U.S. on crops (corn, soybeans, popcorn, etc.) to control broadleaf and annual weeds. The acetanilide and acetamide herbicides currently registered for use in the U.S. are alachlor, acetochlor, metolachlor, propa...

Thiamethoxam as a seed treatment alters the physiological response of maize (Zea mays) seedlings to neighbouring weeds.

PubMed

Afifi, Maha; Lee, Elizabeth; Lukens, Lewis; Swanton, Clarence

2015-04-01

Thiamethoxam is a broad-spectrum neonicotinoid insecticide that, when applied to seed, has been observed to enhance seedling vigour under environmental stress conditions. Stress created by the presence of neighbouring weeds is known to trigger the accumulation of hydrogen peroxide (H2 O2 ) in maize seedling tissue. No previous work has explored the effect of thiamethoxam as a seed treatment on the physiological response of maize seedlings emerging in the presence of neighbouring weeds. Thiamethoxam was found to enhance seedling vigour and to overcome the expression of typical shade avoidance characteristics in the presence of neighbouring weeds. These results were attributed to maintenance of the total phenolics content, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity and anthocyanin and lignin contents. These findings were also associated with the activation of scavenging genes, which reduced the accumulation of H2 O2 and the subsequent damage caused by lipid peroxidation in maize seedlings originating from treated seeds even when exposed to neighbouring weeds. These results suggest the possibility of exploring new chemistries and modes of action as novel seed treatments to upregulate free radical scavenging genes and to maintain the antioxidant system within plants. Such an approach may provide an opportunity to enhance crop competitiveness with weeds. © 2014 Society of Chemical Industry.

Effect of pre-planting irrigation, maize planting pattern and nitrogen on weed seed bank population.

PubMed

Hemmati, E; Vazan, S; Oveisi, M

2011-01-01

Pre-planting irrigation and planting patterns are important factors in weed management that effect on seed bank. Additionally, the nitrogen is the most important factor in plant growth that affects weed-crop competition and ultimately, seed rain into the soil. A field experiment was conducted to study the effect of nitrogen application rates, pre-planting irrigation and maize planting patterns on weed seed bank population. Experimental factors were nitrogen rates at 4 levels (200, 300, 400 and 500 kg per hectare) as main plot; and pre-planting irrigation at 2 levels (irrigation before planting plus weeding emerged seedlings and, irrigation after sowing), and maize planting patterns (one-row and two-row planting of maize with same density per square of row length) that were assigned in a factorial arrangement to the sub plots. Soil samples were taken at the beginning of the season (before planting of maize) and at the end of the season (after harvest) at depth of 0-5 cm in the fixed quadrates (60 cm x 60 cm). The weed seeds were extracted from the soil samples and were identified using standard methods. The majority of weed seed bank populations included 6 weed species: Portulaca oleracea, Chenopodium album, Amaranthus retroflexus, Sorghum halepense, Daturea stramonium, Xanthium strumarium. Results showed that population of weed seed bank increased significantly with increasing nitrogen rate. The increasing rate was different between one-row and two-row planting patterns. The parameters indicated that seed bank population was much higher in a one row planting pattern of maize. With two-row planting, seed bank was decreased by 34, 26, 20 and 5% at 200, 300, 400 and 500 kg N/ha, respectively. Pre-planting irrigation was also found an effective implement to reduce the weed seed bank. When pre-planting irrigation was applied, seed bank was decreased by 57, 43, 34 and 9% at 200, 300, 400 and 500 kg N/ha. Increasing nitrogen because of weed's better growth and higher seed production neutralized the decreasing effect of pre-planting irrigation and two-row planting of maize on weed seed bank population.

Safety assessment of foods from genetically modified crops in countries with developing economies.

