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1

Weed Airport, Weed, California.  

National Technical Information Service (NTIS)

The report describes the proposal for the runway realignment and 300' extension of Weed Airport. The adverse environmental impact of this project will include the construction process and minor secondary impact. (Author)

1972-01-01

2

Agronomic Weeds.  

ERIC Educational Resources Information Center

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…

Hartwig, Nathan L.

3

Flowers & Weeds.  

ERIC Educational Resources Information Center

Describes the topics and teaching strategies employed in an Issues in Biology course. Discusses flowers, plant breeding, potatoes and tomatoes, the chocolate tree, weeds, Arabidopis, gene transfers, and plant genes/human genes. Contains 22 references. (JRH)

Flannery, Maura C.

1996-01-01

4

Green Weeding  

ERIC Educational Resources Information Center

Gone are the days of tiptoeing to the dumpsters with boxes of weeded books in tow. Lots of libraries are now taking advantage of the many low-cost services and solutions that promise to help extend the lives of collection discards. Some of these options can be very profitable. Some create goodwill within the local community. Some may seem more…

Penniman, Sarah; McColl, Lisa

2008-01-01

5

Eradication of Major Weeds  

ERIC Educational Resources Information Center

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)

Indian Journal of Adult Education, 1975

1975-01-01

6

Introduction to Weeds and Herbicides.  

ERIC Educational Resources Information Center

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…

Hartwig, Nathan L.

7

Weed Control in Rice.  

National Technical Information Service (NTIS)

A conference on weed control in rice held at Los Banos, the Philippines, underscored the importance of the advance of weed science as a major factor in improving rice production. Proceedings of the conference, herein presented, consist of 33 studies in su...

1981-01-01

8

Weeds on the Web  

NSDL National Science Digital Library

The Wildland Invasive Species Program of The Nature Conservancy (TNC) hosts this interesting and light-hearted page on the invasive plants currently threatening the biodiversity of wild lands in the US. Appropriate for undergraduates, educators will find much here on weeds (what they are, which ones are worst), weed control methods, and suggestions for including action in lesson plans. For starters, click on any state in the US map to find out about the worst invasive plants in that state. Those seeking detailed information should consult the Element Stewardship Abstracts, which describe over 100 species in terms of Scientific and Common Name, Description of Characteristics, Biology/ Ecology, Global Range, Stewardship Profile, Threats Posed by this Species, Biological Control, Research Needs, and more. Also at the site are lists of effective weed tools, weeds in the news, and links to weed-related events.

9

Weed Detection Using Canopy Reflection  

Microsoft Academic Search

For site-specific application of herbicides, automatic detection and evaluation of weeds is desirable. Since reflectance of crop, weeds and soil differs in the visual and near infrared wavelengths, there is potential for using reflection measurements at different wavelengths to distinguish between them. Reflectance spectra of crop and weed canopies were used to evaluate the possibilities of weed detection with reflection

E. Vrindts; J. De Baerdemaeker; H. Ramon

2002-01-01

10

Intercropping leeks to suppress weeds  

Microsoft Academic Search

Many field vegetables such as leek are weak competitors against weeds, causing high costs for weed management practice. Using celery as a companion cash crop was suggested to improve the weed suppression of leek. Three field experiments were carried out to study the intra- and interspecific competition in a leek:celery intercrop with and without additional weed competition. Results from this

D. T. Baumann; M. J. Kropff; L. Bastiaans

2000-01-01

11

Genomics for Weed Science  

PubMed Central

Numerous genomic-based studies have provided insight to the physiological and evolutionary processes involved in developmental and environmental processes of model plants such as arabidopsis and rice. However, far fewer efforts have been attempted to use genomic resources to study physiological and evolutionary processes of weedy plants. Genomics-based tools such as extensive EST databases and microarrays have been developed for a limited number of weedy species, although application of information and resources developed for model plants and crops are possible and have been exploited. These tools have just begun to provide insights into the response of these weeds to herbivore and pathogen attack, survival of extreme environmental conditions, and interaction with crops. The potential of these tools to illuminate mechanisms controlling the traits that allow weeds to invade novel habitats, survive extreme environments, and that make weeds difficult to eradicate have potential for both improving crops and developing novel methods to control weeds.

Horvath, David

2010-01-01

12

Controlling Aquatic Weeds.  

National Technical Information Service (NTIS)

The article discusses the increasing problem of aquatic weed growth along the New York coastal waters. At present some alternative solutions have been undertaken. Each control treatment method is discussed briefly but as of yet no definite course of actio...

M. Duttweiler

1975-01-01

13

Weed Problems and Weed Control in the Commonwealth Caribbean  

Microsoft Academic Search

The effect of weeds on crops is discussed, with particular reference to the Commonwealth Caribbean. The most serious weeds in the region are Cyperus rotundas, Cynodon dactylon, Commelina spp., Parthenium hysterophorus, Portulaca oleracea, Cleome spp. and Amaranthus spp. Serious weeds include Eleusine indica, Echinochloa colonum, Euphorbia spp., Brachiaria mutica, Paspalum conjugatum, Sporobolus indicus and Ipomoea tiliaceae. Brief notes are given

J. L. Hammerton

1981-01-01

14

Weeds and Fire  

NSDL National Science Digital Library

Students will locate some weed and native species found in Oregon and will understand that while databases are beneficial in studying plant populations, local on-the-ground information is commonly more up-to-date and that both are required to make large scale management decisions. Students will learn that the invasion of weeds commonly follows on the heels of a disturbance (natural or otherwise) and be introduced to some of the factors that impact the success of weeds in a particular ecosystem. Students will begin to relate the data to real-life situations and how they could be used to create management plans/strategies and/or alter existing management practices. This resource includes both a teaching guide and student worksheets.

Kenna, Sean

2011-09-15

15

Controlling Landscape Weeds.  

ERIC Educational Resources Information Center

This agriculture extension service publication from Pennsylvania State University discusses the control of common grass and broadleaf weeds through the use of mulches and herbicides. The section on mulches discusses the different types of mulching materials, their advantages and disadvantages, herbicide-mulch combinations, and lists source of…

Nuss, James Robert, Jr.

16

A Weed Cantilever  

ERIC Educational Resources Information Center

Describes the Environmental Action Task activity, which may be used as a recreational game or an environmental perception experience, may be conducted indoors or out-of-doors, using weed stems (or spaghetti) and masking tape to construct a cantilever. Small groups of children work together to make the cantilever with the longest arm. Further…

Keller, Elhannan L.; Padalino, John

1977-01-01

17

Weed Identification and Control in Vegetable Crops.  

ERIC Educational Resources Information Center

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…

Ferretti, Peter A., Comp.

18

Helping Pines Earn More with Weed Control.  

National Technical Information Service (NTIS)

The report concerns the preserving of forest pine through weed control. Various tables provide information on determining costs versus desired amount of weed control and level of weed competition that exists. A section discusses how the trees mentioned in...

C. W. Dangerfield H. L. Merck J. W. Taylor C. Redmond

1990-01-01

19

Weeding Library Collections: Library Weeding Methods. Fourth Edition.  

ERIC Educational Resources Information Center

Weeding is one of the best ways to make long-term improvements to library collections, but it is also a difficult and sometimes painful task. In the tradition of previous editions, this book guides librarians in the process of methodical and efficient weeding. The book shows how to identify core collections versus the weedable items. The approach…

Slote, Stanly J.

20

Weed Identification Field Training Demonstrations.  

ERIC Educational Resources Information Center

Reviews efforts undertaken in weed identification field training sessions for agriprofessionals in South Carolina. Data over a four year period (1980-1983) revealed that participants showed significant improvement in their ability to identify weeds. Reaffirms the value of the field demonstration technique. (ML)

Murdock, Edward C.; And Others

1986-01-01

21

Weed to Wonder  

NSDL National Science Digital Library

Human ingenuity never ceases! This wonderful website from the Cold Spring Harbor Laboratory tells the story of how a common Mexican weed (teosinte) was slowly manipulated by humans until it transformed into corn. As an introduction, users might want to start by watching a 2 minute and 50 second video of maize plants growing at Cold Spring Harbor Laboratory. After that, it's a good idea to look over the six separate sections here, which include Domestication, Hybrid Vigor, Genome Sequencing, and Jumping Genes. Each area contains explanatory text, photos, primary documents, and thoughtful explanations of complex scientific ideas.

2012-01-01

22

7 CFR 201.50 - Weed seed.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Weed seed. 201.50 Section 201.50 ...Administration of the Act § 201.50 Weed seed. Seeds (including bulblets or tubers) of plants shall be considered weed seeds when recognized as weed...

2009-01-01

23

Applicator Training Manual for: Aquatic Weed Control.  

ERIC Educational Resources Information Center

The aquatic weeds discussed in this manual include algae, floating weeds, emersed weeds, and submerged weeds. Specific requirements for pesticide application are given for static water, limited flow, and moving water situations. Secondary effects of improper application rates and faulty application are described. Finally, techniques of limited…

Herron, James W.

24

Weeding the School Library Media Collection.  

ERIC Educational Resources Information Center

This document prepared by Calgary Board of Education, Calgary, Alberta, Canada, discusses a systematic approach to strengthening the library media collection. A statement of principle, what to weed, specific guides to weeding (by Dewey Decimal classification and type of material), what not to weed, procedures, and weeding follow-up are…

School Library Media Quarterly, 1984

1984-01-01

25

7 CFR 201.50 - Weed seed.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Weed seed. 201.50 Section 201.50 ...Administration of the Act § 201.50 Weed seed. Seeds (including bulblets or tubers) of plants shall be considered weed seeds when recognized as weed...

2010-01-01

26

Can Global Weed Assemblages Be Used to Predict Future Weeds?  

PubMed Central

Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM) approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems.

Morin, Louise; Paini, Dean R.; Randall, Roderick P.

2013-01-01

27

Australian Weeds Research Newsletter No. 34, 1985.  

National Technical Information Service (NTIS)

The issue of the Newsletter comprises the latest revision of the Index of Australian Weeds Research Projects. The Index is regularly updated for the Australian Weeds Committee in an attempt to improve communication between scientists working in the many d...

G. J. Harvey

1985-01-01

28

The Weeding of a Historical Society Library.  

ERIC Educational Resources Information Center

Describes a major deaccessioning (weeding) project begun in 1985 at the library of the Nebraska State Historical Society, including a brief history of the Society and the events leading to the decision to weed. Public controversy over the handling of the project, benefits of the weeding, and new acquisitions policies are also discussed. (MES)

Drake, Cindy Steinhoff

1992-01-01

29

Using weeds to fight wastes  

SciTech Connect

Researchers at Los Alamos National Laboratory and New Mexico State University have discovered that jimson weed and wild tomato plants can remove the toxic wastes in wastewater associated with the production of trinitrotoluene (TNT). According to Wolfgang F. Mueller of New Mexico State, tissue-cultured cells of jimson weed rapidly absorb and break down toxic and carcinogenic elements in {open_quotes}pink water,{close_quotes} a by-product of the manufacture of TNT. Mueller and his colleagues have found similar results with the wild tomato plant.

NONE

1992-10-01

30

Colorado Weed Management Guide, 2004.  

National Technical Information Service (NTIS)

This guide is designed as a reference for weed management in various cropping systems and non-crop areas in Colorado. The information provided in this guide is not intended to be a complete guide to herbicide use. Before using any chemical, you should tho...

2004-01-01

31

The future for weed control and technology.  

PubMed

This review is both a retrospective (what have we missed?) and prospective (where are we going?) examination of weed control and technology, particularly as it applies to herbicide-resistant weed management (RWM). Major obstacles to RWM are discussed, including lack of diversity in weed management, unwillingness of many weed researchers to conduct real integrated weed management research or growers to accept recommendations, influence or role of agrichemical marketing and governmental policy and lack of multidisciplinary research. We then look ahead to new technologies that are needed for future weed control in general and RWM in particular, in areas such as non-chemical and chemical weed management, novel herbicides, site-specific weed management, drones for monitoring large areas, wider application of 'omics' and simulation model development. Finally, we discuss implementation strategies for integrated weed management to achieve RWM, development of RWM for developing countries, a new classification of herbicides based on mode of metabolism to facilitate greater stewardship and greater global exchange of information to focus efforts on areas that maximize progress in weed control and RWM. There is little doubt that new or emerging technologies will provide novel tools for RMW in the future, but will they arrive in time? © 2013 Her Majesty the Queen in Right of Canada Pest Management Science © 2013 Society of Chemical Industry. PMID:24339388

Shaner, Dale L; Beckie, Hugh J

2014-09-01

32

Weeds in Cotton: Their Biology, Ecology, and Control.  

National Technical Information Service (NTIS)

The publication brings together over 25 years of accmulated knowledge about the biology and ecology of weeds in cotton that growers can put to practical use in weed management. The weeds studied include three perennials (bermudagrass, johnsongrass, and ye...

P. E. Keeley R. J. Thullen

1993-01-01

33

Weed control strategies for grain legumes  

Microsoft Academic Search

There has been increasing interest in sustainable weed management in low-input farming systems. In an integrated approach,\\u000a the development of cropping systems such as appropriate spatial arrangement and efficient tillage will help crops themselves\\u000a to compete with weeds. With this aim, we investigated the strategic use of plant lodging combined with mechanical weed treatment\\u000a to improve crop competitiveness and reduce

G. Avola; R. Tuttobene; F. Gresta; V. Abbate

2008-01-01

34

N-Q Weed killer  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: A liquid weed-killer comes in four different bottles, all with the same active ingredient. The accompanying table gives information about the concentra...

35

The blossoms and the weeds.  

PubMed

As attested by the articles in this issue and the papers given at the festschrift, I have had the privilege of working with a talented group of people. In this article, a critique is given on the bouquet of themes that have bound many of us together, sorting the blossoms from some of the weeds. A brief description is then given of how these themes are working out in our current research on categorization. PMID:15832635

Brooks, Lee R

2005-03-01

36

Weeding Is Not Just for Gardeners: A Case Study on Weeding a Reference Collection  

ERIC Educational Resources Information Center

Weeding a reference collection can be time consuming, a thankless job, and an endless task. It is a dusty job and can add to the librarian's workload. Weeding the collection can add to its currency and usability; plus it removes outdated materials. Periodically weeding allows librarians to remember what is in the collection and what can be removed…

Lee, Marta

2009-01-01

37

Factors which facilitate waste water treatment by aquatic weeds – the mechanism of the weeds’ purifying action  

Microsoft Academic Search

Aquatic weeds such as water hyacinth, salvinia, pistia, and lemna have proved to be powerful bioagents which significantly purify wastewater lying under them. Even the performance of conventional oxidation ponds can be greatly enhanced by the simple expedient of introducing one of these aquatic weeds. Weeds absorb certain pollutants. But the contribution of absorption to the overall treatment is only

Tasneem Abbasi; S. A. Abbasi

2010-01-01

38

Successes in Biological Control of Weeds  

Microsoft Academic Search

There have been many successes world-wide in the biological control of weeds. Forty- one weeds are listed which have been successfully controlled using introduced agents (insects and pathogens) and a further three which are controlled using native fungi applied as mycoherbicides. Many of the successes have been repeated in subsequent programs in different countries or continents. Biological control programs have

R. E. CRUTTWELL MCFADYEN

39

Chemical weed control in seedbed sown onion ( Allium cepa L.)  

Microsoft Academic Search

Chemical control of weeds in seedbed sown onion (Allium cepa L. cv. Geza 20) and the effect of different herbicides on onion seedlings and weed growth were investigated in two field experiments conducted at the central Jordan Valley during the 1998\\/1999 growing season. Weed competition reduced average onion fresh yield by 62% compared with the weed-free control. Out of 14

J. R. Qasem

2006-01-01

40

Evaluation of integrated weed management practices for onion in Pakistan  

Microsoft Academic Search

Weed management studies in transplanted onion were conducted during 2004 and 2005 at the National Agricultural Research Centre, Islamabad, Pakistan. Pendimethalin and oxadiazon were applied post-emergence 2 days and 4 week after transplanting and their efficacy alone and in combination with one manual weeding was evaluated to reduce weed competition and its effects on marketable bulb yield. Hand weeded and

Khalid Mahmood Khokhar; Tariq Mahmood; Muhammad Shakeel; M. Farooq Chaudhry

2006-01-01

41

Optical weed detection and evaluation using reflection measurements  

Microsoft Academic Search

For the site-specific application of herbicides, the automatic detection and evaluation of weeds is necessary. Since reflectance of crop, weeds and soil differs in visual and near IR wavelengths, there is a potential for using reflection measurements at different wavelengths to distinguish between them. Diffuse reflectance spectra of crop and weed leaves were used to evaluate the possibilities of weed

Els Vrindts; Josse de Baerdemaeker

1999-01-01

42

Biological weed control with soil fungi? Antagonistic effects of arbuscular mycorrhizal fungi on the growth of weeds  

Microsoft Academic Search

Excessive weed growth represents one of the major threats to crop production especially when reliance on herbicides is reduced. Biological weed control is an alternative, environmentally-sound method that, combined with other weed control practices, can contribute to an effective weed management in sustainable farming systems. Arbuscular mycorrhizal fungi (AMF) are widespread soil fungi that form symbiotic associations with the majority

R. Veiga

2012-01-01

43

A study of weeding policies in eleven TALON resource libraries.  

PubMed Central

A study was made of the weeding policies and practices of eleven TALON resource libraries. The results indicated that although weeding, or collection evaluation as it is also known, was performed by most of the libraries, few had a written policy. The reasons for weeding and the types of weeding done by the libraries are described. A discussion of the prevalent means of disposition of withdrawn materials and of the obstacles to cooperative weeding is included.

Goldstein, C H

1981-01-01

44

Using Weeds and Wildflowers to Study Plants.  

ERIC Educational Resources Information Center

Offers suggestions for activities in which local weeds and wildflowers are used to study a variety of topics. These topics include classification, ecological succession, and mapping. Also lists the types of experiments students can perform with these plants. (JN)

Nowak, Nancy

1984-01-01

45

Wallowa Canyonlands Weed Partnership. Completion Report.  

National Technical Information Service (NTIS)

Noxious weeds threaten fish and wildlife habitat by contributing to increased sedimentation rates, diminishing riparian structure and function, and reducing forage quality and quantity. Wallowa Resources Wallowa Canyonlands Partnership (WCP) protects the ...

M. C. Porter S. Ketchum

2008-01-01

46

Global perspective of herbicide-resistant weeds.  

PubMed

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. PMID:24302673

Heap, Ian

2014-09-01

47

Weed Research in Sri Lanka: An Annotated Bibliography.  

National Technical Information Service (NTIS)

The annotated bibliography assembles information from the numerous studies on specific weed species and weed management methods that have been conducted in this country's annual and perennial crop sectors during the past several years. Surveys in lowland ...

H. P. M. Gunasena

1992-01-01

48

Weed Control of Growing Stands of Energy Forests.  

National Technical Information Service (NTIS)

Investigations that would lead to the selection of suitable methods of weed control in growing stands of energy forests were started. Different methods of accomplishing the weed control measures, i.e., both mechanical and chemical methods must be availabl...

O. Noren B. Danfors A. Stambeck

1983-01-01

49

An Ultrasonic System for Weed Detection in Cereal Crops  

PubMed Central

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.

Andujar, Dionisio; Weis, Martin; Gerhards, Roland

2012-01-01

50

Effect of tillage intensity on weed infestation in organic farming  

Microsoft Academic Search

Conservation tillage is not yet widely accepted by organic farmers because inversion tillage is considered to be necessary for weed control. Three long-term experiments were established with combinations of reduced and conventional plough tillage and stubble tillage to determine weed infestation levels in organic farming, i.e. herbicide application being excluded. Experiment 1 (with very low stocking density of perennial weeds)

Sabine Gruber; Wilhelm Claupein

2009-01-01

51

Postdispersal Weed Seed Predation Is Affected by Experimental Substrate  

Microsoft Academic Search

A standard method for evaluating weed seed predation is needed to facilitate generalizations across studies. Identification of general trends could allow practical recommendations for enhancing weed seed predation in agricultural systems. The objective of this study was to compare the commonly used sandpaper and soil substrate methods for offering weed seeds when assessing seed predation rates. Invertebrate seed predators and

Rachel E. Shuler; Antonio DiTommaso; John E. Losey; Charles L. Mohler

2008-01-01

52

Pest Control in Corn and Soybeans: Weeds - Insects - Diseases.  