PubMed

Delaney, Bryan

2015-12-01

Population growth particularly in countries with developing economies will result in a need to increase food production by 70% by the year 2050. Biotechnology has been utilized to produce genetically modified (GM) crops for insect and weed control with benefits including increased crop yield and will also be used in emerging countries. A multicomponent safety assessment paradigm has been applied to individual GM crops to determine whether they as safe as foods from non-GM crops. This paper reviews methods to assess the safety of foods from GM crops for safe consumption from the first generation of GM crops. The methods can readily be applied to new products developed within country and this paper will emphasize the concept of data portability; that safety data produced in one geographic location is suitable for safety assessment regardless of where it is utilized. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Synthesis and evaluation of heterocyclic analogues of bromoxynil.

PubMed

Cutulle, Matthew A; Armel, Gregory R; Brosnan, James T; Best, Michael D; Kopsell, Dean A; Bruce, Barry D; Bostic, Heidi E; Layton, Donovan S

2014-01-15

One attractive strategy to discover more active and/or crop-selective herbicides is to make structural changes to currently registered compounds. This strategy is especially appealing for those compounds with limited herbicide resistance and whose chemistry is accompanied with transgenic tools to enable herbicide tolerance in crop plants. Bromoxynil is a photosystem II (PSII) inhibitor registered for control of broadleaf weeds in several agronomic and specialty crops. Recently at the University of Tennessee-Knoxville several analogues of bromoxynil were synthesized including a previously synthesized pyridine (2,6-dibromo-5-hydroxypyridine-2-carbonitrile sodium salt), a novel pyrimidine (4,6-dibromo-5-hydroxypyrimidine-2-carbonitrile sodium salt), and a novel pyridine N-oxide (2,6-dibromo-1-oxidopyridin-1-ium-4-carbonitrile). These new analogues of bromoxynil were also evaluated for their herbicidal activity on soybean (Glycine max), cotton (Gossypium hirsutum), redroot pigweed (Amaranthus retroflexus), velvetleaf (Abutilon theophrasti), large crabgrass (Digitaria sanguinalis), and pitted morningglory ( Ipomoea lacunose ) when applied at 0.28 kg ha(-1). A second study was conducted on a glyphosate-resistant weed (Amaranthus palmeri) with the compounds being applied at 0.56 kg ha(-1). Although all compounds were believed to inhibit PSII by binding in the quinone binding pocket of D1, the pyridine and pyridine-N-oxide analogues were clearly more potent than bromoxynil on Amaranthus retroflexus. However, application of the pyrimidine herbicide resulted in the least injury to all species tested. These variations in efficacy were investigated using molecular docking simulations, which indicate that the pyridine analogue may form a stronger hydrogen bond in the pocket of the D1 protein than the original bromoxynil. A pyridine analogue was able to control the glyphosate-resistant Amaranthus palmeri with >80% efficacy. The pyridine analogues of bromoxynil showed potential to have a different weed control spectrum compared to bromoxynil. A pyridine analogue of bromoxynil synthesized in this research controlled several weed species greater than bromoxynil itself, potentially due to enhanced binding within the PSII binding pocket. Future research should compare this analogue to bromoxynil using optimized formulations at higher application rates.

Tempest in a tea pot: How did the public conversation on genetically modified crops drift so far from the facts?

PubMed

Goldstein, Daniel A

2014-06-01

The debate over genetically modified (GM) crops has raged in Europe since 1996, but had barely risen above a whisper in the USA until recent labeling debates raised public attention. This article will explain GM crops and traits discuss safety assessment provide a view on safety from authoritative organizations discuss selected issues of current debate, and provide the author's perspective as to why the public debate has drifted so far from scientific reality. The economic and environmental benefits of GM crops are beyond scope, but references are provided. GM food and feed undergo comprehensive assessments using recognized approaches to assure they are as safe as the conventional congener. Issues of food safety and nutrition, unrelated to the GM process, may arise when GM foods display novel components or composition. Unanticipated genetic effects in GM crops appear to be limited in contrast to existing variations among conventional varieties resulting from breeding, mutation, and natural mobile genetic elements. Allergenic potential is assessed when selecting genes for introduction into GM crops and remains a theoretical risk to date. Emerging weed and insect resistance is not unique to GM technology and will require the use of integrated pest management/best practices for pest control. Gene flow from GM crops to wild relatives is limited by existing biological barriers but can at time be a relevant consideration in gene selection and planting practices. Insect-resistant GM crops have significantly reduced use of chemical insecticides and appear to have reduced the incidence of pesticide poisoning in areas where small scale farming and hand application are common. Changes in herbicide patterns are more complex and are evolving over time in response to weed resistance management needs. Recent public debate is driven by a combination of unfounded allegations about the technology and purveyors, pseudoscience, and attempts to apply a strict precautionary principle.