ERIC Educational Resources Information Center

This document gives the characteristics and application rates for herbicides used to control annual weeds in corn, annual and perennial broadleaf weeds in corn, quackgrass and yellow nutsedge in corn, and annual weeds in soybeans. It also gives insecticide use information for corn and soybeans. A brief discussion of disease control in corn and…

Doersch, R. E.; And Others

53

A novel numerical optimization algorithm inspired from weed colonization  

Microsoft Academic Search

This paper introduces a novel numerical stochastic optimization algorithm inspired from colonizing weeds. Weeds are plants whose vigorous, invasive habits of growth pose a serious threat to desirable, cultivated plants making them a threat for agriculture. Weeds have shown to be very robust and adaptive to change in environment. Thus, capturing their properties would lead to a powerful optimization algorithm.

Ali Reza Mehrabian; Caro Lucas

2006-01-01

54

75 FR 68945 - Update of Noxious Weed Regulations  

Federal Register 2010, 2011, 2012, 2013

...requirements for permits to move noxious weeds in Sec. 360...requirements for permits to import or move noxious weeds. Proposed Sec...application for a permit to move a noxious weed when the Administrator...determined that, among other things, a State plant...

2010-11-10

55

Phenological observations on shrubs to predict weed emergence in turf  

Microsoft Academic Search

Phenology is the study of periodic biological events. If we can find easily recognizable events in common plants that precede or coincide with weed emergences, these plants could be used as indicators. Weed seedlings are usually difficult to detect in turf, so the use of phenological indicators may provide an alternative approach to predict the time when a weed appears

Roberta Masin; Maria Clara Zuin; Giuseppe Zanin

2005-01-01

56

7 CFR 201.52 - Noxious-weed seeds.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Noxious-weed seeds. 201.52 Section 201.52...Administration of the Act § 201.52 Noxious-weed seeds. (a) The determination of...bulblets, or tubers of individual noxious weeds present per unit weight should be...

2010-01-01

57

7 CFR 201.52 - Noxious-weed seeds.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Noxious-weed seeds. 201.52 Section 201.52...Administration of the Act § 201.52 Noxious-weed seeds. (a) The determination of...bulblets, or tubers of individual noxious weeds present per unit weight should be...

2009-01-01

58

Environmental control of dormancy in weed seed banks in soil  

Microsoft Academic Search

Dormancy is a common attribute of many weed seed populations and this usually hampers the task of predicting timing and extent of emergence of weeds. Both the number of established plants and the timing of emergence of a weed are strongly related to the dynamics of dormancy release of the seed population. In this paper, we discuss the different factors

Roberto L. Benech-arnold; Rodolfo A Sánchez; Frank Forcella; Betina C. Kruk; Claudio M. Ghersa

2000-01-01

59

Detecting Weed Infestations in Soybean Using Remote Sensing.  

NASA Astrophysics Data System (ADS)

Can weed distribution maps be developed from remote sensed reflectance data? When are the appropriate times to collect these data during the season? What wavebands can be used to distinguish weedy from weed- free areas? This research examined if and when reflectance could be used to distinguish between weed-free and weed-infested (mixed species) areas in soybean and to determine the most useful wavebands to separate crop, weed, and soil reflectance differences. Treatments in the two-year study included no vegetation (bare soil), weed-free soybean, and weed-infested soybean and, in one year, 80% corn residue cover. Reflectance was measured at several sampling times from May through September in 2001 and 2002 using a hand-held multispectral radiometer equipped with band-limited optical interference filters (460 - 1650 nm). Pixel resolution was 0.8-m. Reflectance in the visible spectral range (460 to 700 nm) generally was similar among treatments. In the near-infrared (NIR) range (>700 to 1650 nm), differences among treatments were observed from soybean growth stage V-3 (about 4 weeks after planting) until mid-July to early August depending on crop vigor and canopy closure (76 cm row spacing in 2001 and 19 cm row spacing in 2002). Reflectance rankings in the NIR range when treatments could be differentiated were consistent between years and, from lowest to highest reflectance, were soil < weed-free < weed-infested areas. Increased reflectance from weed-infested areas was most likely due to increased biomass and canopy cover. Residue masked differences between weed-free and weed- infested areas during the early stages of growth due to high reflectance from the residue and reduced weed numbers in these areas. These results suggest that NIR spectral reflectance collected prior to canopy closure can be used to distinguish weed-infested from weed-free areas.

Clay, S. A.; Chang, J.; Clay, D. E.; Dalsted, K.; Reese, C.

2007-12-01

60

Virus infection of a weed increases vector attraction to and vector fitness on the weed  

PubMed Central

Weeds are important in the ecology of field crops, and when crops are harvested, weeds often become the main hosts for plant viruses and their insect vectors. Few studies, however, have examined the relationships between plant viruses, vectors, and weeds. Here, we investigated how infection of the weed Datura stramonium L. by tomato yellow leaf curl virus (TYLCV) affects the host preference and performance of the TYLCV vector, Bemisia tabaci (Gennadius) Q. The results of a choice experiment indicated that B. tabaci Q preferentially settled and oviposited on TYLCV-infected plants rather than on healthy plants. In addition, B. tabaci Q performed better on TYLCV-infected plants than on healthy plants. These results demonstrate that TYLCV is indirectly mutualistic to B. tabaci Q. The mutually beneficial interaction between TYLCV and B. tabaci Q may help explain the concurrent outbreaks of TYLCV and B. tabaci Q in China.

Chen, Gong; Pan, Huipeng; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Fang, Yong; Shi, Xiaobin; Zhang, Youjun

2013-01-01

61

Weed hosts of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae).  

PubMed

The exotic cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) invaded India during 2006, and caused widespread infestation across all nine cotton growing states. P. solenopsis also infested weeds that aided its faster spread and increased severity across cotton fields. Two year survey carried out to document host plants of P. solenopsis between 2008 and 2010 revealed 27, 83, 59 and 108 weeds belonging to 8, 18, 10 and 32 families serving as alternate hosts at North, Central, South and All India cotton growing zones, respectively. Plant species of four families viz., Asteraceae, Amaranthaceae, Malvaceae and Lamiaceae constituted almost 50% of the weed hosts. While 39 weed species supported P. solenopsis multiplication during the cotton season, 37 were hosts during off season. Higher number of weeds as off season hosts (17) outnumbering cotton season (13) at Central over other zones indicated the strong carryover of the pest aided by weeds between two cotton seasons. Six, two and seven weed hosts had the extreme severity of Grade 4 during cotton, off and cotton + off seasons, respectively. Higher number of weed hosts of P. solenopsis were located at roadside: South (12) > Central (8) > North (3) zones. Commonality of weed hosts was higher between C+S zones, while no weed host was common between N+S zones. Paper furnishes the wide range of weed hosts of P. solenopsis, discusses their significance, and formulated general and specific cultural management strategies for nationwide implementation to prevent its outbreaks. PMID:24620572

Vennila, S; Prasad, Y G; Prabhakar, M; Agarwal, Meenu; Sreedevi, G; Bambawale, O M

2013-03-01

62

Australian Weeds Research Newsletter Number 33, 1985.  

National Technical Information Service (NTIS)

Contents: Effect of pre-plant 2,4-D on wheat and barley; Effect of soil type on the decline in emergence of four weed species; Leaching of hexazinone on hill slopes; Persistence and mobility of simazine under different soil and climatic conditions; Tolera...

G. J. Harvey

1985-01-01

63

The role of weeds in Niger  

Microsoft Academic Search

Livestock plays a key role in the traditional household economy of mixed-farming systems in Niger. During the rainy season, feed demands of animals can be satisfied by fresh grasses and herbaceous plants. At the onset of the dry season, animals prefer millet leaves and weeds to millet stalks. During the dry season feed is most limited due to the scarcity

John Lamers; Frank Emhard

64

Weed Science and Technology. MP-17.  

ERIC Educational Resources Information Center

This document is one in a series distributed by the Agricultural Extension Service of the University of Wyoming-Laramie. It presents the principles and methods of weed control especially as it relates to the use of herbicides. The factors influencing the effectiveness of both foliar-applied and soil-applied herbicides are discussed. A listing of…

Alley, Harold P.; Lee, Gary A.

65

Jimson "Loco" Weed Abuse in Adolescents.  

ERIC Educational Resources Information Center

Over a 3-year period, 29 adolescent patients were hospitalized because of intentional Jimson weed ingestion. Their records were reviewed for the presence of signs and symptoms of atropine/scopolamine toxicity, clinical course, treatment, and outcome. Journal availability: Arthur Retlaw and Associates, Inc., Suite 2080, 1603 Orrington Avenue,…

Shervette, Robert E., III; And Others

1979-01-01

66

Chloropicrin effect on weed seed viability  

Microsoft Academic Search

Chloropicrin is a potential replacement for methyl bromide as a preplant soil fumigant. Its weed control efficacy was evaluated in a laboratory dose–response study and in a commercial strawberry field. Laboratory studies found that an increase in chloropicrin concentration and exposure time reduced the percentage of viable Stellaria media (L.) Mill., Portulaca oleracea L. and Polygonum aviculare L. seed. Chloropicrin

M. J. Haar; S. A. Fennimore; H. A. Ajwa; C. Q Winterbottom

2003-01-01

67

7 CFR 360.300 - General prohibitions and restrictions on the movement of noxious weeds; permits.  

Code of Federal Regulations, 2010 CFR

...restrictions on the movement of noxious weeds; permits. 360.300 Section 360...SERVICE, DEPARTMENT OF AGRICULTURE NOXIOUS WEED REGULATIONS § 360.300 General prohibitions...restrictions on the movement of noxious weeds; permits. (a) No person may...

2010-01-01

68

7 CFR 360.300 - General prohibitions and restrictions on the movement of noxious weeds; permits.  

Code of Federal Regulations, 2010 CFR

...restrictions on the movement of noxious weeds; permits. 360.300 Section 360...SERVICE, DEPARTMENT OF AGRICULTURE NOXIOUS WEED REGULATIONS § 360.300 General prohibitions...restrictions on the movement of noxious weeds; permits. (a) No person may...

2009-01-01

69

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

Code of Federal Regulations, 2010 CFR

... 2009-01-01 false Crop pest, weed, and disease management practice standard...Requirements § 205.206 Crop pest, weed, and disease management practice standard...management practices to prevent crop pests, weeds, and diseases including but not...

2009-01-01

70

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

Code of Federal Regulations, 2010 CFR

... 2010-01-01 false Crop pest, weed, and disease management practice standard...Requirements § 205.206 Crop pest, weed, and disease management practice standard...management practices to prevent crop pests, weeds, and diseases including but not...

2010-01-01

71

Evaluation of mulching, stale seedbed, hand weeding and hoeing for weed control in organic garden pea (Pisum sativum sub sp. Hortens L.)  

Microsoft Academic Search

Weeds are often recognized as the principal biotic constraint to organic crop production. Development of suitable weed control measures is, therefore, a prerequisite for profitable organic farming. A field experiment was conducted during the winter season of 2003–2004 and 2004–2005 in the Indian Himalayas to evaluate the effect of mulching, stale seedbed, hand weeding and hoeing on weeds and yield

K. A. Gopinath; Narendra Kumar; Banshi L. Mina; Anil K. Srivastva; H. S. Gupta

2009-01-01

72

Evaluation of integrated weed management practices for chilies in Pakistan  

Microsoft Academic Search

Weed management studies in transplanted chilies were conducted during 2004 and 2005 at the National Agricultural Research Centre, Islamabad, Pakistan. Pendimethalin and oxadiazon at 0.825 and 0.240l a.i.ha?1, respectively were applied 1 week before and 2 days after transplanting and their efficacy alone and in combination with one manual weeding was evaluated to reduce weed competition and its effects on

Khalid Mahmood Khokhar; Tariq Mehmood; Muhammad Shakeel

2007-01-01

73

Chemical weed control in garlic ( Allium sativum L.) in Jordan  

Microsoft Academic Search

Field experiments were made in 1992 and 1993 in different locations to study the effect of certain herbicides on weed control in garlic. Post-emergence application of oxyfluorfen and oxadiazon at 3–4 leaf stage resulted in garlic yield comparable to the weed-free crop. Pre-plant application of both herbicides was also effective in weed control and increased garlic yield over the other

J. R. Qasem

1996-01-01

74

Developing selection protocols for weed competitiveness in aerobic rice  

Microsoft Academic Search

Aerobic rice production systems, wherein rice is dry-sown in non-puddled soil and grown as an upland crop, offer large water savings but are subject to severe weed infestation. Weed-competitive cultivars will be critical to the adoption of aerobic rice production by farmers. Breeding weed-competitive cultivars requires an easily used selection protocol, preferably based on traits that can be measured under

D. L. Zhao; G. N. Atlin; L. Bastiaans; J. H. J. Spiertz

2006-01-01

75

Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds?  

PubMed Central

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.

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

2011-01-01

76

Critical period of weed control in aerobic rice.  

PubMed

Critical period of weed control is the foundation of integrated weed management and, hence, can be considered the first step to design weed control strategy. To determine critical period of weed control of aerobic rice, field trials were conducted during 2010/2011 at Universiti Putra Malaysia. A quantitative series of treatments comprising two components, (a) increasing duration of weed interference and (b) increasing length of weed-free period, were imposed. Critical period was determined through Logistic and Gompertz equations. Critical period varied between seasons; in main season, it started earlier and lasted longer, as compared to off-season. The onset of the critical period was found relatively stable between seasons, while the end was more variable. Critical period was determined as 7-49 days after seeding in off-season and 7-53 days in main season to achieve 95% of weed-free yield, and 23-40 days in off-season and 21-43 days in main season to achieve 90% of weed-free yield. Since 5% yield loss level is not practical from economic view point, a 10% yield loss may be considered excellent from economic view point. Therefore, aerobic rice should be kept weed-free during 21-43 days for better yield and higher economic return. PMID:22778701

Anwar, M P; Juraimi, A S; Samedani, B; Puteh, A; Man, A

2012-01-01

77

Weed seed viability in composted beef cattle feedlot manure.  

PubMed

Manure composting has gained increased acceptance by the beef cattle (Bos taurus) feedlot industry in southern Alberta, Canada. Unlike fresh manure, compost is often promoted as being "weed-free." Studies were conducted with five weed species in 1997 and thirteen in 1999 to examine the effect of feedlot manure composting on weed seed viability. Weed seeds were buried in open-air compost windrows and recovered at various times during the thermophilic phase of composting. Windrow temperature and water contents were also measured. Germinability was zero for all composted weed seeds at all sampling times in 1997. However, some seeds remained viable (positive tetrazolium test denoting respiration) on Day 70. In 1999, only one of the thirteen species retained germinability on Day 21 and only two species had respiring seeds on Day 42. Time-viability relationships during composting were defined by exponential decay models. Lethal temperatures to eliminate viability was species-dependent. In 1999, four weed species were killed in the initial 7 d of composting at a lethal temperature of 39 degrees C while temperatures of > 60 degrees C were required for two species. Regression analysis on weed seed viability versus windrow temperature resulted in significant R2 values, which showed that only 17 to 29% of the variation in viability was accounted for by temperature. The lack of definitive relationships between temperature and weed seed viability demonstrated that factors other than temperature may play a role in eliminating weed seeds during composting. PMID:12809312

Larney, Francis J; Blackshaw, Robert E

2003-01-01

78

Inter-Row Cultivation in Weed-Free Carrots: the Effect on Yield of Hoeing and Brush Weeding  

Microsoft Academic Search

Inter-row cultivation close to the row makes it possible to reduce the application of thermal or chemical weed control and also to save labour costs for hand weeding. Apart from the weed effect, inter-row tillage may also increase available water and nitrogen in the soil, affect soil temperature and crop roots. Three experiments were conducted in southern Sweden during 1988–1991,

Johan Ascard; Berit Mattsson

1994-01-01

79

Phytotoxicity of sesquiterpene lactone parthenin on aquatic weeds  

Microsoft Academic Search

The sesquiterpene lactone parthenin, one of the major toxins in an obnoxious weed, parthenium (Parthenium hysterophorus L.), was toxic at 50 ppm to the floating aquatic weeds pistia (Pistia stratiotes L.) and lemna (Lemna pausicostata Hegelm.) and at 100 ppm to water hyacinth (Eichhornia crassipes Mart Solmns.), salvinia (Salvinia molesta Mitchell), azolla (Azolla nilotica Decne.), and spirodella (Spirodella polyrhiza L.

D. K. Pandey

1996-01-01

80

Letting Go: How One Librarian Weeded a Children's Magazine Collection.  

ERIC Educational Resources Information Center

Describes the weeding process for children's magazines in a public library. Highlights include circulation statistics; cost effectiveness; online availability; shelving magazines by subject to try and increase their use; and a chart that lists reasons to keep and reasons to cancel subscriptions when weeding a periodical collection. (LRW)

Bromann, Jennifer

2002-01-01

81

Weed control by herbicides in cole crops and cucurbitaceous crops  

Microsoft Academic Search

In studies on chemical weed control in cole and cucurbitaceous crops, oxyfluorfen ('Goal') and fluchloralin ('Basalin') proved to be effective herbicides for transplanted cabbage and cauliflower, both in terms of reduced weed dry matter and increased crop yield. For pumpkin, squash and watermelon, butachlor at 2 kg a.i. ha proved to be a suitable herbicide. A significant increase in yield

D. Leela

1985-01-01

82

HERBICIDE COMBINATIONS FOR WEED CONTROL IN SKYLINE HONEYLOCUST1  

Microsoft Academic Search

2 Abstract. Pre-emergent fall applications of alachlor (Lasso) and oxadiazon (Ronstar) singly or in combination with linuron (Lorox) or simazine (Princep) exhibited in some cases ex- cellent weed control in excess of 9 months in a Skyline honeylocust planting. Alachlor when applied at the 6.0 Ib AIA (active ingredient per acre) rate controlled annual grass weeds 10 months after application.

Steven C. Prochaska; Thomas A. Fretz

83

CHANGES IN WEED SPECIES SPECTRUM IN RELATION TO SOIL TILLAGE  

Microsoft Academic Search

Summary Long-term experiments were conducted to study the effect of minimum tillage and conventional ploughing on annual weeds and on Elytrigia repens and Cirsium arvense. The evaluation of experiments since 1998 was aimed at a monitoring of increases in weed infestation for 5 years. The effect of minimum tillage compared to conventional ploughing with herbicide applications was investigated. The herbicides

Jan MIKULKA; Marta KNEIFELOVÁ

84

Biological control of neotropical aquatic weeds with fungi  

Microsoft Academic Search

Many of the world's worst tropical aquatic weeds are native to the Neotropics. Besides, the majority of the most aggressive aquatic weeds in that vast region of the world are endemic and therefore there is a need for exploration for biological control agents in that area. Entomologists had an early lead on this search. Only in the late 1970s did

R Barreto; R Charudattan; A Pomella; R Hanada

2000-01-01

85

WEED MANAGEMENT IN RICE BASED ZERO TILLED SOWN WHEAT  

Microsoft Academic Search

A field experiment was conducted at Research Farm of Directorate of Plant Protection, Quarantine and Storage, Faridabad, Haryana, India to study the weeds spectrum and weed control efficacy of different herbicides and their combinations in zero tilled sown wheat during 2003-04 and 2004-05. The experiment was laid out in a randomized complete block (RCB) design with three replications. During both

Moolchand Singh; P. S. Chandurkar; Arun Kumar

86

How to Identify and Control Water Weeds and Algae.  

ERIC Educational Resources Information Center

Included in this guide to water management are general descriptions of algae, toxic algae, weed problems in lakes, ponds, and canals, and general discussions of mechanical, biological and chemical control methods. In addition, pictures, descriptions, and recommended control methods are given for algae, 6 types of floating weeds, 18 types of…

Applied Biochemists, Inc., Mequon, WI.

87

Working the Educational Soil and Pulling Up Weeds  

ERIC Educational Resources Information Center

The job of an instructional leader, according to former Baltimore principal Deborah Wortham, is to be a gardener. School cultures left unattended, she says, sprout weeds that will eventually overwhelm the research-based programs, practices, and best efforts of teachers and administrators. The most aggressive and harmful educational weeds Wortham…

Riggins-Newby, Cheryl

2005-01-01

88

'Carolina' session: a major utilities program to manage aquatic weeds  

SciTech Connect

Carolina Power and Light Company has recently experienced aquatic weed problems in two of its impoundments. These problems have impacted power plant operations, water quality, and recreational activities. The Company is actively pursuing a program to deal with these weed problems through education, research, monitoring, and control activities.

Schiller, D.H.