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass.

PubMed

Gaba, Sabrina; Collas, Claire; Powolny, Thibaut; Bretagnolle, François; Bretagnolle, Vincent

2014-10-01

The trade-off between forage quality and quantity has been particularly studied in herbivore organisms, but much less for seed eating animals, in particular seed-eating birds which constitute the bulk of wintering passerines in European farmlands. The skylark is one of the commonest farmland birds in winter, mainly feeding on seeds. We focus on weed seeds for conservation and management purposes. Weed seeds form the bulk of the diet of skylarks during winter period, and although this is still a matter for discussion, weed seed predation by granivorous has been suggested as an alternative to herbicides used to regulate weed populations in arable crops. Our objectives were to identify whether weed seed traits govern foraging decisions of skylarks, and to characterize key seed traits with respect to size, which is related to searching and handling time, and lipid content, which is essential for migratory birds. We combined a single-offer experiment and a multiple-offer one to test for feeding preferences of the birds by estimating seed intake on weed seed species differing in their seed size and seed lipid content. Our results showed (1) a selective preference for smaller seeds above a threshold of seed size or seed size difference in the pair and, (2) a significant effect of seed lipid biomass suggesting a trade-off between foraging for smaller seeds and selecting seeds rich in lipids. Skylarks foraging decision thus seems to be mainly based on seed size, that is presumably a 'proxy' for weed seed energy content. However, there are clearly many possible combinations of morphological and physiological traits that must play crucial role in the plant-bird interaction such as toxic compound or seed coat. Copyright © 2014 Elsevier B.V. All rights reserved.

Evaluation of UAV imagery for mapping Silybum marianum weed patches

USDA-ARS?s Scientific Manuscript database

The invasive weed, milk thistle (Silybum marianum), has the tendency to grow in patches. In order to perform site-specific weed management, determining the spatial distribution of weeds is important for its eradication. Remote sensing has been used to perform species discrimination, and it offers pr...

Plant Mulches Can Help Weed Management in Ukraine

USDA-ARS?s Scientific Manuscript database

Producers in the United States are interested in restoring the health of their soils to improve crop production. Decades of tillage have severely damaged soil structure and functioning. Eliminating tillage from production systems has repaired some of this damage to soil. Producers and scientists ...

2008 Volunteer Potato Outlook

USDA-ARS?s Scientific Manuscript database

Potato tubers left in the ground following a potato harvest often over winter in regions with mild winter temperatures resulting in a serious and difficult to manage weed problem in the ensuing crop rotation. Potatoes normally are killed when they reach temperatures below 28° F. Winter soil tempera...

ANALYTICAL METHOD DEVELOPMENT FOR ALACHLOR ESA AND OTHER ACETANILIDE PESTICIDE TRANSFORMATION PRODUCTS

EPA Science Inventory

Acetanilide herbicides are frequently applied in the U.S. on crops (corn, soybeans, popcorn, etc.) to control broadleaf and annual weeds. The acetanilide herbicides currently registered for use in the U.S. are: alachlor, acetochlor, metolachlor, propachlor, dimethenamid and fluf...

The evolution of flowering strategies in US weedy rice

USDA-ARS?s Scientific Manuscript database

Local adaptation in plants often involves changes in flowering time in response to day length and temperature differences. Many crop varieties have been selected for uniformity in flowering time. In contrast, variable flowering may be important for increased competitiveness in weed species invading ...

LAKE MICHIGAN MASS BALANCE PROJECT: ATRAZINE MODELLING RESULTS

EPA Science Inventory

The triazine herbicide, atrazine, is used worldwide to control broadleaf and grassy weeds in agricultural regions. Atrazine is extensively used for corn crops in the midwestern US, the Great Lakes region, and in the Lake Michigan basin and has been cited as an emerging pollutant ...

The archaeobotany of Asian rice expansion and the development of wet-field cultivation

NASA Astrophysics Data System (ADS)

Fuller, D.

2008-12-01

Archaeobotanical evidence provides direct data on past human diet and agriculture, including a geographical and chronological framework for studying the expansion of rice agriculture. The growth of systematic archaeobotanical sampling in recent years has allowed for the past presence of rice to be seen in relation to cultivation of other crops and associated weeds. The weed flora provides a basis for inferring the nature of cultivation systems, whether rain-fed dry rice or wetland "paddy" rice, a key distinction for considerations of past methane production. Nevertheless, current data is very unevenly distributed. This poster will summarize available evidence for the origins and spread of rice in South Asia (India and Pakistan), and mainland and Island Southeast Asia deriving from an earlier Chinese domestication. Where possible, such as in India or China, the potential of the weed flora remains for distinguishing wetland rice crops will be summarized. In broad terms, although the origins of rice use and cultivation begins by or during the Middle Holocene (6000- 3000 BC), rice cultivation spread outside the regions of the wild progenitor after this time. Two phases of rice expansion can be distinguished. Phase 1, between 3000 and 1500 BC, introduced rice to Southeast Asia, probably under wetland cultivation, and the spread of dry rice over northern India and Pakistan. Phase 2, taking place between 1000 and 0 BC, sees the spread of rice throughout the Southern Indian Peninsula, with weed evidence suggesting irrigated wetland rice. Similarly, this period sees the spread of intensive paddy agriculture through Korea and Japan, but in Southeast Asia is probably related to a spread of rice in upland, dry field systems.

Effect of management and soil moisture regimes on wetland soils total carbon and nitrogen in Tanzania

NASA Astrophysics Data System (ADS)

Kamiri, Hellen; Kreye, Christine; Becker, Mathias

2013-04-01

Wetland soils play an important role as storage compartments for water, carbon and nutrients. These soils implies various conditions, depending on the water regimes that affect several important microbial and physical-chemical processes which in turn influence the transformation of organic and inorganic components of nitrogen, carbon, soil acidity and other nutrients. Particularly, soil carbon and nitrogen play an important role in determining the productivity of a soil whereas management practices could determine the rate and magnitude of nutrient turnover. A study was carried out in a floodplain wetland planted with rice in North-west Tanzania- East Africa to determine the effects of different management practices and soil water regimes on paddy soil organic carbon and nitrogen. Four management treatments were compared: (i) control (non weeded plots); (ii) weeded plots; (iii) N fertilized plots, and (iv) non-cropped (non weeded plots). Two soil moisture regimes included soil under field capacity (rainfed conditions) and continuous water logging compared side-by-side. Soil were sampled at the start and end of the rice cropping seasons from the two fields differentiated by moisture regimes during the wet season 2012. The soils differed in the total organic carbon and nitrogen between the treatments. Soil management including weeding and fertilization is seen to affect soil carbon and nitrogen regardless of the soil moisture conditions. Particularly, the padddy soils were higher in the total organic carbon under continuous water logged field. These findings are preliminary and a more complete understanding of the relationships between management and soil moisture on the temporal changes of soil properties is required before making informed decisions on future wetland soil carbon and nitrogen dynamics. Keywords: Management, nitrogen, paddy soil, total carbon, Tanzania,