1984-06-01

89

Optimal weed management in crop rotations: incorporating economics is crucial  

Microsoft Academic Search

Although the effects of crop rotation sequence and length on weed population dynamics have been studied, it is not clear whether or not the best strategy, from a weed population dynamics point of view, is also the economic optimal strategy. It is also not clear which biological and economic parameters are most important in determining this optimal strategy. We use

Berg van den F; C. A. Gilligan; J. C. Gerdessen; L. A. H. Gregoire; Bosch van den F

2010-01-01

90

Earthworms and weed seed distribution in annual crops  

Microsoft Academic Search

A field study was conducted to determine if earthworm activity would affect the abundance and composition of weed seed banks in annual row-crops. The abundance of weed seeds in surface-deposited earthworm casts was determined in continuous monocultures and rotations that included corn, soybean, and winter wheat, with or without cover crop. Casts were collected weekly over the growing season and

R. G. Smith; K. L. Gross; S. Januchowski

2005-01-01

91

Weed Suppression by Seven Clover Species  

SciTech Connect

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 treatments 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.

Ross, Shirley M.; King, Jane R.; Izaurralde, R Cesar C.; O'Donovan, John T.

2001-01-01

92

Natural compounds for pest and weed control.  

PubMed

The control of insect pests and invasive weeds has become more species-selective because of activity-guided isolation, structure elucidation, and total synthesis of naturally produced substances with important biological activities. Examples of isolated compounds include insect pheromones, antifeedants, and prostaglandins, as well as growth regulators for plants and insects. Synthetic analogues of natural substances have been prepared to explore the relationships between chemical structure and observed biological activity. Recent scientific advances have resulted from better methods for the chemical synthesis of target compounds and better analytical methods. The capability of analytical instrumentation continues to advance rapidly, enabling new insights. PMID:19719128

Petroski, Richard J; Stanley, David W

2009-09-23

93

Herbicide-Resistant Grass Weed Development in Imidazolinone-Resistant Wheat: Weed Biology and Herbicide Rotation 1  

Microsoft Academic Search

A general life cycle model was modified to demonstrate how agronomic practices and weed biology factors affect the rate of appearance of herbicide-resistant downy brome, jointed goat- grass, and wild oat in Pacific Northwest wheat cropping systems. The model suggests herbicide rotation strategies for cropping systems that include imidazolinone-resistant wheat as a weed man- agement tool. Simulation of continuous annual

CURTIS R. RAINBOLT; DONALD C. THILL; JOSEPH P. YENISH; DANIEL A. BALL

2004-01-01

94

The Identification, Distribution, Impacts, Biology and Management of Noxious Rangeland Weeds  

Microsoft Academic Search

This document provides a discussion of the biology and management of exotic rangeland weeds which are a threat to native ecosystems of the western United States. Chapter 1 describes a generalized approach for managing noxious weed infested rangeland, while Chapter 2 focuses on preventing noxious weed invasion. In some cases, noxious weeds readily invade riparian areas, and because of the

Roger L. Sheley

1994-01-01

95

Lawn Weeds and Their Control. North Central Regional Extension Publication No. 26.  

ERIC Educational Resources Information Center

This publication discusses lawn weed control for the twelve state north central region of the country. Written for use by homeowners, the publication focuses on weed identification and proper herbicide selection and application. Identification of weeds and safe and appropriate herbicide use are emphasized. Forty-six weed and turf plants are…

Purdue Univ., Lafayette, IN. Cooperative Extension Service.

96

Allelopathic influence of Sorghum bicolor on weeds during germination and early development of seedlings  

Microsoft Academic Search

The allelopathic interaction between sorghum [Sorghum bicolor (L.) Moench] and 10 species of grass and broadleaf weeds was investigated. Germination of weed seeds was slightly inhibited or stimulated, depending on species, when incubated in closed Petri dishes with germinating sorghum. Subsequent radicle and hypocotyl or coleoptile elongation of weeds was significantly inhibited by the germinating sorghum. For weeds interplanted with

Oksana Panasiuk; Donald D. Bills; Gerald R. Leather

1986-01-01

97

Wallowa Canyonlands Weed Partnership : Completion Report November 19, 2009  

SciTech Connect

Noxious weeds threaten fish and wildlife habitat by contributing to increased sedimentation rates, diminishing riparian structure and function, and reducing forage quality and quantity. Wallowa Resources Wallowa Canyonlands Partnership (WCP) protects the unique ecological and economic values of the Hells Canyon grasslands along lower Joseph Creek, the lower Grande Ronde and Imnaha Rivers from invasion and degradation by noxious weeds using Integrated Weed Management techniques. Objectives of this grant were to inventory and map high priority weeds, coordinate treatment of those weeds, release and monitor bio-control agents, educate the public as to the dangers of noxious weeds and how to deal with them, and restore lands to productive plant communities after treatment. With collaborative help from partners, WCP inventoried {approx} 215,000 upland acres and 52.2 miles of riparian habitat, released bio-controls at 23 sites, and educated the public through posters, weed profiles, newspaper articles, and radio advertisements. Additionally, WCP used other sources of funding to finance the treatment of 1,802 acres during the course of this grant.

Porter, Mark C.; Ketchum, Sarah

2008-12-30

98

Effect on Weed Growth of Short-Term Cover over Organically Grown Carrots  

Microsoft Academic Search

The effect on weeds and crop yield of a short-term polypropylene cover as a protection against carrot fly (Psila rosae) damage to organically grown carrots was assessed. Crops were hand-weeded prior to cover and then subjected to one of three weeding treatments during the covered period: none, one or two weedings. Total weed weight was greater with covered, versus non-covered,

L. Peacock

1991-01-01

99

Capabilities of unmanned aircraft vehicles for low altitude weed detection  

NASA Astrophysics Data System (ADS)

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.

Pflanz, Michael; Nordmeyer, Henning

2014-05-01

100

Noxious Weeds in the U.S. and Canada  

NSDL National Science Digital Library

This web site provides a searchable database of the noxious weed lists for all U.S. states and six southern provinces of Canada. The database can be searched by plant name, state name, or by clicking on a map. The search can be narrowed down to search for native, exotic, or all species of plants for a particular county. Furthermore, the search can be conducted for the time period that the user chooses. A summary of this database provides a list of all noxious weeds, which can be customized to display in alphabetical order (on scientific name) or by the number of appearances on weed lists.

101

Control of aquatic weeds through pollutant reduction and weed utilization: a weed management approach in the lower Kafue River of Zambia  

NASA Astrophysics Data System (ADS)

The aquatic weed situation in the Kafue River in Zambia continues to be a major challenge to the sustainable utilization of the water resources of the river. The general methods for managing the weeds, especially the water hyacinth, include use of bio-agents, chemicals, mechanical and physical approaches. These have had very little impact. This paper reports on a project that is investigating weed management strategies which involve use of cleaner production (CP) approach and the utilization of the weed for economic purposes. In addition, the ecological implications of these methods are being assessed. Effluent assessments indicated that apart from nitrates and phosphates, other effluent parameters met the Environmental Council of Zambia standards. Results further show that all the 24 areas surveyed for CP have uncontrolled socio-economic activities which generate both point and non-point sources of pollution that enter the water bodies. To minimize pollution, efforts include devising policy and technical strategies with the involvement of the affected riparian community. Production of mushroom by the communities using the water hyacinth substrate has been demonstrated. Up to 2.1 kg of mushroom was harvested from a single flush over a period of 4-5 weeks. Vegetables grown on soils treated with water hyacinth manure performed better than those grown using commercial fertiliser. The economics of the production are however, yet to be confirmed. If weed usage is proven economically and ecologically viable, the riverine community is envisaged to play a big role in aquatic weed management. High numbers of invertebrates known to be sensitive to pollution have been recorded in the weed-infested Kafue River implying that the water is of “good” quality for these aquatic invertebrates. This observed quality of water may be due to water hyacinth playing a role by sieving pollutants from the river.

Sinkala, Thomson; Mwase, Enala T.; Mwala, Mick

102

Appearance of Herbicide Resistance in a Weed Population  

NSDL National Science Digital Library

Through the repeated use of the same herbicide, weed populations can consist of susceptible (S)-biotypes that are controlled and herbicide resistant (R)-biotypes that are left behind to produce and return seed with the resistance characteristic back into the soil. This lesson will highlight the population dynamics of a mixed weed population, containing S- and R-biotypes, and compare and contrast the rate at which herbicide resistant weeds appear in a population under a diversity of selection pressures. This lesson will highlight the population dynamics of a mixed (herbicide susceptible and resistant biotype) weed population, and compare and contrast the rate of appearance of herbicide resistance in a mixed population under a diversity of selection pressures.

103

Weed Control Sprayers: Calibration and Maintenance. Special Circular 81.  

ERIC Educational Resources Information Center

This manual covers aspects of calibration and maintenance of weed control sprayers including variables affecting application rate, the pre-calibration check, calculations, band spraying, nozzle tip selection, agitation, and cleaning. (BB)

Myers, Arthur L.

104

Changes in the Weed Seedbank Following Different Weeding Treatments in Drilled Salad Onion and Carrot Crops Grown in Organic and Conventional Systems  

Microsoft Academic Search

Changes in the soil weed seedbank were monitored over a single growing season in field experiments with drilled salad onion and carrot crops following different weeding treatments. Viable weed seed numbers were determined in soil samples taken at crop sowing and at harvest. When the crops were left weedy until harvest, seed numbers in soil increased by between two- and

W. Bond; H. C. Moore; R. J. Atkinson; J. R. Bevan; M. E. K. Lennartsson

1998-01-01

105

The biology of habitat dominance; can microbes behave as weeds?  

PubMed Central

Summary Competition between microbial species is a product of, yet can lead to a reduction in, the microbial diversity of specific habitats. Microbial habitats can resemble ecological battlefields where microbial cells struggle to dominate and/or annihilate each other and we explore the hypothesis that (like plant weeds) some microbes are genetically hard-wired to behave in a vigorous and ecologically aggressive manner. These ‘microbial weeds’ are able to dominate the communities that develop in fertile but uncolonized – or at least partially vacant – habitats via traits enabling them to out-grow competitors; robust tolerances to habitat-relevant stress parameters and highly efficient energy-generation systems; avoidance of or resistance to viral infection, predation and grazers; potent antimicrobial systems; and exceptional abilities to sequester and store resources. In addition, those associated with nutritionally complex habitats are extraordinarily versatile in their utilization of diverse substrates. Weed species typically deploy multiple types of antimicrobial including toxins; volatile organic compounds that act as either hydrophobic or highly chaotropic stressors; biosurfactants; organic acids; and moderately chaotropic solutes that are produced in bulk quantities (e.g. acetone, ethanol). Whereas ability to dominate communities is habitat-specific we suggest that some microbial species are archetypal weeds including generalists such as: Pichia anomala, Acinetobacter spp. and Pseudomonas putida; specialists such as Dunaliella salina, Saccharomyces cerevisiae, Lactobacillus spp. and other lactic acid bacteria; freshwater autotrophs Gonyostomum semen and Microcystis aeruginosa; obligate anaerobes such as Clostridium acetobutylicum; facultative pathogens such as Rhodotorula mucilaginosa, Pantoea ananatis and Pseudomonas aeruginosa; and other extremotolerant and extremophilic microbes such as Aspergillus spp., Salinibacter ruber and Haloquadratum walsbyi. Some microbes, such as Escherichia coli, Mycobacterium smegmatis and Pseudoxylaria spp., exhibit characteristics of both weed and non-weed species. We propose that the concept of nonweeds represents a ‘dustbin’ group that includes species such as Synodropsis spp., Polypaecilum pisce, Metschnikowia orientalis, Salmonella spp., and Caulobacter crescentus. We show that microbial weeds are conceptually distinct from plant weeds, microbial copiotrophs, r-strategists, and other ecophysiological groups of microorganism. Microbial weed species are unlikely to emerge from stationary-phase or other types of closed communities; it is open habitats that select for weed phenotypes. Specific characteristics that are common to diverse types of open habitat are identified, and implications of weed biology and open-habitat ecology are discussed in the context of further studies needed in the fields of environmental and applied microbiology.

Cray, Jonathan A; Bell, Andrew N W; Bhaganna, Prashanth; Mswaka, Allen Y; Timson, David J; Hallsworth, John E

2013-01-01

106

Cover crop residue management for optimizing weed control  

Microsoft Academic Search

Although residue management seems a key factor in residue-mediated weed suppression, very few studies have systematically\\u000a compared the influence of different residue management strategies on the establishment of crop and weed species. We evaluated\\u000a the effect of several methods of pre-treatment and placement of winter rye (Secale cereale L.) and winter oilseed rape (Brassica napus L.) residue on seedling emergence

H. Marjolein Kruidhof; Lammert Bastiaans; Martin J. Kropff

2009-01-01

107

Chemical and cultural weed control studies in cotton  

Microsoft Academic Search

Investigations were carried out to test the efficacy of several more recently developed selective herbicides, by comparison with hand?hoeing, for weed control and influence on seed yield in cotton. It was observed that hand?weeding at 30 days after sowing, followed by applications of granular oxadiazon with first irrigation in doses of 0.5, 1.0 or 1.5 kg a.i.\\/ha, proved as effective

R. S. Balyan; V. M. Bhan; S. P. Singh

1983-01-01

108

Fusing 3D Information for Crop\\/Weeds Classification  

Microsoft Academic Search

The main goal of this work is to construct a 3D-world map to help to distinguish between crop and weeds and finally to permit the location of crop and weeds to apply a variable treatment. To solve the problem of recovering a 3D-local map, we use a motion technique with the possibility of changing zoom. Every independent local map will

A. J. Sánchez; John A. Marchant

2000-01-01

109

Herbicide-resistant crops and weed resistance to herbicides.  

PubMed

The adoption of genetically modified (GM) crops has increased dramatically during the last 3 years, and currently over 52 million hectares of GM crops are planted world-wide. Approximately 41 million hectares of GM crops planted are herbicide-resistant crops, which includes an estimated 33.3 million hectares of herbicide-resistant soybean. Herbicide-resistant maize, canola, cotton and soybean accounted for 77% of the GM crop hectares in 2001. However, sugarbeet, wheat, and as many as 14 other crops have transgenic herbicide-resistant cultivars that may be commercially available in the near future. There are many risks associated with the production of GM and herbicide-resistant crops, including problems with grain contamination, segregation and introgression of herbicide-resistant traits, marketplace acceptance and an increased reliance on herbicides for weed control. The latter issue is represented in the occurrence of weed population shifts, the evolution of herbicide-resistant weed populations and herbicide-resistant crops becoming volunteer weeds. Another issue is the ecological impact that simple weed management programs based on herbicide-resistant crops have on weed communities. Asiatic dayflower (Commelina cumminus L) common lambsquarters (Chenopodium album L) and wild buckwheat (Polygonum convolvulus L) are reported to be increasing in prominence in some agroecosystems due to the simple and significant selection pressure brought to bear by herbicide-resistant crops and the concomitant use of the herbicide. Finally, evolution of herbicide-resistant weed populations attributable to the herbicide-resistant crop/herbicide program has been observed. Examples of herbicide-resistant weeds include populations of horseweed (Conyza canadensis (L) Cronq) resistant to N-(phosphonomethyl)glycine (glyphosate). An important question is whether or not these problems represent significant economic issues for future agriculture. PMID:15668920

Owen, Micheal D K; Zelaya, Ian A

2005-03-01

110

[Spatial and temporal dynamics of the weed community in the Zoysia matrella lawn].  

PubMed

The heterogeneity of species composition is one of the main attributes in weed community dynamics. Based on species frequency and power law, this paper studied the variations of weed community species composition and spatial heterogeneity in a Zoysia matrella lawn in Guangzhou at different time. The results showed that there were 43 weed species belonging to 19 families in the Z. matrella lawn from 2007 to 2009, in which Gramineae, Compositae, Cyperaceae and Rubiaceae had a comparative advantage. Perennial weeds accounted for the largest proportion of weeds and increased gradually in the three years. Weed communities distributed in higher heterogeneity than in a random model. Dominant weeds varied with season and displayed regularity in the order of 'dicotyledon-monocotyledon-dicotyledon weeds' and 'perennial-annual-perennial weeds'. The spatial heterogeneity of weed community in Z. matrella lawn was higher in summer than in winter. The diversity and evenness of weed community were higher in summer and autumn than in winter and spring. The number of weed species with high heterogeneity in summer was higher than in the other seasons. The spatial heterogeneity and diversity of weed community had no significant change in the three years, while the evenness of weed community had the tendency to decline gradually. PMID:24830239

Liu, Jia-Qi; Li, You-Han; Zeng, Ying; Xie, Xin-Ming

2014-02-01

111

36 CFR 222.8 - Cooperation in control of estray or unbranded livestock, animal diseases, noxious farm weeds, and...  

Code of Federal Regulations, 2013 CFR

...livestock, animal diseases, noxious farm weeds, and use of pesticides. 222.8 Section...livestock, animal diseases, noxious farm weeds, and use of pesticides. (a) Insofar...diseases, sanitation and noxious farm weeds. (2) The Animal and Plant...

2013-07-01

112

Tillage and residue burning affects weed populations and seed banks.  

PubMed

An integrated weed management approach requires alternative management practices to herbicide use such as tillage, crop rotations and cultural controls to reduce soil weed seed banks. The objective of this study was to examine the value of different tillage practices and stubble burning to exhaust the seed bank of common weeds from the northern grain region of Australia. Five tillage and burning treatments were incorporated in a field experiment, at Armidale (30 degrees 30'S, 151 degrees 40'E), New South Wales, Australia in July 2004 in a randomized block design replicated four times. The trial was continued and treatments repeated in July 2005 with all the mature plants from the first year being allowed to shed seed in their respective treatment plots. The treatments were (i) no tillage (NT), (ii) chisel ploughing (CP), (iii) mould board ploughing (MBP), (iv) wheat straw burning with no tillage (SBNT) and (v) wheat straw burning with chisel ploughing (SBC). Soil samples were collected before applying treatments and before the weeds flowered to establish the seed bank status of the various weeds in the soil. Wheat was sown after the tillage treatments. Burning treatments were only initiated in the second year, one month prior to tillage treatments. The major weeds present in the seed bank before initiating the trial were Polygonum aviculare, Sonchus oleraceus and Avena fatua. Tillage promoted the germination of other weeds like Hibiscus trionum, Medicago sativa, Vicia sp. and Phalaris paradoxa later in the season in 2004 and Convolvulus erubescens emerged as a new weed in 2005. The MBP treatment in 2004 reduced the weed biomass to a significantly lower level of 55 g/m2 than the other treatments of CP (118 g/m2) and NT plots (196 g/m2) (P < 0.05). However, in 2005 SBC and MBP treatments were similar in reducing the weed biomass. In 2004, the grain yield trend of wheat was significantly different between CP and NT, and MBP and NT (P < 0.05) with maximum yield of 5898 kg/ha in CP and 5731 kg/ha in MBP. Rainfall before the start of the second trial season promoted the germination of a large numbers of weeds. SBC and MBP treatments reduced the numbers of most of the individual weed species compared with CP, SBNT and NT. SBC was able to destroy a large proportion of seeds most likely through burning and burying some in the soil and was found to be the best treatment in exhausting the seed bank followed closely by MBP which probably buried large number of seeds deep in the soil and promoted others to germinate. CP might have buried some of the seeds in the top 5-10 cm but also promoted parts of the seed bank to germinate. SBNT and NT provided an ideal medium for weeds to germinate and resulted in heavy infestations of weeds. PMID:17390813

Narwal, S; Sindel, B M; Jessop, R S

2006-01-01

113

Natural metabolites for parasitic weed management.  

PubMed

Compounds of natural origin, such as phytotoxins produced by fungi or natural amino acids, could be used in parasitic weed management strategies by interfering with the early growth stages of the parasites. These metabolites could inhibit seed germination or germ tube elongation, so preventing attachment to the host plant, or, conversely, stimulate seed germination in the absence of the host, contributing to a reduction in the parasite seed bank. Some of the fungal metabolites assayed were very active even at very low concentrations, such as some macrocyclic trichothecenes, which at 0.1 microM strongly suppressed the germination of Orobanche ramosa L. seeds. Interesting results were also obtained with some novel toxins, such as phyllostictine A, highly active in reducing germ tube elongation and seed germination both of O. ramosa and of Cuscuta campestris Yuncker. Among the amino acids tested, methionine and arginine were particularly interesting, as they were able to suppress seed germination at concentrations lower than 1 mM. Some of the fungal metabolites tested were also able to stimulate the germination of O. ramosa seeds. The major findings in this research field are described and discussed. PMID:19266492

Vurro, Maurizio; Boari, Angela; Evidente, Antonio; Andolfi, Anna; Zermane, Nadjia

2009-05-01

114

75 FR 23151 - Noxious Weeds; Old World Climbing Fern and Maidenhair Creeper  

Federal Register 2010, 2011, 2012, 2013

...APHIS-2008-0097] Noxious Weeds; Old World Climbing Fern and Maidenhair Creeper AGENCY...noxious weed regulations by adding Old World climbing fern (Lygodium microphyllum...we amended the regulations by adding Old World climbing fern (Lygodium...

2010-05-03

115

Utility of remote sensing for soybean and weed species differentiation  

NASA Astrophysics Data System (ADS)

Weeds are typically found in aggregated patches within a production area. Remote sensing technologies have been incorporated into agricultural production systems to locate and manage these troublesome areas site-specifically. Correct weed identification is a key component when making proper weed control decisions. Research was implemented to evaluate the use of hyperspectral and multispectral reflectance data for proper weed and crop discrimination. The primary objectives of this research were to evaluate the utility of hyperspectral radiometry and multispectral imagery to differentiate soybean and six weed species commonly found in Mississippi. Additional objectives included evaluating the spectral characteristics of Palmer amaranth and pitted morningglory accessions collected across central and southern United States. Principal component analysis was ineffective in discriminating between species. Best spectral band combination analysis (BSBC) produced the greatest weed classification accuracies when comparing all classification techniques. The BSBC suggested three areas of interest for species discrimination in the short wavelength infrared portion of the electromagnetic spectrum. These areas of interest were located from 1445 to 1475 nm, 2030 to 2090 nm, and 2115 to 2135 nm. Classification accuracies increased for all species when these band regions were added than when using vegetation indices alone, suggesting greater crop and weed species differentiation can be obtained when using sensors that include these regions of the short wavelength infrared portion of the electromagnetic spectrum. Three supervised classification systems were implemented in multispectral imagery classification. The best classification accuracies of 90% or greater were obtained for many of the plant species at 10 and 12 weeks after emergence using either a 2-class or 3-class system. Palmleaf morningglory and pitted morningglory at the highest densities of 6 plants/m2 produced the highest classification accuracies for the 8-class system once allowed to grow for 10 weeks. Classification accuracies increased as planting density increased. These results demonstrate that multispectral imagery has the potential for weed detection especially when being used in a management system where individual weed species differentiation is not essential, as in the 2-class or 3-class system. Two analysis techniques indicated that the separation among Palmer amaranth and among pitted morningglory accessions is very difficult. Classification accuracies were generally less than 50%, with no observable trends in classification accuracy based upon accession origin. These results suggest there are only slight reflectance characteristic differences between Palmer amaranth and pitted morningglory accessions. These differences may not be predictable based upon accession origin due to the great diversity of Palmer amaranth and pitted morningglory.

Gray, Cody Jack

116

Competition Experiments on Alien Weeds with Crops: Lessons for Measuring Plant Invasion Impact?  

Microsoft Academic Search

Can we quantify the impact of invasive species? Here we use the per-plant competitiveness of alien weeds on crops as a model\\u000a of invasive species impact in general. We reviewed 97 weed–crop competition experiments in 32 papers that included 30 alien\\u000a weed and 14 crop species. The majority (68.92%) were randomised block designs where the alien weed had been either

Montserrat Vilà; Mark Williamson; Mark Lonsdale

2004-01-01

117

Cover crops and interrow tillage for weed control in short season maize ( Zea mays)  

Microsoft Academic Search

Weed competition can cause substantial maize (Zea mays L.) yield reductions. Interseeding maize with cover crops or a combination of interrow cultivation and interseeded cover crops are possible alternative methods of weed control. This study was conducted to examine the potential of interrow cultivation plus cover crops to reduce weed density in maize without reducing the grain yield. Field experiments

O. A. Abdin; X. M. Zhou; D. Cloutier; D. C. Coulman; M. A. Faris; D. L. Smith

2000-01-01

118

Lawn Weed Control with Herbicides. Home and Garden Bulletin No. 123.  

ERIC Educational Resources Information Center

Information and diagrams are given for identification and treatment of weed grasses and broadleaf weeds. Herbicides are suggested for use against each weed and instructions are given for proper application. Information is given for buying herbicides, and applying sprays and cleaning sprayers. (BB)

Agricultural Research Service (USDA), Washington, DC.

119

Software to quantify and map vegetative cover in fallow fields for weed management decisions  

Microsoft Academic Search

Mapping weed cover during the fallow period of dryland crop rotations would be valuable for weed management in subsequent crops and could be done with low cost color digital cameras, however most managers lack the specialized software and expertise needed to create a map from the images. A system of software was developed to quantify weed cover in fallow fields

L. J. Wiles

2011-01-01

120

Weed populations and crop rotations : Exploring dynamics of a structured periodic system  

Microsoft Academic Search

The periodic growing of a certain set of crops in a prescribed order, called a crop rotation, is considered to be an important tool for managing weed populations. Nevertheless, the effects of crop rotations on weed population dynamics are not well understood. Explanations for rotation effects on weed populations usually invoke the diversity of environments caused by different crops that

Shana K. Mertens; Frank van den Bosch

2002-01-01

121

Weed Invasion Susceptibility Prediction (WISP) Model for Use with Geographic Information Systems  

Microsoft Academic Search

The Weed Invasion Susceptibility Prediction (WISP) model was developed as an extension of the ArcView Geographic Information System to predict potential risk of invasion by individual weed species in rangelands. Existence potential was determined by comparing growth requirements of each weed species with respect to nine site characteristics obtained from geographic data layers: distance from water and disturbance sources, elevation,

J. H. Gillham; A. L. Hild; J. H. Johnson; E. R. Hunt; T. D. Whitson

2004-01-01

122

Airborne hyperspectral and LiDAR data integration for weed detection  

NASA Astrophysics Data System (ADS)

Agriculture uses 70% of global available fresh water. However, ca. 50-70% of water used by cultivated plants, the rest of water transpirated by the weeds. Thus, to define the distribution of weeds is very important in precision agriculture and horticulture as well. To survey weeds on larger fields by traditional methods is often time consuming. Remote sensing instruments are useful to detect weeds in larger area. In our investigation a 3D airborne laser scanner (RIEGL LMS-Q680i) was used in agricultural field near Sopron to scouting weeds. Beside the airborne LiDAR, hyperspectral imaging system (AISA DUAL) and air photos helped to investigate weed coverage. The LiDAR survey was carried out at early April, 2012, before sprouting of cultivated plants. Thus, there could be detected emerging of weeds and direction of cultivation. However airborne LiDAR system was ideal to detect weeds, identification of weeds at species level was infeasible. Higher point density LiDAR - Terrestrial laser scanning - systems are appropriate to distinguish weed species. Based on the results, laser scanner is an effective tool to scouting of weeds. Appropriate weed detection and mapping systems could contribute to elaborate water and herbicide saving management technique. This publication was supported by the OTKA project K 105789.

Tamás, János; Lehoczky, Éva; Fehér, János; Fórián, Tünde; Nagy, Attila; Bozsik, Éva; Gálya, Bernadett; Riczu, Péter

2014-05-01

123

Smoking the Other: marijuana and counterhegemony in Weeds.  

PubMed

Subverting suburban modernity, the SHOWTIME television series Weeds invites its audiences to situate their opinions about marijuana amid spheres of bourgeois soccer-moms, class politics, turf wars, raw economics, violent milieux, and multiculti heterogeneity. I argue that Weeds encourages us to "smoke the Other"; that is, to hesitantly accept difference, in line with many drug circles' etiquette. The phrase "smoking the Other" is a critical alteration of bell hooks' (1992, Black looks: Race and representation. Boston: South End Press) conception of whites' ethnic "devouring" as "eating the Other," a rather rigid schematic itself problematized by Weeds' transgressive self-conscious playfulness with stereotyped ethnicities, loopy plotlines, and counterhegemonic dialogue. Cultural/political implications follow. PMID:21599507

Lavoie, Dusty

2011-01-01

124

Phenological observations on shrubs to predict weed emergence in turf.  

PubMed

Phenology is the study of periodic biological events. If we can find easily recognizable events in common plants that precede or coincide with weed emergences, these plants could be used as indicators. Weed seedlings are usually difficult to detect in turf, so the use of phenological indicators may provide an alternative approach to predict the time when a weed appears and consequently guide management decisions. A study was undertaken to determine whether the phenological phases of some plants could serve as reliable indicators of time of weed emergence in turf. The phenology of six shrubs (Crataegus monogyna Jacq., Forsythia viridissima Lindl., Sambucus nigra L., Syringa vulgaris L., Rosa multiflora Thunb., Ziziphus jujuba Miller) and a perennial herbaceous plant [Cynodon dactylon (L.) Pers.] was observed and the emergence dynamics of four annual weed species [Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertner, Setaria glauca (L.) Beauv., Setaria viridis (L.) Beauv.] were studied from 1999 to 2004 in northern Italy. A correlation between certain events and weed emergence was verified. S. vulgaris and F. viridissima appear to be the best indicators: there is a quite close correspondence between the appearance of D. sanguinalis and lilac flowering and between the beginning of emergence of E. indica and the end of lilac flowering; emergences of S. glauca and S. viridis were predicted well in relation to the end of forsythia flowering. Base temperatures and starting dates required to calculate the heat unit sums to reach and complete the flowering phase of the indicators were calculated using two different methods and the resultant cumulative growing degree days were compared. PMID:15846520

Masin, Roberta; Zuin, Maria Clara; Zanin, Giuseppe

2005-09-01

125

Phenological observations on shrubs to predict weed emergence in turf  

NASA Astrophysics Data System (ADS)

Phenology is the study of periodic biological events. If we can find easily recognizable events in common plants that precede or coincide with weed emergences, these plants could be used as indicators. Weed seedlings are usually difficult to detect in turf, so the use of phenological indicators may provide an alternative approach to predict the time when a weed appears and consequently guide management decisions. A study was undertaken to determine whether the phenological phases of some plants could serve as reliable indicators of time of weed emergence in turf. The phenology of six shrubs (Crataegus monogyna Jacq., Forsythia viridissima Lindl., Sambucus nigra L., Syringa vulgaris L., Rosa multiflora Thunb., Ziziphus jujuba Miller) and a perennial herbaceous plant [Cynodon dactylon (L.) Pers.] was observed and the emergence dynamics of four annual weed species [Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertner, Setaria glauca (L.) Beauv., Setaria viridis (L.) Beauv.] were studied from 1999 to 2004 in northern Italy. A correlation between certain events and weed emergence was verified. S. vulgaris and F. viridissima appear to be the best indicators: there is a quite close correspondence between the appearance of D. sanguinalis and lilac flowering and between the beginning of emergence of E. indica and the end of lilac flowering; emergences of S. glauca and S. viridis were predicted well in relation to the end of forsythia flowering. Base temperatures and starting dates required to calculate the heat unit sums to reach and complete the flowering phase of the indicators were calculated using two different methods and the resultant cumulative growing degree days were compared.

Masin, Roberta; Zuin, Maria Clara; Zanin, Giuseppe

2005-09-01

126

Oxadiazon and pendimethalin for control of weeds in groundnut  

Microsoft Academic Search

Field experiments were conducted in groundnut (Arachis hypogaea L.) using three herbicides (oxadiazon, pendimethalin and fluchloralin) applied at different rates and by different methods alongside hand hoed, weedy and weed?free control plots. Pre?planting incorporation of fluchloralin at 1.5 kg a.i.\\/ha and pre?emergence application of oxadiazon at 1.0–2.0 kg a.i.\\/ha, with pendimethalin at 1.0–2.0 kg a.i.\\/ha controlled the major weeds (Echinochloa

V. M. Bhan; S. K. Yadav; S. P. Singh

1983-01-01

127

Study on the weed-crop competition for nutrients in maize.  

PubMed

Considering the effect of crop-weed competition the rate of weed growing, the competitiveness of the occurring weed species and the duration of competition are determining factors. Experiments were carried out on fields in order to collect data on the effect of early weed competition on maize, including the competition for nutrients and the possible rate of nutrient removal by weeds. From 7 sampling areas of the 9.2 ha field weeds and maize samples were collected 1 month after the sowing of maize. We determined the total numbers and the species numbers of weeds by plots. The removed plant species and maize were weighed then dried until the weight balance was reached. The samples were tested for N, P, K and Ca. Comparison was done with the weight and nutrient element content of maize plants taken from the treated, weed-free area. At the same time comparative analyses were made with the mass and nutrient contents of maize plants. There were 12 occurring weed species in this experiment. Based on the rate of weed cover the following species were dominant: Datum stramonium L., Cannabis sativa L., Amaranthus chlorostachis Willd., Chenopodium album L., Chenopodium hybridum L. Our experiments revealed that in the areas being likely to produce high weed populations and showing a considerable high nutrient removal by weeds, the competition between weed plants and maize occurs at an earlier stage of the vegetation period of maize than on fields with moderate weed populations. Weeds have utilised significant amount of nutrients which has been many fold of maize in case of unit area. PMID:15149132

Lehoczky, E; Reisinger, P

2003-01-01

128

Herbicide-Resistant Crops: Utilities and Limitations for Herbicide-Resistant Weed Management  

PubMed Central

Since 1996, genetically modified herbicide-resistant (HR) crops, particularly glyphosate-resistant (GR) crops, have transformed the tactics that corn, soybean, and cotton growers use to manage weeds. The use of GR crops continues to grow, but weeds are adapting to the common practice of using only glyphosate to control weeds. Growers using only a single mode of action to manage weeds need to change to a more diverse array of herbicidal, mechanical, and cultural practices to maintain the effectiveness of glyphosate. Unfortunately, the introduction of GR crops and the high initial efficacy of glyphosate often lead to a decline in the use of other herbicide options and less investment by industry to discover new herbicide active ingredients. With some exceptions, most growers can still manage their weed problems with currently available selective and HR crop-enabled herbicides. However, current crop management systems are in jeopardy given the pace at which weed populations are evolving glyphosate resistance. New HR crop technologies will expand the utility of currently available herbicides and enable new interim solutions for growers to manage HR weeds, but will not replace the long-term need to diversify weed management tactics and discover herbicides with new modes of action. This paper reviews the strengths and weaknesses of anticipated weed management options and the best management practices that growers need to implement in HR crops to maximize the long-term benefits of current technologies and reduce weed shifts to difficult-to-control and HR weeds.

2010-01-01

129

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

PubMed

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. PMID:24430973

Adkins, Steve; Shabbir, Asad

2014-07-01

130

[Potential role of winter rape weeds in the extension of broomrape in Poitou-Charentes].  

PubMed

In the Poitou-Charentes district, among the 82 species of winter rape weeds identified, 22 displayed a strong affinity for this crop (Brassica napus L.). In fields, 50% of these weeds were parasitized by Orobanche ramosa, playing the role of host plants. Greenhouse co-cultures (weed/Orobanche ramosa) showed that weeds non-parasitized in fields could be attacked by broomrape, developing a more or less complete cycle. In vitro co-cultures (weed/Orobanche ramosa) revealed that root exudates of non-parasitized weeds, in fields or in greenhouse co-cultures, could induce Orobanche ramosa seed germination, but not attachment. These weeds could play the role of false hosts. PMID:14556384

Gibot-Leclerc, Stéphanie; Brault, Marianne; Pinochet, Xavier; Sallé, Georges

2003-07-01

131

Real-time weed detection in outdoor field conditions  

NASA Astrophysics Data System (ADS)

Though most herbicide is applied uniformly in agronomic fields, there is strong evidence that weeds are not distributed uniformly within the crop fields. If an effective weed detection system were developed, both economic and environmental benefits would result from its use for site-specific weed management. Past work in this area has focused mainly on either low spatial resolution photo-detectors or off-line machine vision system. This study was undertaken to develop real-time machine vision weed detection for outdoor lighting conditions. The novel environmentally adaptive segmentation algorithm was developed with the objective of real-time operation on an on-board computer-based system. The EASA used cluster analysis to group pixels of homogeneous color regions of the image together which formed the basis for image segmentation. The performance of several variations of this algorithm was measured by comparing segmented field images produced by the EASA, fixed-color HSI region segmentation, and ISODATA clustering with hand-=segmented reference images. The time cost and questionable accuracy of hand- segmented reference images led to exploration of the use of computer-segmented reference images. Sensitivity and background sensitivity were used as performance measured. Significant differences were found between the means of sensitivity, background sensitivity, and overall performance across segmentation schemes. Similar results were obtained with computer-segmented reference images.

Steward, Brian L.; Tian, Lei F.

1999-01-01

132

Developing weed-suppressive soils through improved soil quality management  

Microsoft Academic Search

Manipulating soil microbial communities using soil and crop management practices is a basic strategy in developing sustainable agricultural systems. Sustainable farming is based, in part, on the efficient management of soil microorganisms to improve soil quality. However, the identification of biological indicators of soil quality that can be used to predict weed suppression in soils has received little attention. We

Robert J Kremer; Jianmei Li

2003-01-01

133

Weed Control Management Plan for Wildflower Plant Beds.  

National Technical Information Service (NTIS)

A large number of herbicides were evaluated in this research that have potential use with wildflowers. The manager can use this research as a basis to begin development of a weed management plan that will minimize wildflower injury and maximize reseeding ...

W. A. Skroch L. Gallitano G. Mahnken C. Catanzaro

1995-01-01

134

Solanum viarum: Weed reservoir of plant viruses in Florida  

Microsoft Academic Search

Solanum viarum Dunal (tropical soda apple), an introduced and rapidly spreading weed, currently infests over 60 000 ha in Florida. Approximately 220 plants were sampled in seven stands of S. viarum in south?west and west central Florida during 1992 and 1993 to determine the occurrence of nine viruses which can infect solanaceous crops. Virus detection utilized a double antibody sandwich?enzyme

R. J. McGovern; J. E. Polston; J. J. Mullahey

1994-01-01

135

Weed Killer Deforms Sex Organs in Frogs, Study Finds  

NSDL National Science Digital Library

This Web site discusses current research findings surrounding the use of the weed killer, atrazine, and sex organ deformities in frogs exposed to it. The article from the New York Times summarizes the recent research report; free registration is required to view it. This site reports focus on the potential impact of atrazine on humans, but they do raise it as an important question.

Press., Associated

2002-01-01

136

Laser-induced fluorescence for discrimination of crops and weeds  

NASA Astrophysics Data System (ADS)

This paper reports the use of Laser Induced Fluorescence (LIF) of plants to discriminate between crops and weeds for potential use in an intelligent crop spraying system. Past and current work in intelligent crop spraying has concentrated on using multi-spectral reflectance data in particular using near infrared (NIR) and color. Texture and shape image processing has also been used with limited success and is usually computationally expensive. Also, most of these approaches are error prone since they rely on ambient solar illumination and so are susceptible to errors caused by cloud variations, shadows and other non-uniformities. There are several commercial spraying systems available that detect presence or absence of plants using the NIR 'red-edge' effect without discrimination between species. 'Weedseeker' and 'Detectspray' are two examples of such systems, the 'Weedseeker' system being one of the few active systems, incorporating its own light source. However, both systems suffer from poor spatial resolution. The use of plant or chlorophyll fluorescence for discrimination between species is a relatively under researched area. This paper shows that LIF of several crops and weeds can be used to discriminate between species. Spectra are presented for two crop and two weed species over a range of discrete laser excitation wavelengths. The technique can be directly implemented with a laser imaging system for real-time detection and discrimination of crops and weeds.

Hilton, Peter J.

2000-11-01

137

Herbicide Leaching Column for a Weed Science Teaching Laboratory.  

ERIC Educational Resources Information Center

Presents an experiment which enables weed science students to observe first-hand the process of herbicide leaching in soils. Features of this technique which demonstrate the movement of herbicide within a column of soil are outlined. Diagrams are provided of the apparatus employed in the exercise. (ML)

Ahrens, W. H.

1986-01-01

138

Biomass Based Weed-Crop Competitiveness Classification Using Bayesian Networks  

Microsoft Academic Search

This paper describes the modeling of a biomass based weed-crop competitiveness classification process, based on a Bayesian network classifier. The understandability of the model is improved by its automatic translation into a set of classification rules, which are easily understood by human beings. The Bayes approach is based on empirical data collected in a corn-crop and uses the concept of

Glaucia M. Bressan; Vilma A. Oliveira; Estevam R. Hruschka Jr; Maria C. Nicoletti

2007-01-01

139

Thermal Band Heating for Intra-Row Weed Control  

Microsoft Academic Search

For many years, disinfection of the soil by means of steaming has been a common method for eliminating weeds and fungal diseases. However, surface steaming of soil is a very energy-intensive process, and consequently, efforts have been made to develop a machine for narrow-band steaming of the soil under and around rows of cultivated plants prior to seeding. The use

M. H. Jørgensen; E. F. Kristensen; J. K. Kristensen; B. Melander

140

Integrated dryland weed control in nature farming systems  

Microsoft Academic Search

As practices of integrated weed control in nature farming systems, surface application of a bioactive organic fertilizer, pigtailed wheat straw mulch, and intercropped peanut as a smother crop were tested with soybean, Japanese pumpkin and tomato, respectively. A bioactive organic fertilizer using rice bran, oil mill sludge and fish meal as materials and a microbial inoculant (EM as its commercial

Hui-lian Xu; Feifei Qin; Fahong Wang; Qicong Xu; Shailendra K. Shah; Fengmin Li

2009-01-01

141

Selecting for Weed Resistance: Herbicide Rotation and Mixture  

Microsoft Academic Search

Herbicide rotations and mixtures are widely recommended to manage herbicide resistance. However, little research has quantified how these practices actually affect the selection of herbicide resistance in weeds. A 4-yr experiment was conducted in western Canada from 2004 to 2007 to examine the impact of herbicide rotation and mixture in selecting for acetolactate synthase (ALS) inhibitor resistance in the annual

Hugh J. Beckie; Xavier Reboud

2009-01-01

142

ECOLOGICAL IMPACT OF INTEGRATED CHEMICAL AND BIOLOGICAL AQUATIC WEED CONTROL  

EPA Science Inventory

This final report presents results of a four-year study of the ecological impacts of chemical, biological, and integrated methods of aquatic weed control. Biological and water quality changes occurred as abundance of macrophytic vegetation was altered by natural factors or manage...

143

Confused about Fusion? Weed Your Science Collection with a Pro.  

ERIC Educational Resources Information Center

Provides guidelines on weeding science collections in junior high/high school libraries. Highlights include checking copyright dates, online sources, 13 science subject areas that deserve special consideration (plate tectonics, fission, fusion, radioactive dating, weather/climate, astronomy/space science, elements, integrated science,…

O'Dell, Charli

1998-01-01

144

Weed control in rice with metham-sodium.  

PubMed

Metam-sodium is a soil fumigant with herbicidal properties. A field experiment was conducted in 2000 at Copiano (Pavia, Italy) to determine the efficacy of three rates of metam-sodium (300, 450 and 600 l/ha) at three different planting times (5, 12 and 18 days after chemical treatments) for the control of weeds in rice cultivation. The study mainly focused on the control of red rice (Oryza sativa var. selvatica), a weed which is worldwide distributed in rice fields and difficult to eradicate Test design was a split-plot with four replications. The main plot size was 13, 5 by 15 m and the subplot size was 13, 5 by 5 m. The chemical treatments were carried out as pre-sowing. Two days after chemical treatments, all field plots were flooded with 10 cm of water as practiced locally. An early variety of rice (Loto) was sown at 150 kg/ha. Weed control was visually evaluated as a percentage of ground covering by all weeds and by each weed individually at three, four and five weeks after treatments. Observations were made also on rice selectivity, and rice grain yield was assessed at the end. Metam-sodium did not injure the rice plants. Metam-sodium at 450 l/ha controlled 100%, 97% and 92% of red rice at the first, second and third observations, respectively. Good results were also obtained with metam-sodium at 300 and 600 l/ha, which controlled 94 to 82% of red rice during the season. Echinochloa crus-galli was better controlled with the higher rates of metam-sodium, particularly in the early part of the season. Metam-sodium did not show enough efficacy in this study against Heteranthera reniformis, Bulboschoenus maritimus and Lindernia spp. The best rice grain yield was obtained with all rates of metam-sodium, when rice was sown 5 days after treatment. PMID:17390826

Sparacino, A C; Ferro, R; Riva, N; Ditto, D; Tano, F; Croce, G; Rabasse, J M

2006-01-01

145

Circadian response of annual weeds to glyphosate and glufosinate.  

PubMed

Five field experiments were conducted in 1998 and 1999 in Minnesota to examine the influence of time of day efficacy of glyphosate [N-(phosphonomethyl)glycine] and glufosinate [2-amino-4-(hydroxymethyl-phosphinyl)butanoic acid] applications on the control of annual weeds. Each experiment was designed to be a randomized complete block with four replications using plot sizes of 3 x 9 m. Glyphosate and glufosinate were applied at rates of 0.421 kg ae/ha and 0.292 kg ai/ha, respectively, with and without an additional adjuvant that consisted of 20% nonionic surfactant and 80% ammonium sulfate. All treatments were applied with water at 94 L/ha. Times of day for the application of herbicide were 06:00h, 09:00h, 12:00h, 15:00h, 18:00h, 21:00h, and 24:00h. Efficacy was evaluated 14 d after application by visual ratings. At 14 d, a circadian response to each herbicide was found, with greatest annual weed control observed with an application occurring between 09:00h and 18:00h and significantly less weed control observed with an application at 06:00h, 21:00h, or 24:00h. The addition of an adjuvant to both herbicides increased overall efficacy, but did not overcome the rhythmic time of day effect. Results of the multiple regression analysis showed that after environmental temperature, time of day was the second most important predictor of percent weed kill. Thus, circadian timing of herbicide application significantly influenced weed control with both glyphosate and glufosinate. PMID:12025933

Martinson, Krishona B; Sothern, Robert B; Koukkari, Willard L; Durgan, Beverly R; Gunsolus, Jeffrey L

2002-03-01

146

Cultivar weed-competitiveness in aerobic rice : heritability, correlated traits, and the potential for indirect selection in weed-free environments  

Microsoft Academic Search

Forty rice (Oryza sativa L.) cultivars and breeding lines used in the International Rice Research Institute (IRRI) upland rice breeding program were evaluated in adjacent weed-free and weedy trials in aerobic soil conditions during the wet seasons of 2001, 2002, and 2003. The objectives of this study were to investigate genetic variability in weed suppression and yield and to identify

D. L. Zhao; G. N. Atlin; L. Bastiaans; J. H. J. Spiertz

2006-01-01

147

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

PubMed

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. PMID:24519007

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

2014-03-01

148

Allergens of weed pollen: an overview on recombinant and natural molecules.  

PubMed

Weeds represent a botanically unrelated group of plants that usually lack commercial or aesthetical value. Pollen of allergenic weeds are able to trigger type I reactions in allergic patients and can be found in the plant families of Asteraceae, Amaranthaceae, Plantaginaceae, Urticaceae, and Euphorbiaceae. To date, 34 weed pollen allergens are listed in the IUIS allergen nomenclature database, which were physicochemically and immunologically characterized to varying degrees. Relevant allergens of weeds belong to the pectate lyase family, defensin-like family, Ole e 1-like family, non-specific lipid transfer protein 1 family and the pan-allergens profilin and polcalcins. This review provides an overview on weed pollen allergens primarily focusing on the molecular level. In particular, the characteristics and properties of purified recombinant allergens and hypoallergenic derivatives are described and their potential use in diagnosis and therapy of weed pollen allergy is discussed. PMID:23806644

Gadermaier, Gabriele; Hauser, Michael; Ferreira, Fatima

2014-03-01

149

Identification of Begomoviruses Infecting Crops and Weeds in Belize  

PubMed Central

Plants including pepper, red kidney bean, squash, string bean and tomato, as well as weeds with viral symptoms were collected from five districts in Belize over a three year period with the aim of determining the diversity of the begomoviruses present. Sixty five percent of the samples screened via DNA hybridization produced signals indicative of begomovirus infection. Subsequent PCR amplifications and nucleotide sequence analyses revealed the presence of four begomoviruses in Belize. Pepper golden mosaic virus and Tomato mottle virus-[Flo] were found associated with tomato and sweet pepper and the former was also isolated from hot pepper. Merremia mosaic virus was found infecting hot pepper, sweet pepper and the weed species Euphorbia heterophylla. Euphorbia mosaic virus-[Yucatan Peninsula] was found in hot pepper and Euphorbia. This is the first report of the identification of begomoviruses in Belize.

McLaughlin, Pamela D.; McLaughlin, Wayne A.; Maxwell, Douglas P.; Roye, Marcia E.

2010-01-01

150

Identification of Begomoviruses Infecting Crops and Weeds in Belize.  

PubMed

Plants including pepper, red kidney bean, squash, string bean and tomato, as well as weeds with viral symptoms were collected from five districts in Belize over a three year period with the aim of determining the diversity of the begomoviruses present. Sixty five percent of the samples screened via DNA hybridization produced signals indicative of begomovirus infection. Subsequent PCR amplifications and nucleotide sequence analyses revealed the presence of four begomoviruses in Belize. Pepper golden mosaic virus and Tomato mottle virus-[Flo] were found associated with tomato and sweet pepper and the former was also isolated from hot pepper. Merremia mosaic virus was found infecting hot pepper, sweet pepper and the weed species Euphorbia heterophylla. Euphorbia mosaic virus-[Yucatan Peninsula] was found in hot pepper and Euphorbia. This is the first report of the identification of begomoviruses in Belize. PMID:20596296

McLaughlin, Pamela D; McLaughlin, Wayne A; Maxwell, Douglas P; Roye, Marcia E

2008-01-01

151

A Hybrid Differential Invasive Weed Algorithm for Congestion Management  

NASA Astrophysics Data System (ADS)

This work is dedicated to solve the problem of congestion management in restructured power systems. Nowadays we have open access market which pushes the power system operation to their limits for maximum economic benefits but at the same time making the system more susceptible to congestion. In this regard congestion management is absolutely vital. In this paper we try to remove congestion by generation rescheduling where the cost involved in the rescheduling process is minimized. The proposed algorithm is a hybrid of Invasive Weed Optimization (IWO) and Differential Evolution (DE). The resultant hybrid algorithm was applied on standard IEEE 30 bus system and observed to beat existing algorithms like Simple Bacterial foraging (SBF), Genetic Algorithm (GA), Invasive Weed Optimization (IWO), Differential Evolution (DE) and hybrid algorithms like Hybrid Bacterial Foraging and Differential Evolution (HBFDE) and Adaptive Bacterial Foraging with Nelder Mead (ABFNM).

Basak, Aniruddha; Pal, Siddharth; Pandi, V. Ravikumar; Panigrahi, B. K.; Das, Swagatam

152

Deciphering the evolution of herbicide resistance in weeds.  

PubMed

Resistance to herbicides in arable weeds is increasing rapidly worldwide and threatening global food security. Resistance has now been reported to all major herbicide modes of action despite the development of resistance management strategies in the 1990s. We review here recent advances in understanding the genetic bases and evolutionary drivers of herbicide resistance that highlight the complex nature of selection for this adaptive trait. Whereas early studied cases of resistance were highly herbicide-specific and largely under monogenic control, cases of greatest concern today generally involve resistance to multiple modes of action, are under polygenic control, and are derived from pre-existing stress response pathways. Although 'omics' approaches should enable unraveling the genetic bases of complex resistances, the appearance, selection, and spread of herbicide resistance in weed populations can only be fully elucidated by focusing on evolutionary dynamics and implementing integrative modeling efforts. PMID:23830583

Délye, Christophe; Jasieniuk, Marie; Le Corre, Valérie

2013-11-01

153

Effects of alternative winter cover cropping systems on weed suppression in organically grown tomato ( Solanum lycopersicum )  

Microsoft Academic Search

Weed control is a major concern for organic farmers around the world and non-chemical weed control methods are now the subject\\u000a of many investigations. Field studies were conducted in tomato (Solanum lycopersicum L.) from 2004 to 2006 at the Black Sea Agricultural Research Institute experiment field to determine the weed suppressive\\u000a effects of winter cover crops. Treatments consisted of ryegrass

Husrev Mennan; Mathieu Ngouajio; Dogan Is?k; Emine Kaya

2009-01-01

154

Single herbicide treatments for control of broadleaved weeds in onion ( Allium cepa)  

Microsoft Academic Search

Experiments were conducted for two consecutive seasons to evaluate the efficacy of herbicides for control of broadleaved weeds which were applied only once in irrigated onion. Oxyfluorfen and oxadiazon were used both pre- and post-emergence, metribuzin only pre-emergence, and bentazon only post-emergence. Hand-weeded and weedy checks were included. Visual ratings estimated 65 days after crop emergence indicated that weed control

H. Z. Ghosheh

2004-01-01

155

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

PubMed Central

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.

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

156

WEED COMMUNITIES OF SUNFLOWER CROP IN SUKKUR AND KHAIRPUR, SINDH: AUTUMN ASPECT  

Microsoft Academic Search

The survey of weed communities of sunflower crop was conducted in five sunflower growing areas of Sukkur and Khairpur districts during 2003. A total of 33 weed species belonging to 30 genera and 15 angiosperm families were recorded. Five weed communities viz.: 1) Cyperus-Eclipta-Brachiaria in Ghulam Qasim Jiskani (district Khairpur), 2) Dactyloctenium-Cyperus- Brachiaria in Kotedji (district Khairpur), 3) Trianthema- Cyperus-Brachiaria

Rahmatullah Qureshi; Rabia Asma Memon

157

Weed control and yield response of soil solarization with different plastic films in lettuce  

Microsoft Academic Search

Phase out of most chemicals available for weed management renewed the interest in soil solarization as a technically effective and environmentally safe practice for lettuce weed control in hot summer areas. Properties of solarizing films and lettuce crop system may considerably affect weed control and yield response of soil solarization. Different solarizing films, including low-density polyethylene, ethylene-vinyl acetate copolymer, low-density

Vincenzo Candido; Trifone D’Addabbo; Vito Miccolis; Donato Castronuovo

2011-01-01

158

Weed control in cauliflower ( Brassica oleracea var. Botrytis L.) with herbicides  

Microsoft Academic Search

Field experiments were carried out to evaluate the effect of different herbicides on weeds and cauliflower (Brassica oleracea var. Botrytis cv. White Cloud) grown under Jordan Valley conditions during the 1996\\/1997 and 1997\\/1998 growing seasons. The most common weed species were Chenopodium murale L. (133plantsm?2), Malva sylvestris L. (38plantsm?2) and Echinochloa colonum (L.) Link (13plantsm?2). On average, weed competition for

J. R. Qasem

2007-01-01

159

Water Hyacinths and Alligator Weeds for Final Filtration of Sewage  

NASA Technical Reports Server (NTRS)

The potential of water hyacinths (Eichhornia crassipes) (Mart.) Solms and alligator weeds (Alternanthera philoxerides) (Mart.) Griesb. as secondary and tertiary filtration systems for domestic sewage was demonstrated. These two vascular aquatic plants reduced the suspended solids, total Kjeldahl nitrogen, total phosphorus, BOD sub 5, and total organic carbon levels in domestic sewage from 60 percent to 98 percent within a two week period. These plants grown in domestic sewage were also free of toxic levels of trace heavy metals.

Wolverton, B. C.; Mcdonald, R. C.; Gordon, J.

1976-01-01

160

WEED SCIENCE Wild Okra Control with Bromoxynil and Pyrithiobac  

Microsoft Academic Search

Wild okra (Abelmoschus esculentus (L.) Moench), a summer annual, is a potentially serious weed in cotton (Gosssypium hirsutum L.) fields of the southeastern United States. This study was conducted in 1995 and 1996 to evaluate wild okra control by bromoxynil (3,5-dibromo-4- hydroxybenzonitrile) and pyrithiobac {2-chloro-6-((4,6-dimethoxy-2- py r i m idin y l)thio)benzoic a c i d } a pp l

Eric P. Prostko; Enrique Rosales-Robles; James M. Chandler

1998-01-01

161

Chemical weed control in Bulgarian coriander (Coriandrum sativum L.)  

Microsoft Academic Search

Field investigations carried out in two winter seasons of 1984–85 and 1985–86 on clay?loam soil at the Central Institute of Medicinal and Aromatic Plants, Regional Centre, Pantnagar, Naintial, India revealed that unrestricted weed growth reduced the seed and oil yields of Bulgarian coriander (Coriandrum sativum L. cv. S 33) by 40.3 and 37.0%, respectively. Applications of pendimethalin and fluchloralin at

S. K. Kothari; J. P. Singh; Kamla Singh

1989-01-01

162

Chemical weed control in irrigated sweet pepper (Capsicum annuum L.)  

Microsoft Academic Search

Field trials were conducted at Kadawa in the 1983\\/4 and 1984\\/5 dry seasons to evaluate some herbicide treatments for weed control in transplanted irrigated sweet pepper (Capsicum annuum L., var. California mild). In the 1983\\/4 dry season, mixtures of metolachlor with metribuzin at 1.5 + 0.25 and pendimethalin plus linuron at 1.5 + 0.75 kg a.i.\\/ha, each followed by supplementary

J. A. Adigun; S. T. O. Lagoke; S. K. Karikari

1991-01-01

163

Allelopathy in crop/weed interactions--an update.  

PubMed

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. PMID:17195966

Belz, Regina G

2007-04-01

164

Killing Weeds with 2,4-D. Extension Bulletin 389.  

ERIC Educational Resources Information Center

Discussed is the use of the herbicide 2,4-D. Though written for farmers and agricultural workers, the pamphlet considers turf weed control and use of 2,4-D near ornamental plants. Aspects of the use of this herbicide covered are: (1) the common forms of 2,4-D; (2) plant responses and tolerances to the herbicide; (3) dilution and concentration of…

Lee, Oliver C.

165

Potential for phytoextraction of PCBs from contaminated soils using weeds  

Microsoft Academic Search

A comprehensive investigation of the potential of twenty-seven different species of weeds to phytoextract polychlorinated biphenyls (PCBs) from contaminated soil was conducted at two field sites (Etobicoke and Lindsay) in southern Ontario, Canada. Soil concentrations were 31?g\\/g and 4.7?g\\/g at each site respectively. All species accumulated PCBs in their root and shoot tissues. Mean shoot concentrations at the two sites

Sarah A. Ficko; Allison Rutter; Barbara A. Zeeb

2010-01-01

166

National Evaluation of Weed & Seed: Cross-Site Analysis  

NSDL National Science Digital Library

Published this month by the Department of Justice, this report assesses the results of the "weed and seed" approach to crime prevention, monitored for the last eight years at eight selected area sites in the U.S.. "Weeding" is defined as "concentrated and enhanced law enforcement efforts to identify, arrest, and prosecute" criminals, especially violent offenders and drug traffickers. The cited objective is the removal of criminals from the targeted area. "Seeding" involves community efforts to deter further crime by offering a variety of human services, including afterschool, weekend, and summer youth activities; adult literacy classes; parental counseling; and neighborhood revitalization. The report offers cross-site analysis and finds that the most effective results were achieved in sites of smaller geographical area with more community resources to bring to bear. The report concludes that "in selecting sites for new program funding, Weed and Seed should place its funding priority on sites with geographically small target areas and with favorable community settings and program designs."

Cordner, Gary.; Dunworth, Terence.; Green, Jack.; Mills, Gregory.

167

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

NASA Astrophysics Data System (ADS)

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.

Gumz, Mary Saumur Paulson

168

How weeds emerge: a taxonomic and trait-based examination using United States data.  

PubMed

Weeds can cause great economic and ecological harm to ecosystems. Despite their importance, comparisons of the taxonomy and traits of successful weeds often focus on a few specific comparisons - for example, introduced versus native weeds. We used publicly available inventories of US plant species to make comprehensive comparisons of the factors that underlie weediness. We quantitatively examined taxonomy to determine if certain genera are overrepresented by introduced, weedy or herbicide-resistant species, and we compared phenotypic traits of weeds to those of nonweeds, whether introduced or native. We uncovered genera that have more weeds and introduced species than expected by chance and plant families that have more herbicide-resistant species than expected by chance. Certain traits, generally related to fast reproduction, were more likely to be associated with weedy plants regardless of species' origins. We also found stress tolerance traits associated with either native or introduced weeds compared with native or introduced nonweeds. Weeds and introduced species have significantly smaller genomes than nonweeds and native species. These results support trends for weedy plants reported from other floras, suggest that native and introduced weeds have different stress adaptations, and provide a comprehensive survey of trends across weeds within the USA. PMID:24494694

Kuester, Adam; Conner, Jeffrey K; Culley, Theresa; Baucom, Regina S

2014-05-01

169

Airborne gamma-ray spectrometer and magnetometer survey: Weed quadrangle, California. Final report  

SciTech Connect

Volume II contains the flight path, radiometric multi-parameter stacked profiles, magnetic and ancillary parameter stacked profiles, histograms, and anomaly maps for the Weed Quadrangle in California.

Not Available

1981-05-01

170

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

NASA Astrophysics Data System (ADS)

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.

Hahn, Federico

1995-04-01

171

Changes in Sensitization Rate to Weed Allergens in Children with Increased Weeds Pollen Counts in Seoul Metropolitan Area  

PubMed Central

The prevalence of allergic diseases in children has increased for several decades. We evaluated the correlation between pollen count of weeds and their sensitization rate in Seoul, 1997-2009. Airborne particles carrying allergens were collected daily from 3 stations around Seoul. Skin prick tests to pollen were performed on children with allergic diseases. Ragweed pollen gradually increased between 1999 and 2005, decreased after 2005 and plateaued until 2009 (peak counts, 67 in 2003, 145 in 2005 and 83 grains/m3/day in 2007). Japanese hop pollen increased between 2002 and 2009 (peak counts, 212 in 2006 and 492 grains/m3/day in 2009). Sensitization rates to weed pollen, especially ragweed and Japanese hop in children with allergic diseases, increased annually (ragweed, 2.2% in 2000 and 2.8% in 2002; Japanese hop, 1.4% in 2000 and 1.9% in 2002). The age for sensitization to pollen gradually became younger since 2000 (4 to 6 yr of age, 3.5% in 1997 and 6.2% in 2009; 7 to 9 yr of age, 4.2% in 1997 and 6.4% in 2009). In conclusion, sensitization rates for weed pollens increase in Korean children given increasing pollen counts of ragweed and Japanese hop.

Kim, Joo-Hwa; Lee, Ha-Baik; Kim, Seong-Won; Kang, Im-Joo; Kook, Myung-Hee; Kim, Bong-Seong; Park, Kang-Seo; Baek, Hey-Sung; Kim, Kyu-Rang; Choi, Young-Jean

2012-01-01

172

Early growth of Quercus castaneifolia (C.A. Meyer) seedlings as affected by weeding, shading and irrigation.  

PubMed

The influence of shading, irrigation and weeding on survival, growth and morphology of 1-year Quercus castaneifolia seedlings was studied in north of Iran. The seedlings were grown under eight treatments including full-light versus artificial shading, irrigation versus non-irrigation and weed presence versus weed removing at three replicates. At the end of the first growing season seedling survival in all treatments was 100%. Weed removing had positive effect on height, diameter growth, slenderness coefficient and leaf area of Q. castaneifolia. Irrigation enhanced diameter growth and leaf area and shading increased leaf area. Irrigation had no significant effect on plant growth where the weed was removed. In weed plots seedlings growth and leaf area were greater in shading than in full-light. The results indicated that for 1 year Q. castaneifolia seedlings, weeding, in contrast to irrigation, is an essential factor. Where the weed competition is a difficulty, plantation with higher stem length should be applied. PMID:19070109

Mirzaei, Javad; Tabari, Masoud; Daroodi, Hadi

2007-08-01

173

Incidence of sugarcane shoot borer under different levels of weed competition, crop geometry, intercropping and nutrient supply systems  

Microsoft Academic Search

The effect of selected agronomic practices on the incidence of sugarcane shoot borerChilo infuscatellus Snellen (Lepidoptera: Crambidae) was examined. In an experiment on critical periods of crop-weed competition, wherein sugarcane\\u000a crop was maintained with different weed regimes, the incidence of borer was significantly lower in weedy crop than in weed-free\\u000a crop. The study suggested that crop-weed vegetational diversity maintained up

J. Srikanth; K. P. Salin; S. Easwaramoorthy; C. Kailasam

2002-01-01

174

Environmental Risk Assessment of Compost Prepared from Salvinia, Egeria densa, and Alligator Weed  

Microsoft Academic Search

Approximately 70,000 m 3 of salvinia (Salvinia molesta) was removed from the Hawkesbury-Nepean River, New South Wales (NSW), Australia, during 2004. Th is study assessed the risks associated with applying compost prepared from aquatic weeds (AWC) to land, namely, survival and spread of aquatic and terrestrial weeds, eutrophication of waterways, accumulation of heavy metals and phytotoxicity. Th e results demonstrate

C. G. Dorahy; A. D. Pirie; I. McMaster; L. Muirhead; P. Pengelly; K. Y. Chan; I. M. Barchia

175

Briquetting soda weed ( Salsola tragus) to be used as a rural fuel source  

Microsoft Academic Search

Amount of traditional fuel sources in the world has been decreasing and there is a definite need to produce and utilize alternative fuels such as biomass materials. In this study, briquetting conditions of Russian tumbleweed, Salsola tragus, (commonly named soda weed in Turkey) which grows in salty soils were investigated.Soda weeds were first chopped coarsely in a local tresher, then

Hasan Yumak; Tamer Ucar; Nesim Seyidbekiroglu

2010-01-01

176

Arable weeds as indicators of agricultural intensity – A case study from Finland  

Microsoft Academic Search

The study aimed at developing an agro-biodiversity indicator based on trophic interactions between 25 common arable weeds and individual groups of farmland birds, pollinators (wild bees), phytophagous insects and insect pests. Each weed species was weighted based on the number of reported linkages with each animal group. Four biodiversity indices based on these weights were constructed and applied to exploring

Terho Hyvönen; Erja Huusela-Veistola

2008-01-01

177

Growth Suppression of Annual Weeds by Deleterious Rhizobacteria Integrated with Cover Crops  

Microsoft Academic Search

Development and rapid acceptance of biological control is challenged by factors lim- iting the spectrum of activity, efficacy, and reliability. Effectiveness of biological control may be best demonstrated as a component in an overall biological weed management sys- tem. Cover crops as components of biological weed management may be used for inte- grating biological control agents by promoting establishment in

R. J. KREMER

178

Dalmatian Toadflax, an Invasive Exotic Noxious Weed, Threatens Flagstaff Pennyroyal Community Following Prescribed Fire  

Microsoft Academic Search

Many noxious weed infestations are initiated or increased by soil disturbance. With the recent emphasis on reintroduction of fire into natural ecosystems there has been increased interest in the effects of noxious weeds following fires. This paper discusses the effects of fire on Flagstaff pennyroyal, a Forest Service Region 3 sensitive plant, and the subsequent infesta- tion of the project

BARBARA GOODRICH PHILLIPS; DEBRA CRISP

179

The taxonomic distribution of invasive angiosperm plants: Ecological insights and comparison to agricultural weeds  

Microsoft Academic Search

Global data sets of serious agricultural weeds (1348 species), widespread agricultural weeds (1041 species), and threatening natural area invaders (381 species) were assembled, and taxonomic patterns among these data sets were compared to gain insights into how these groups differ ecologically. Angiosperm taxonomic groups (families, orders and subclasses) were tested for over- and under-representation using resampling tests, and ecological characteristics

Curtis C. Daehler

1998-01-01

180

Symposium Long-term weed management studies in the Pacific Northwest  

Microsoft Academic Search

The winter wheat production system of the Pacific Northwest is characterized by severe wind and water erosion and winter annual grass weeds requiring high herbicide input. Since 1985, numerous multi- and interdisciplinary, long-term, large-scale, integrated cropping systems studies have been or are currently being conducted. The primary focus of these studies was on weed biology, ecology, and management, whereas secondary

Frank L. Young

2004-01-01

181

Evolution of herbicide resistance in weeds: vertically transmitted fungal endophytes as genetic entities  

Microsoft Academic Search

The appearance of heritable resistance to herbicides in weeds is an evolutionary process driven by human selection. Assuming that spontaneous and random mutations originate herbicide resistance genes, which are selected by selection pressure imposed by herbicides, is the simplest model to understand how this phenomenon appears and increases in weed populations. However, the rate of herbicide resistance evolution is not

Martin M. Vila-Aiub; M. Alejandra Martinez-Ghersa; Claudio M. Ghersa

2003-01-01

182

Uncropped edges of arable fields managed for biodiversity do not increase weed occurrence in adjacent crops  

Microsoft Academic Search

Ten experimental management regimes, designed to quantify benefits to weed control and wildlife conservation on uncropped field edges of expanded width, were examined for effects on the weed flora within adjacent arable crops. The treatments involved cutting, sowing and herbicide regimes, with differing effects on plant and invertebrate populations. The relative abundance of all plant species within the adjacent crop

H. Smith; L. G. Firbank; D. W. Macdonald

1999-01-01

183

Linkages among agronomic, environmental and weed management characteristics in North American sweet corn  

Microsoft Academic Search

Much of our understanding of weed communities and their interactions with crops comes from studies conducted at, or below, the spatial scale of individual fields. This scale allows for tight control of experimental variables, but systematically ignores the potential for regional-scale environmental variation to affect agronomic operations and thereby influence weed management outcomes. We quantified linkages among agronomic, environmental and

Martin M. Williams II; Adam S. Davis; Tom L. Rabaey; Chris M. Boerboom

2009-01-01

184

Evaluation of different herbicides for protection of gladiolus ( Gladiolus spp.) crop from weeds  

Microsoft Academic Search

A field experiment to study the effects of various pre- and post-emergence herbicides on weed infestation and on corm and cormel production in three gladiolus (Gladiolus spp.) cultivars was carried out during 1997–2000 at IHBT, Palampur. The main weeds infesting the experimental farm were Ageratum conyzoides, Gnaphalium peregrinum, Plantago lanceolata, Cynodon dactylon, Amaranthus viridis, Paspalum dilatatum, Portulaca oleracea, Euphorbia hirta,

S. Manuja; Raja Ram; R. D. Singh; D. Mukherjee

2005-01-01

185

Real World of Industrial Chemistry: The Challenge of Herbicides for Aquatic Weeds.  

ERIC Educational Resources Information Center

Discusses problems in selecting the correct herbicide for use in controlling aquatic weeds, considering specificity, size of the market, fear of trace contaminants, and herbicide resistance in weeds. Also summarizes some successful herbicides, providing a table listing mode of action of some herbicides used for control of aquatic plants. (JN)

Martin, Dean F.; Martin, Barbara B.

1985-01-01

186

Clover as a cover crop for weed suppression in an intercropping design  

Microsoft Academic Search

Weeds often form a major problem in weakly competitive vegetable crops, particularly in low input systems. Undersown cover crops can be used to suppress weeds, but often put too high a competitive pressure on the main crop. Cover crop selection is one of the potential means that can be used to design or optimize these intercropping systems. The objective of

N. G. den Hollander; L. Bastiaans; M. J. Kropff

2007-01-01

187

Intercropping Leafy Greens and Maize on Weed Infestation, Crop Development, and Yield  

Microsoft Academic Search

Weed control in the tropics accounts for a large proportion of the total effort spent on cultivation. Experiments were conducted to investigate effects of time of establishment of leafy greens on their yields, weed control, and growth and yield of maize (Zea mays L.) in an intercrop. Amaranthus and Celosia were separately established as intercrops with maize on the same

Eyitayo A. Makinde; Olukemi T. Ayoola; Esther A. Makinde

2009-01-01

188

75 FR 57496 - Notice of Proposed Supplementary Rule To Require the Use of Certified Noxious-Weed-Free Forage...  

Federal Register 2010, 2011, 2012, 2013

...the Use of Certified Noxious-Weed-Free Forage and Straw on Bureau of Land Management...Idaho to use certified noxious-weed-free forage and straw. Restoration, rehabilitation...projects also will be required to use weed-free straw bales and mulch for project...

2010-09-21

189

Evaluation of mulching, intercropping with Sesbania and herbicide use for weed management in dry-seeded rice ( Oryza sativa L.)  

Microsoft Academic Search

This study was conducted to evaluate the effects of intercropping Sesbania with dry-seeded rice up to its vegetative phase (Sesbania), mulching with wheat residue (mulch) and herbicides for managing weeds and optimising the yield of dry-seeded rice. The density of grass weeds was lower with the mulch at all stages of crop growth. Though the dry weight of grass weeds

Samar Singh; J. K. Ladha; R. K. Gupta; Lav Bhushan; A. N. Rao; B. Sivaprasad; P. P. Singh

2007-01-01

190

Turfgrass management and weed control without pesticides on football pitches in Denmark.  

PubMed

Management of turfgrass on football pitches without pesticides involves a considerable challenge for weed control. By improving conditions for grass growth by cultural practices, weeds may be repressed by stronger competition from the grass. A 3-year field trial on 37 football pitches investigated the effects of various cultural management practices on percentage grass, weed and bare ground, respectively. The trial included twelve different treatments, comprising different combinations of fertiliser level and cultural methods, including two types of spring-tine harrow, vertical cutting, over-seeding, and top-dressing. Some treatments resulted in significant differences in percentage grass and weed cover, but not in percentage bare ground. However, other factors, such as locality of the football pitch, zone on the pitch, month, year, playing frequency, cutting frequency and, particularly, ground cover at the beginning of the trial, also contributed considerably to the variation in ground cover, indicating that established weeds are difficult to eradicate. PMID:15198331

Larsen, Søren U; Kristoffersen, Palle; Fischer, Jørgen

2004-06-01

191

Weed suscepts of the potato yellow dwarf virus  

Microsoft Academic Search

Summary  Fifteen new weed suscepts of the potato yellow dwarf virus are reported.\\u000a \\u000a Limited evidence is presented which indicates thatChrysanthemum leucanthemum var.pinnatifidum may be a more important source of the potato yellow dwarf virus under field conditions than Medium Red clover.\\u000a \\u000a \\u000a \\u000a The presence of the yellow dwarf virus was demonstrated in naturally infected plants of the following species:Chrysanthemum leucanthemum var.pinnatifidum, Trifolium

S. G. Younkin

1942-01-01

192

Development of a multispectral imagery device devoted to weed detection  

NASA Astrophysics Data System (ADS)

Multispectral imagery is a large domain with number of practical applications: thermography, quality control in industry, food science and agronomy, etc. The main interest is to obtain spectral information of the objects for which reflectance signal can be associated with physical, chemical and/or biological properties. Agronomic applications of multispectral imagery generally involve the acquisition of several images in the wavelengths of visible and near infrared. This paper will first present different kind of multispectral devices used for agronomic issues and will secondly introduce an original multispectral design based on a single CCD. Third, early results obtained for weed detection are presented.

Vioix, Jean-Baptiste; Douzals, Jean-Paul; Truchetet, Frederic; Navar, Pierre

2003-04-01

193

Complete genome sequences of two begomoviruses infecting weeds in Venezuela.  

PubMed

The complete sequences of isolates of two new bipartite begomoviruses (genus Begomovirus, family Geminiviridae) found infecting weeds in Venezuela are provided. The names proposed for these new begomoviruses are "Datura leaf distortion virus" (DLDV), isolated from a Datura stramonium L. (family Solanaceae) plant, and "Dalechampia chlorotic mosaic virus" (DCMV), isolated from infected Dalechampia sp. (family Euphorbiaceae) and Boerhavia diffusa L. (family Nyctaginaceae) plants. Phylogenetic analysis showed that these new begomoviruses segregated in two distinct clades of New World begomoviruses. To our knowledge, this is the first record of a begomovirus infecting Dalechampia sp. plants. Also, this is the first report of a begomovirus infecting Boerhavia spp. and Datura spp. in Venezuela. PMID:22926716

Fiallo-Olivé, Elvira; Chirinos, Dorys T; Geraud-Pouey, Francis; Moriones, Enrique; Navas-Castillo, Jesús

2013-01-01

194

Volatile Metabolites Controlling Germination in Buried Weed Seeds  

PubMed Central

Velvetleaf (Abutilon theophrasti Medic), morning glory (Ipomoea purpurea [L.] Roth), and wild mustard (Brassica kaber [D.C.] L. C. Wheeler) seeds exhibited decreased germination with increased planting depth in soil. Flushing the soil for 2 minutes each day with air overcame the inhibition. A sealed in vitro system was used to sample the volatile components produced by weed seeds. Inhibition of seed germination was accompanied by decreased O2 levels and production of volatile metabolites identified as acetaldehyde, ethanol, and acetone. The effectiveness of these compounds in reducing germination was dependent on O2 levels.

Holm, Robert E.

1972-01-01

195

Effects of hand weeding strip and nitrogen fertilizer on corn plants.  

PubMed

The objective of the present research was to evaluate effects of different strip weed control associated with nitrogen fertilizer on corn applied after planting. The experiment was set and conducted in Botucatu, São Paulo State, Brazil, and the hybrid planted was Dekalb 333-B. A completely randomized block design with four replications was used. Experimental plots were disposed as a factorial scheme 2 x 2 x 4, constituted by two types of weeding on row (with or without manual hoeing), two types of weeding on inter-row (with or without manual hoeing), and four nitrogen levels applied after planting (00, 60, 90, and 120 kg ha(-1)). Plots were composed by six rows with 5 m length. Nitrogen fertilizer was applied at 35 days after emergence (d.a.e). For weed community it was evaluated: weed density, dominancy, frequency, and relative importance. The main weed species were: Brachiaria plantiginea, Amaranthus retroflexus, Bidens pilosa, Cyperus rotunds, Brachiaria decumbens, Euphorbia heterofila, Oxalis latifolia, Acanthospermum hispidum, Commelina benghalensis. It was evaluated corn height at 40 and 100 d.a.e., first ear insertion height at 100 d.a.e., and final grain yield at harvesting. Plants and first ear insertion height were affected when nitrogen fertilizer was not applied. Treatments without weed control showed that weed interfered negatively with plants height. There were no correlation between weeds and nitrogen fertilizer for all parameters evaluated. Parcels without weed showed the highest ear weights and final grain production. Treatments that received nitrogen fertilizer, independently of studied arrangement, provided higher yields. PMID:15656170

da Silva, João Renato Vaz; Martins, Dagoberto; Cardoso, Leonildo A; Carbonari, Caio Antonio

2005-01-01

196

Weed vegetation ecology of arable land in Salalah, Southern Oman.  

PubMed

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

El-Sheikh, Mohamed A

2013-07-01

197

The Use of Protein Hydrolysates for Weed Control  

NASA Astrophysics Data System (ADS)

Corn gluten meal, the protein fraction of corn (Zea mays L.) grain, is commercially used as a natural weed control agent and nitrogen source in horticultural crops and in the turf and ornamental markets. Corn gluten hydrolysate, a water soluble form of gluten meal, has also been proposed for the same purpose, although it could be sprayed on the soil rather than applied in the granular form. Five depeptides, glutaminyl-glutamine (Gln-Gln), glycinyl-alanine (Gly-Ala), alanyl-­glutamine (Ala-Glu), alanyl-asparagine (Ala-Asp), and alaninyl-alanine (Ala-Ala) and a pentapeptide leucine-serine-proline-alanine-glutamine (Leu-Ser-Pro-Ala-Gln) were identified as the active components of the hydrolysate. Microscopic analysis revealed that Ala-Ala acted on some metabolic process rather than directly on the mitotic apparatus. Similar to the chloracetamides and sulfonyl-urea hebicides, Ala-Ala inhibits cell division rather than disrupting of cell division processes. Cellular ultrastructure changes caused by exposure to Ala-Ala implicate Ala-Ala as having membrane-disrupting characteristics similar to several synthetic herbicides. The potential use of the hydrolysate and the peptides as weed controls is discussed.

Christians, Nick; Liu, Dianna; Unruh, Jay Bryan

198

Weed vegetation ecology of arable land in Salalah, Southern Oman  

PubMed Central

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.

El-Sheikh, Mohamed A.

2013-01-01

199

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

PubMed

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. PMID:18817174

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

2008-02-01

200

Climate Effects and Feedback Structure Determining Weed Population Dynamics in a Long-Term Experiment  

PubMed Central

Pest control is one of the areas in which population dynamic theory has been successfully applied to solve practical problems. However, the links between population dynamic theory and model construction have been less emphasized in the management and control of weed populations. Most management models of weed population dynamics have emphasized the role of the endogenous process, but the role of exogenous variables such as climate have been ignored in the study of weed populations and their management. Here, we use long-term data (22 years) on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes (local and large-scale climate factors). Our modeling study determined two different feedback structures and climate effects in the two weed species analyzed. While Descurainia sophia exhibited a second-order feedback and low climate influence, Veronica hederifolia was characterized by a first-order feedback structure and important effects from temperature and rainfall. Our results strongly suggest the importance of theoretical population dynamics in understanding plant population systems. Moreover, the use of this approach, discerning between the effect of exogenous and endogenous factors, can be fundamental to applying weed management practices in agricultural systems and to controlling invasive weedy species. This is a radical change from most approaches currently used to guide weed and invasive weedy species managements.

Lima, Mauricio; Navarrete, Luis; Gonzalez-Andujar, Jose Luis

2012-01-01

201

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

PubMed Central

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.

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

2013-01-01

202

Accuracy and Feasibility of Optoelectronic Sensors for Weed Mapping in Wide Row Crops  

PubMed Central

The main objectives of this study were to assess the accuracy of a ground-based weed mapping system that included optoelectronic sensors for weed detection, and to determine the sampling resolution required for accurate weed maps in maize crops. The optoelectronic sensors were located in the inter-row area of maize to distinguish weeds against soil background. The system was evaluated in three maize fields in the early spring. System verification was performed with highly reliable data from digital images obtained in a regular 12 m × 12 m grid throughout the three fields. The comparison in all these sample points showed a good relationship (83% agreement on average) between the data of weed presence/absence obtained from the optoelectronic mapping system and the values derived from image processing software (“ground truth”). Regarding the optimization of sampling resolution, the comparison between the detailed maps (all crop rows with sensors separated 0.75 m) with maps obtained with various simulated distances between sensors (from 1.5 m to 6.0 m) indicated that a 4.5 m distance (equivalent to one in six crop rows) would be acceptable to construct accurate weed maps. This spatial resolution makes the system cheap and robust enough to generate maps of inter-row weeds.

Andujar, Dionisio; Ribeiro, Angela; Fernandez-Quintanilla, Cesar; Dorado, Jose

2011-01-01

203

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

NASA Astrophysics Data System (ADS)

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%.

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

2012-02-01

204

Community assembly and biomass production in regularly and never weeded experimental grasslands  

NASA Astrophysics Data System (ADS)

We studied the natural colonisation of new species in experimental grasslands varying in plant species richness (from 1 to 60) and plant functional group richness (from 1 to 4) in either regularly or never weeded subplots during the first 3 years after establishment. Sown species established successfully, with no differences in species richness or their relative abundances between the regularly and never weeded subplots during the study period. Aboveground biomass of sown species increased with increasing sown species richness in both treatments. While a positive relationship between sown species richness and total aboveground biomass (including colonising species) existed in the 2nd year after sowing in the regularly and never weeded subplots, this positive relationship decayed in the 3rd year in the never weeded subplots because of a higher biomass of colonising species in species-poor mixtures. Total aboveground biomass varied independently of total species richness 3 years after sowing in both treatments. Jaccard similarity of coloniser species composition between regularly and never weeded subplots decreased from the 2nd to the 3rd year, indicating a divergence in coloniser species composition. Coloniser immigration and turnover rates were higher in regularly weeded subplots, confirming that weeding counteracts species saturation and increases the chance that new colonisers would establish. Although our study shows that low diversity plant communities are unstable and converge to higher levels of biodiversity, the effects of initially sown species on community composition persisted 3 years after sowing even when allowing for succession, suggesting that colonising species mainly filled empty niche space.

Roscher, Christiane; Temperton, Vicky M.; Buchmann, Nina; Schulze, Ernst-Detlef

2009-03-01

205

Breeding cereal crops for enhanced weed suppression: optimizing allelopathy and competitive ability.  

PubMed

Interest in breeding grain crops with improved weed suppressive ability is growing in response to the evolution and rapid expansion of herbicide resistant populations in major weeds of economic importance, environmental concerns, and the unmet needs of organic producers and smallholder farmers without access to herbicides. This review is focused on plant breeding for weed suppression; specifically, field and laboratory screening protocols, genetic studies, and breeding efforts that have been undertaken to improve allelopathy and competition in rice, wheat, and barley. The combined effects of allelopathy and competition determine the weed suppressive potential of a given cultivar, and research groups worldwide have been working to improve both traits simultaneously to achieve maximum gains in weed suppression. Both allelopathy and competitive ability are complex, quantitatively inherited traits that are heavily influenced by environmental factors. Thus, good experimental design and sound breeding procedures are essential to achieve genetic gains. Weed suppressive rice cultivars are now commercially available in the U.S. and China that have resulted from three decades of research. Furthermore, a strong foundation has been laid during the past 10 years for the breeding of weed suppressive wheat and barley cultivars. PMID:23385368

Worthington, Margaret; Reberg-Horton, Chris

2013-02-01

206

Weed response to herbicides: regional-scale distribution of herbicide resistance alleles in the grass weed Alopecurus myosuroides.  

PubMed

Effective herbicide resistance management requires an assessment of the range of spatial dispersion of resistance genes among weed populations and identification of the vectors of this dispersion. In the grass weed Alopecurus myosuroides (black-grass), seven alleles of the acetyl-CoA carboxylase (ACCase) gene are known to confer herbicide resistance. Here, we assessed their respective frequencies and spatial distribution on two nested geographical scales (the whole of France and the French administrative district of Côte d'Or) by genotyping 13 151 plants originating from 243 fields. Genetic variation in ACCase was structured in local populations at both geographical scales. No spatial structure in the distribution of resistant ACCase alleles and no isolation by distance were detected at either geographical scale investigated. These data, together with ACCase sequencing and data from the literature, suggest that evolution of A. myosuroides resistance to herbicides occurred at the level of the field or group of adjacent fields by multiple, independent appearances of mutant ACCase alleles that seem to have rather restricted spatial propagation. Seed transportation by farm machinery seems the most likely vector for resistance gene dispersal in A. myosuroides. PMID:16918556

Menchari, Yosra; Camilleri, Christine; Michel, Séverine; Brunel, Dominique; Dessaint, Fabrice; Le Corre, Valérie; Délye, Christophe

2006-01-01

207

Weeds Gone Wild: Alien Plant Invaders of Natural Areas  

NSDL National Science Digital Library

Weeds Gone Wild is a project of Plant Conservation Alliance (reviewed in the January 19, 2000 Scout Report for Science & Engineering-- http://scout.cs.wisc.edu/report/sci-eng/2000/se-000119.html#16}), a consortium of federal and non-federal agencies dedicated to protecting native plants. Targeting viewers ranging from the general public to researchers, this site provides information on "the serious threat and impacts of invasive alien (exotic, non-native) plants to the native flora, fauna, and natural ecosystems of the United States." To that end, the site includes a compiled national list of many invasive plants (Aquatics, Herbs, Vines, Shrubs and Trees); comprehensive background information on invasive species; illustrated fact sheets with plant descriptions, native range, distribution, and habitat in the US; management options and suggested alternative native plants; and other information. A collection of links of experts and organizations rounds out this well-conceived site.

208

Optical parameters of leaves of seven weed species  

NASA Technical Reports Server (NTRS)

The absorption coefficient (k), infinite reflectance (R), and scattering coefficient (s) were tabulated for five wavelengths and analyzed for statistical differences for seven weed species. The wavelengths were: 0.55-micrometer, 0.65-micrometers, 0.85-micrometer, 1.65-micrometers, and 2.20-micrometer. The R of common lambsquarters (Chenopodium album L.), Johnsongrass (Sorghum halepense (L.) Pers.), and annual sowthistle (Sonchus oleraceus L.) leaves at the 0.85-micrometer wavelength were significantly (p=0.05) higher than for sunflower (Heliantus annus L.), ragweed parthenium (Parthenium hysterophorus L.), or London rocket (Sisymbrium irio L.). Annual sowthistle had the largest k value, and Plamer amaranth (Amaranthus palmer S. Wats.) had the smallest k value at the 0.65 approximately chlorophyll absorption wavelength. In general, john-songress, ragweed parthenium, or London rocket had the largest s values among the five wavelengths, wereas annual sowthistle and plamar amaranth were usually lowest.

Gausman, H. W.; Menges, R. M.; Richardson, A. J.; Walter, H.; Rodriguez, R. R.; Tamez, S. (principal investigators)

1982-01-01

209

Optical parameters of leaves of seven weed species  

NASA Technical Reports Server (NTRS)

Absorption coefficient (k), infinite reflectance (R inf.) and scattering coefficient (s) were tabulated for five wavelengths and analyzed for statistical differences for seven weed species. The wavelengths were: 0.55, 0.65, 0.85, 1.65, and 2.20 microns. The R inf. of common lambsquarters (Chenopodium album L.), johnsongrass (Sorghum halepense L. Pers.), and annual sowthistle (Sonchus oleraceus L.) leaves at the 0.85 micron wavelength were significantly (p = 0.05) higher than for sunflower (Helianthus annuus L.), ragweed parthenium (parthenium hysterophorus L.), or London rocket (Sisymbrium irio L.). Annual sowthistle had the largest k value, and Palmer amaranth (Amaranthus palmeri S. Wats.) had the smallest k value at the 0.65 micron chlorophyll absorption wavelength. In general, johnsongrass, ragweed parthenium, and London rocket had the largest s values among the five wavelengths, whereas annual sowthistle and Palmer amaranth were usually lowest.

Gausman, H. W.; Menges, R. M.; Richardson, A. J.; Walter, H.; Rodriguez, R. R.; Tamez, S. (principal investigators)

1982-01-01

210

Unearthing the impact of human disturbance on a notorious weed.  

PubMed

Large-scale anthropogenic changes in the environment are reshaping global biodiversity and the evolutionary trajectory of many species. Evolutionary mechanisms that allow organisms to thrive in this rapidly changing environment are just beginning to be investigated (Hoffmann & Sgrò 2011; Colautti & Barrett 2013). Weedy and invasive species represent 'success stories' for how species can cope with human modified environments. As introduced species have spread within recent times, they provide the unique opportunity to track the genetic consequences of rapid range expansion through time and space using historic DNA samples. Using modern collections and herbarium specimens dating back to 1873, Martin et al. (2014) have provided a more complete understanding of the population history of the invasive, agricultural weed, common ragweed (Ambrosia artemisiifolia; Fig. 1) in its native range with surprising results. They find that the recent population explosion of common ragweed in North America coincided with substantial shifts in population genetic structure with implications for invasion. PMID:24766630

Hodgins, Kathryn

2014-05-01

211

Herbicide-resistant weeds: from research and knowledge to future needs  

PubMed Central

Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge.

Busi, Roberto; Vila-Aiub, Martin M; Beckie, Hugh J; Gaines, Todd A; Goggin, Danica E; Kaundun, Shiv S; Lacoste, Myrtille; Neve, Paul; Nissen, Scott J; Norsworthy, Jason K; Renton, Michael; Shaner, Dale L; Tranel, Patrick J; Wright, Terry; Yu, Qin; Powles, Stephen B

2013-01-01

212

Phytotoxicity of Cardoon (Cynara cardunculus) Allelochemicals on Standard Target Species and Weeds.  

PubMed

Cardoon (Cynara cardunculus L.) is a native plant to the Iberian Peninsula and the European Atlantic coast and invasive in American environments. Different solvents were used to perform cardoon extracts that were tested in phytotoxic bioassays. The ethyl acetate extract had the highest inhibitory activity so this was tested on the germination and growth of standard target species (lettuce, watercress, tomato, and onion) and weeds (barnyardgrass and brachiaria). The ethyl acetate extract was very active on root growth in both standard target species and weeds and it was therefore fractionated by chromatography. The spectroscopic data showed that the major compounds were sesquiterpene lactones. Aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The presence of these compounds explains the bioactivity of the ethyl acetate extract. The strong phytotoxicity of these compounds on important weeds shows the potential of these compounds as natural herbicide models. PMID:24974850

Rial, Carlos; Novaes, Paula; Varela, Rosa M; G Molinillo, José M; Macias, Francisco A

2014-07-16

213

Engineering phosphorus metabolism in plants to produce a dual fertilization and weed control system.  

PubMed

High crop yields depend on the continuous input of orthophosphate (PO(4)(?3))-based fertilizers and herbicides. Two major challenges for agriculture are that phosphorus is a nonrenewable resource and that weeds have developed broad herbicide resistance. One strategy to overcome both problems is to engineer plants to outcompete weeds and microorganisms for limiting resources, thereby reducing the requirement for both fertilizers and herbicides. Plants and most microorganisms are unable to metabolize phosphite (PO(3)(?3)), so we developed a dual fertilization and weed control system by generating transgenic plants that can use phosphite as a sole phosphorus source. Under greenhouse conditions, these transgenic plants require 30–50% less phosphorus input when fertilized with phosphite to achieve similar productivity to that obtained by the same plants using orthophosphate fertilizer and, when in competition with weeds, accumulate 2–10 times greater biomass than when fertilized with orthophosphate. PMID:22922674

López-Arredondo, Damar Lizbeth; Herrera-Estrella, Luis

2012-09-01

214

Aquatic Plant Control Program. Technical Report 8. Aquatic Weed Control with Plant Pathogens.  

National Technical Information Service (NTIS)

Under a research contract all of the major lakes and rivers of Florida have been surveyed for diseases of water hyacinths (Eichhornia crassipes), alligator weed (Alternanthera philoxeroides), Eurasian water milfoil (Myriophyllum spicatum), and hydrilla (H...

E. O. Gangstad T. E. Freeman F. W. Zettler R. E. Rintz R. Charudattan

1974-01-01

215

Classification of Weed Species Using Artificial Neural Networks Based on Color Leaf Texture Feature  

NASA Astrophysics Data System (ADS)

The potential impact of herbicide utilization compel people to use new method of weed control. Selective herbicide application is optimal method to reduce herbicide usage while maintain weed control. The key of selective herbicide is how to discriminate weed exactly. The HIS color co-occurrence method (CCM) texture analysis techniques was used to extract four texture parameters: Angular second moment (ASM), Entropy(E), Inertia quadrature (IQ), and Inverse difference moment or local homogeneity (IDM).The weed species selected for studying were Arthraxon hispidus, Digitaria sanguinalis, Petunia, Cyperus, Alternanthera Philoxeroides and Corchoropsis psilocarpa. The software of neuroshell2 was used for designing the structure of the neural network, training and test the data. It was found that the 8-40-1 artificial neural network provided the best classification performance and was capable of classification accuracies of 78%.

Li, Zhichen; An, Qiu; Ji, Changying

216

Weed Use Up, Cocaine Use Down, U.S. Report Finds  

MedlinePLUS

... this page, please enable JavaScript. Weed Use Up, Cocaine Use Down, U.S. Report Finds Review covered 2000 ... March 10, 2014 (HealthDay News) -- Americans' use of cocaine fell by half from 2006 to 2010, but ...

217

Effect of pre-planting irrigation, maize planting pattern and nitrogen on weed seed bank population.  

PubMed

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. PMID:22696965

Hemmati, E; Vazan, S; Oveisi, M

2011-01-01

218

Evaluation of herbicides for weed control in irrigated garlic ( Allium sativum L.) at Samaru, Nigeria  

Microsoft Academic Search

Field trials were carried out during the dry seasons of 1995 and 1996 to identify suitable pre-emergence herbicides for weed control in garlic (Allium sativum L.) at Samaru, Nigeria. All the herbicide treatments tested effectively reduced weed infestation compared with the weedy control. Garlic plant height and shoot dry matter were depressed by oxadiazon plus cinosulfuron at 0.75+0.02kga.i.\\/ha, oxadiazon plus

Peter Tunku; S. T. O. Lagoke; D. B. Ishaya

2007-01-01

219

Response of upland rice cultivars to weed competition in the savannas of West Africa  

Microsoft Academic Search

A 2-year field study was conducted to assess the effect of weed competition on the performance of upland rice cultivars in the savannas of Nigeria. A split-plot design was used with three weeding levels as the main plot treatments and the rice cultivars CG 14, ITA 150, WAB 56-104, NERICA1, NERICA2, and NERICA4 as the subplots. Grain yield, spikelets plant?1

Friday Ekeleme; Alpha Y. Kamara; Sylvester O. Oikeh; Lucky O. Omoigui; Paul Amaza; Tahirou Abdoulaye; David Chikoye

2009-01-01

220

The effect of natural weed buffers on soil and nitrogen losses in Japan  

Microsoft Academic Search

In Japan, heavy rains from June to October cause severe erosion in the agricultural fields. Natural weed buffers may help conserve the soil and water. We measured the mass balances of the water, soil and nitrogen components in a plot of 159 m2 (7.2 m wide and 22.1 m long). Plant growth in the plot was dominated by the weeds

Machito Mihara

2006-01-01

221

Invasive Freshwater Macrophyte Alligator Weed: Novel Adsorbent for Removal of Malachite Green from Aqueous Solution  

Microsoft Academic Search

The batch sorption experiments were carried out using a novel adsorbent, freshwater macrophyte alligator weed, for the removal\\u000a of basic dye malachite green from aqueous solution. Effects of process parameters such as initial solution pH, contact time,\\u000a adsorbent concentration, particle size, and ion strength were investigated. The adsorbent was characterized by FT-IR. The\\u000a adsorption of malachite green by alligator weed

Xue Song Wang

2010-01-01

222

Bidens pilosa L. Exhibits High Sensitivity to Coumarin in Comparison with Three Other Weed Species  

Microsoft Academic Search

Nine natural plant compounds were screened for phytotoxicity to Bidens pilosa L. a troublesome weed in field and plantation crops. The sensitivity of three other weed species to coumarin, the most active\\u000a identified compound, was also evaluated. Coumarin, at a concentration of 500 ?M, had little effect on germination and growth\\u000a of Senna obtusifolia L., Euphorbia heterophylla L., and Ipomoea grandifolia

Érica Marusa Pergo; Denise Abrahim; Patrícia Cristina Soares da Silva; Kátia Aparecida Kern; Lucas Jonatas Da Silva; Elemar Voll; Emy Luiza Ishii-Iwamoto

2008-01-01

223

Methods for selecting hypervirulent biocontrol agents of weeds: why and how.  

PubMed

A considerable number of plant pathogens have been studied for their possible use in weed control. Some have proven virulent enough to control weed species and to compete commercially with chemical herbicides. However, most pathogens of weeds are not useful in their wild form because they are not sufficiently host-specific and/or virulent. The authors believe that these barriers can be overcome. The present research has focused on the inhibitory effects of certain amino acids on the growth and development of specific plants. Pathogens that overproduce these selected amino acids can be easily selected from a pool of spontaneous mutants. Such mutants can have increased pathogenicity to their target weed and enhanced field performance as biocontrol agents. Enhancement of biocontrol efficacy in three separate pathogen-host systems, two with Fusarium and one with Pseudomonas, has already been reported. It is proposed to use the same technology to enhance the biocontrol efficacy of the two species of Fusarium that are host-specific pathogens of the broomrape group of parasitic weeds. The stepwise approach outlined can lead to obtaining enhanced biocontrol agents capable of producing inhibitory levels of selected amino acids in situ. It is proposed that these approaches, in combination with other methods of virulence enhancement, will lead to sustainable systems of biological control of parasitic weeds. PMID:19288472

Sands, David C; Pilgeram, Alice L

2009-05-01

224

[Research on crop-weed discrimination using a field imaging spectrometer].  

PubMed

Discrimination of weeds from crop is the first and important step for variable herbicides application and precise physical weed control. Using a new field imaging spectrometer developed by our group, hyperspectral images in the wavelength range 380-870 nm were taken in the wild for the investigation of crop-weed discrimination. After normalizing the data to reduce or eliminate the influence of varying illuminance, stepwise forward variable selection was employed to select the proper band sets and fisher linear discriminant analysis (LDA) was performed to discriminate crop and weeds. For the case of considering each species as a different class, classification accuracy reached 85% with eight selected bands while for the case of considering overall weed species as a class, classification accuracy was higher than 91% with seven selected bands. In order to develop a low-cost device and system in future, all combinations of two and three bands were evaluated to find the best combinations. The result showed that the best three bands can achieve a performance of 89% comparable to the performance achieved by five bands selected using stepwise selection. The authors also found that "red edge" could afford abundant information in the discrimination of weed and crop. PMID:20827980

Liu, Bo; Fang, Jun-yong; Liu, Xue; Zhang, Li-Fu; Zhang, Bing; Tong, Qing-xi

2010-07-01

225

Remote sensing to monitor monotypic weed patches in semi-arid grasslands  

NASA Astrophysics Data System (ADS)

Remote sensing technology has great potential for mapping weed distributions. Fine-scale weed distribution maps can provide means to evaluate the success of weed control methods, to guide selection of future control methods, and to examine factors that influence the creation and persistence of monotypic weed patches. Here I examined the effectiveness of different classification approaches in detecting dense monotypic patches of the late-phenology weeds Taeniatherum caput-medusae (medusahead) and Aegilops triuncialis (barbed goatgrass), among cool-season forage grasses (Bromus spp. and Avena spp.) across multiple years in semi-arid rangelands in northern California (USA). I found that color infrared photographs acquired at two key phenological periods produced more accurate classifications than those based on one image alone, and that inclusion of training sites did not improve the overall accuracy of a classification. I also examined the association of remnant litter with transitions in species dominance in medusahead, goatgrass or forage patches. Persistence of goatgrass-dominated patches was correlated with the amount of remnant litter present, but surprisingly that of medusahead was not, suggesting a potential need for different strategies in control of these two noxious species. Overall, this study shows that remote sensing can be used to create weed distribution maps of phenologically distinct species, and help us further understand community response to invasion and evaluate the effectiveness of management treatments.

Planck, Laura

226

Effect of cultivation on allelopathic interference success of the weed,Pluchea lanceolata.  

PubMed

Pluchea lanceolata, a perennial noxious weed, is rapidly spreading into cultivated fields in semiarid regions of India. The objective of the present study was to evaluate the effect of cultivation on the interference success ofPluchea lanceolata by comparing chemical characteristics of the weed and its associated topsoil and subsoil in cultivated and uncultivated habitats. Weed plants from both cultivated and uncultivated habitats were analyzed for four biotic characteristics. Leaves were analyzed for nine chemical characteristics. Soils (topsoil and subsoil) were analyzed for 13 chemical characteristics. Nutrient concentrations of the weed and its associated soils, both in cultivated and uncultivated habitats, showed that plant response with reference to nutrient uptake was inversely related to that of soils. Thus, the weed does not create nutrient stress. With cultivation, leaf area and Cu and Na contents increased, while leaf ash, leaf weight, and Mg and Ca decreased. In the topsoil and subsoil, however, concentrations of total carbonates, total phenolics, and Ca increased with cultivation, while organic carbon, phosphate, and K decreased. High phenolic content of the cultivated fields could be explained due to leaching of water-soluble compounds from the plant parts either through natural leaching or through various agricultural practices such as ploughing and irrigation. We concluded that water-soluble phenolics, leached from the weed into the soil, increased with cultivation. PMID:24242313

Inderjit; Dakshini, K M

1994-05-01

227

Determination of fungal pathogens of common weed species in the vicinity of Tokat, Turkey.  

PubMed

This study was carried out to determine the fungal pathogens on Chenopodium album L., Cirsium arvense (L.) Scop., Convolvulus arvensis L., Cynodon dactylon (L.) Pers., Delphinium consolida L., Portulaca oleracea L., Rumex crispus L., Solanum nigrum L., Sorghum halepense (L.) Pers. and Xanthium strumarium L. which were common weed species of agricultural areas. Surveys were conducted in May-June and August-September in 2004-2005 growing seasons. During the surveys density and frequency of the above mentioned weed species were also determined and number of infected plants was counted in each sampling area. Infected weed samples were collected from each sampling point and brought to the laboratory in polyethylene bags and the pathogens were identified at genus or species level. As a result of two year surveys, ten fungal pathogens were determined on eight weed species. The most important fungal pathogens determined on common weed species were as follow; Peronospora farinosa (Fr.) Fr. on C. album, and Septoria convolvuli DC., Erysiphe convolvuli DC., and Puccinia punctiformis (Strauss) Roehrl. on C. arvensis. These fungal diseases were observed mainly on the weeds located at the borders of fields. Infection rates of these pathogens reached up to 21.2% in some of the survey areas. Further studies should be conducted to evaluate the efficacy of these pathogen under in vitro and in vivo conditions. PMID:21542473

Kadio?lu, I; Karamanli, N; Yanar, Y

2010-01-01

228

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

PubMed Central

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.

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

2012-01-01

229

Cover Crop Residue and Organic Mulches Provide Weed Control during Limited-Input No-Till Collard Production  

Microsoft Academic Search

Limited input producers may adopt no-till production if sufficient weed suppression can be achieved. High-biomass producing cover crops used in conjunction with organic mulches may provide sufficient weed control in no-till vegetable production. Our objective was to quantify weed suppression from a forage soybean summer cover crop and three types of organic mulches applied after collard (Brassica oleracea L.) planting.

Michael J. Mulvaney; Andrew J. Price; C. Wesley Wood

2011-01-01

230

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

PubMed Central

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.

Pena, Jose Manuel; Torres-Sanchez, Jorge; de Castro, Ana Isabel; Kelly, Maggi; Lopez-Granados, Francisca

2013-01-01

231

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

PubMed

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. PMID:24146963

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

2013-01-01

232

Prospects for the Management of Invasive Alien Weeds Using Co-Evolved Fungal Pathogens: A Latin American Perspective  

Microsoft Academic Search

Invasive alien weeds pose a serious threat to the biodiversity of natural ecosystems and a significant constraint to agricultural\\u000a production worldwide. The use of co-evolved natural enemies, a strategy referred to as classical biological control (CBC),\\u000a has proven to be a potentially efficacious, cost-effective, and safe option for the management of alien weeds. An analysis\\u000a of CBC of invasive weeds

Carol A. Ellison; Robert W. Barreto

2004-01-01

233

Effect of Bio-organic Fertilization and Some Weed Control Treatments on Yield and Yield Components of Wheat  

Microsoft Academic Search

2 Abstract: Two field experiments were carried out during winter seasons 2004\\/2005 and 2005\\/2006 in th e Experimental Station of National Research Centre, Shalakan District, Kalubia Governorate, Egypt. The investigation aimed to study the response of wheat cultivar Sakha-93 to three weed control treatments 1-Unweeded (control),2-Hand weeding twice at 30 and 60 DAS 3-Chemical weed control by Panther 55% Sc

G. A. Sary; H. M. El-Naggar; M. O. Kabesh

234

Fungal pathogens of Euphorbia heterophylla and E. hirta in Brazil and their potential as weed biocontrol agents  

Microsoft Academic Search

A two-year survey of the fungi associated with two important congeneric pantropical weeds, Euphorbia heterophylla and E. hirta, was conducted in part of their native range in southern Brazil. Sampling was concentrated mainly in Rio de Janeiro State\\u000a and ten species were identified as pathogens of these weeds. Two taxa, Botrytis ricini and Uromyces euphorbiae, were common to both weed

Robert W. Barreto; Harry C. Evans

1998-01-01

235

The role of weed invasion in controlling sand dune reactivation in abandoned fields in semi-arid Inner Mongolia, China  

Microsoft Academic Search

The growth of crops and invading weeds were examined at six sites under different cultivation conditions in semi-arid Inner\\u000a Mongolia, where sand dune reactivation has been controlled by weed invasion. The soil moisture content was not sufficient\\u000a for crop growth in over-cultivated farmland. The shortage of moisture in the soil suppresses the growth of both crops and\\u000a weeds. Accordingly, farmers

Masayuki Nemoto; Toshiya Ohkuro; Bin Xu

1997-01-01

236

Selenium concentrations of common weeds and agricultural crops grown in the seleniferous soils of northwestern India.  

PubMed

The plants grown in seleniferous soils constitute a major source of toxic selenium levels in the food chain of animals and human beings. Greenhouse and field experiments were conducted to study selenium concentrations of weeds, forages and cereals grown on seleniferous soils located between 31.0417 degrees to 31.2175 degrees N and 76.1363 degrees to 76.4147 degrees E in northwestern India. Eleven winter season (November-April) weed plants were grown in the greenhouse in a soil treated with different levels of selenate-Se. Selenium concentrations of weed plants increased progressively with the levels of selenate-Se in soil. The highest Se concentration was recorded by Silene gallica (246 mgkg(-1)) and the lowest by Avena ludoviciana (47 mgkg(-1)) at 2.5 mg Sekg(-1) soil. A.ludoviciana and Spergula arvensis proved highly tolerant to the presence of 1.25 and 2.5 mg selenate-Sekg(-1) soil and the remaining weeds were sensitive to Se. Dry matter yield of Se-sensitive weed plants was 25 to 62% of the yield in the no-Se control at 1.25mg selenate-Sekg(-1) and 6 to 40% at 2.5mg selenate-Sekg(-1) soil. Other symptoms like change in leaf colour and size, burning of leaf tips and margins, and delayed flowering were also observed due to Se. Dry matter yield of Se-sensitive weed plants expressed as percentage of yield in the no-Se control at both the Se levels was inversely correlated with their Se content (r=-0.731, p<0.01, N=17). Among the weed plants grown in seleniferous soils under field situations, Mentha longifolia accumulated the highest Se (365 mgkg(-1)) and Phalaris minor the lowest (34 mgkg(-1)). Among agricultural crops grown on a naturally contaminated soil in the greenhouse, Se concentrations were the highest for oilseed crops (19-29 mgkg(-1)), followed by legumes (6-13 mgkg(-1)) and cereals (2-18 mgkg(-1)). Helianthus annuus among the oilseed crops, A.ludoviciana among the winter season weeds, M.longifolia among the summer season (May-October) weeds and Cirsium arvense among the perennial weeds can be used for phytoremediation of seleniferous soils as these accumulate the highest amounts of Se. PMID:19800657

Dhillon, Karaj S; Dhillon, Surjit K

2009-12-01

237

[Effects of different multiple cropping systems on paddy field weed community under long term paddy-upland rotation].  

PubMed

Based on a long term field experiment, this paper studied the effects of different multiple cropping systems on the weed community composition and species diversity under paddy-upland rotation. The multiple cropping rotation systems could significantly decrease weed density and inhibited weed growth. Among the rotation systems, the milk vetch-early rice-late maize --> milk vetchearly maize intercropped with early soybean-late rice (CCSR) had the lowest weed species dominance, which inhibited the dominant weeds and decreased their damage. Under different multiple cropping systems, the main weed community was all composed of Monochoia vaginalis, Echinochloa crusgalli, and Sagittaria pygmae, and the similarity of weed community was higher, with the highest similarity appeared in milk vetch-early rice-late maize intercropped with late soybean --> milk vetch-early maize-late rice (CSCR) and in CCSR. In sum, the multiple cropping rotations in paddy field could inhibit weeds to a certain extent, but attentions should be paid to the damage of some less important weeds. PMID:24417111

Yang, Bin-Juan; Huang, Guo-Qin; Xu, Ning; Wang, Shu-Bin

2013-09-01

238

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

PubMed

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. PMID:24517852

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

2014-04-01

239

Experimental Transmission of Pospiviroid Populations to Weed Species Characteristic of Potato and Hop Fields?  

PubMed Central

Weed plants characteristic for potato and hop fields have not been considered in the past as potential hosts that could transmit and lead to spreading of potato spindle tuber (PSTVd) and hop stunt (HSVd) viroids, respectively. To gain insight into this problem, we biolistically inoculated these weed plants with viroid populations either as RNA or as cDNA. New potential viroid host species, collected in central Europe, were discovered. From 12 weed species characteristic for potato fields, high viroid levels, detectable by molecular hybridization, were maintained after both RNA and DNA transfers in Chamomilla reculita and Anthemis arvensis. Low viroid levels, detectable by reverse transcription-PCR (RT-PCR) only, were maintained after plant inoculations with cDNA in Veronica argensis and Amaranthus retroflexus. In these two species PSTVd concentrations were 105 and 103 times, respectively, lower than in tomato as estimated by real-time PCR. From 14 weeds characteristic for hop fields, high HSVd levels were detected in Galinsoga ciliata after both RNA and DNA transfers. HSVd was found, however, not to be transmissible by seeds of this weed species. Traces of HSVd were detectable by RT-PCR in HSVd-cDNA-inoculated Amaranthus retroflexus. Characteristic monomeric (+)-circular and linear viroid RNAs were present in extracts from weed species propagating viroids to high levels, indicating regular replication, processing, and circularization of viroid RNA in these weed species. Sequence analyses of PSTVd progenies propagated in C. reculita and A. arvensis showed a wide spectrum of variants related to various strains, from mild to lethal variants; the sequence variants isolated from A. retroflexus and V. argensis exhibited similarity or identity to the superlethal AS1 viroid variant. All HSVd clones from G. ciliata corresponded to a HSVdg variant, which is strongly pathogenic for European hops.

Matousek, J.; Orctova, L.; Ptacek, J.; Patzak, J.; Dedic, P.; Steger, G.; Riesner, D.

2007-01-01

240

Can weed hosts increase aggressiveness of Phytophthora infestans on potato?  

PubMed

Potato late blight, caused by Phytophthora infestans, is a major disease in potato production throughout the world. In southern Sweden, hairy nightshade (Solanum physalifolium), an alternative non-crop host to the pathogen, is an increasing weed problem. Single-lesion leaves infected by P. infestans were collected from potato and hairy nightshade to determine phenotypic and genotypic population differentiation of P. infestans between the two hosts. Genotypic variation was estimated using microsatellites as markers. The results showed no genotypic differentiation in the samples between the two hosts. Aggressiveness tests were performed using the sampled isolates to cross-inoculate potato and hairy nightshade. The proportion of infected leaves, latency period, lesion growth rate, and sporulation capacity were measured. For isolates from hairy nightshade, the odds of infection were higher on both hosts combined. When tested on potato leaves, isolates from hairy nightshade showed a significantly shorter latency period and higher sporulation capacity compared with isolates from potato. This indicates that an alternative host can filter populations of P. infestans toward a higher aggressiveness, which could lead to increasing problems in controlling potato late blight. PMID:22185335

Grönberg, L; Andersson, B; Yuen, J

2012-04-01

241

Photosensitization in sheep fed Ammi majus (Bishop's weed) seed.  

PubMed

Ammi majus (bishop's weed) grows on the coastal region of southern United States and in other parts of the world. This plant causes severe photosensitization in livestock and probably contributes to the severe photosensitization outbreaks seen in Texas. Sheep were fed finely ground seed of A majus via stomach tube at dose rates of 1, 2, 4, and 8 g/kg of body weight and exposed to sunlight. The single dose of 8 g/kg produced severe clinical signs (in 24 to 48 hours): cloudy cornea, conjunctivokeratitis, photophobia, and edema of the muzzle, ears, and vulva. Daily dosing at 2 and 4 g/kg produced (in 72 to 96 hours) similar signs, whereas the smallest dose (1 g/kg) produced mild irritation of the muzzle. Pathologic changes included (1) corneal edema and marked neutrophilic infiltration of the cornea and corneal/ciliary process, (2) subacute ulcerative and exudative dermatitis of the skin of ears, muzzle, and vulva, and (3) mild focal tubular degeneration (vacuolar type) of the kidney. PMID:564651

Witzel, D A; Dollahite, J W; Jones, L P

1978-02-01

242

Pseudomonas asturiensis sp. nov., isolated from soybean and weeds.  

PubMed

Five strains of gram negative bacteria, isolated from soybean (LPPA 221(T), 222 and 223) and weeds (LPPA 816 and 1442), were analyzed by a polyphasic approach. The isolates showed variation in their phenotypic traits and were placed in the Pseudomonas fluorescens lineage, based on 16S rRNA gene sequence phylogeny, as a single but well separated cluster. MLSA analysis based on gyrB and rpoD sequences clustered the strains in a single branch in the Pseudomonas syringae group, and revealed P. viridiflava as closest relative. DNA-DNA hybridizations showed medium levels of DNA-DNA relatedness with the type strain of P. viridiflava (50%) and lower levels (<32%) with other type strains of the P. syringae group, supporting classification within a novel species of the genus Pseudomonas. The strains can be distinguished from species of the P. syringae group by the fatty acid C17:0 cyclo that is present in a low amount (2.5%) and from P. viridiflava by their inability to assimilate d-tartrate and d-sorbitol, and by the formation of red colonies on TTC medium. For this new species, the name Pseudomonas asturiensis sp. nov. is proposed. The type strain is LPPA 221(T) (=LMG 26898(T)=CECT 8095(T)). PMID:23727430

González, Ana J; Cleenwerck, Ilse; De Vos, Paul; Fernández-Sanz, Ana M

2013-07-01

243

Aeropollen of weeds of the western United States Gulf Coast.  

PubMed

Volumetric air sampling was performed near Corpus Christi, Texas during all of 1988. The most significant weeds releasing airborne pollen, besides the Asteraceae, were the Amaranthaceae and Chenopodiaceae at 14.8% of total pollen captured, which peaked in September and October. Greater pollen capture (74%) occurred from a peak at 11 PM at a time when inversions are frequent to 9 AM than during the period from late morning to 9 PM. Frequency of amaranth-chenopod pollen capture in the western Gulf Coast region showed no relationship with frequencies along the northern and eastern Gulf Coast nor in eastern North America generally, but rather with western North America where these grains have also been sampled at high levels. As in the West, therefore, amaranth-chenopod aeropollen is sufficiently frequent to be a major source of allergens in the western Gulf Coast region. Other weedy plants, Cannabis/Humulus, Rumex, and the Urticaceae (Parieteria/Urtica) each account for only about 1% of the total annual pollen shed, and consequently they are not nearly as potentially relevant here in pollinosis as are the amaranth-chenopods and Asteraceae. Plantago pollen is very infrequently sampled (less than 0.1%) even though several species are common in the area. Acalypha is newly reported as releasing airborne pollen, a genus related to Mercurialis known to release allergenic pollen in Europe. PMID:1859040

Lewis, W H; Dixit, A B; Wedner, H J

1991-07-01

244

Transcriptome profiling of the crofton weed gall fly Procecidochares utilis.  

PubMed

Procecidochares utilis is a tephritid gall fly, which is known to be an effective biological agent that can be used to control the notoriously widespread crofton weed Eupatorium adenophorum. Despite its importance, genetic resources for P. utilis remain scarce. In this study, 1.2 Gb sequences were generated using Illumina paired-end sequencing technology. De novo assemblies yielded 491,760 contigs, 90,474 scaffolds, and 58,562 unigenes. Among the unigenes, 34,809 (59.44%) had a homologous match against the National Center for Biotechnology Information non-redundant protein database by translated Basic Local Alignment Search Tool (BlastX) with a cut-off E-value of 10(-5). Among the unigenes, 57,627 were classified in the Gene Ontology database, 15,910 were assigned to Clusters of Orthologous Groups, and 38,565 were found in Kyoto Encyclopedia of Genes and Genomes. In addition, 5723 simple sequence repeats (SSRs) were discovered based on the unigene sequences. The transcriptome sequences and SSRs obtained represent a major molecular resource for P. utilis, which will extend our knowledge of the comparative and functional genomics of this organism and enable population genomic and gene-based association studies of the gall fly. PMID:24682983

Gao, X; Zhu, J Y; Ma, S; Zhang, Z; Xiao, C; Li, Q; Li, Z Y; Wu, G X

2014-01-01

245

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

PubMed

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. PMID:18161884

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

2008-04-01

246

Weed control in conventional and transgenic maize with resistance to glyphosate.  

PubMed

The researches were conducted in order to observe the behaviour of conventional and glyphosate resistant transgenic maize to different weed control methods. In this paper, the obtained results are presented. The study was conducted in experimental years 2008-2009 in the frame of Didactical Station USAMVB Timisoara. In order to conduct this study, 4 variants cultivated with conventional maize DKC 5143 and 8 variants cultivated with transgenic maize DKC-MON88017 with resistance against Diabrotica virgifera virgifera and to glyphosate. The efficacy of weed control methods was assessed, as well as the herbicide selectivity to cultivated maize hybrid. The weed coverage degree in control plot (V2) was 304 weeds/sqm in the first year and 465 weeds/sqm in the second year. In the variants cultivated with transgenic maize the control was up to 90% much more than control percent achieved in conventional variants. Although, in order to achieve an efficient control (higher than 95%), even to transgenic maize, two glyphosate sequential treatments has to be done. The yield results were positive correlated to the different control methods. However those were affected by climatic conditions recorded in experimental years. PMID:21542472

Manea, D; Stef, R; Grozea, I; Carabet, A; Piloca, L

2010-01-01

247

The effects of cover crop on weed control in collard (Brassica olerecea var acephala) and lettuce (Lactuca sativa L.).  

PubMed

Leafy vegetables are not very competitive and weed interference can cause considerable yield losses in collard (Brassica olerecea var acephala) and lettuce (Lactuca sativa L.). Currently there are no pre or post emergence herbicides registered for weed control in these vegetables in Turkey. For this reason, alternative weed control strategies need to be developed. Cover crop residue could represent an alternative method of weed management in these crops. Field studies were conducted in 2004 at the Black Sea Agricultural Research Institute experimental field in Samsun, Turkey. The cover crop treatments consisted of Sorghum bicolor (L.) Moench, Sorghum vulgare Pers., Vicia villosa L., Amaranthus cruentus L., Pisum sativum L. and the bare ground with no cover crop. All cover crops were seeded by hand and incorporated into the soil on 11 May, 2004. Each plot was 10 m2 (2 x 5 m) and arranged in a randomized complete block design with four replications. All cover crops were incorporated into the soil by discing on 1 September 2004 at flowering stage of the cover crops. Broadleaved weed species were dominant in the experimental area. Most cover crops established well and S. bicolor biomass was the highest. The number of weed species emerging in all treatments was different at 14 DAD (days after desiccation). Similar results were observed at 28 and 56 DAD. Treatments with Vicia villosa residues had fewer weed species and lower total weed densities than other treatments. PMID:17390812

Mennan, H; Ngouajio, M; Isik, D; Kose, B; Kaya, E

2006-01-01

248

Impact of Fall-Seeded Cover Crops and Cover Crop Termination Method on Weed Biomass in the Ensuing Crop  

Microsoft Academic Search

SUMMARY The inclusion of cover crops in a rotation can have several potential benefits, one of which is weed suppression in the following crop. Rye, and to a lesser extent wheat and hairy vetch, tissues are known to contain compounds which may inhibit the germination of small-seeded weeds when released into the soil during residue decomposition. Method of cover crop

Jeff J. Gunderson; Patrick M. Carr; Timothy Winch; Glenn B. Martin

249

Evaluation of the Upland Weed Control Potentiality of Green Tea Waste - Rice Bran Compost and Its Effect on Spinach Growth  

Microsoft Academic Search

This study evaluated the upland weed control potentiality, germination inhibition ability and growth suppression efficiency of the five combinations of green tea waste - rice bran compost (GRC). GRC was prepared by mixing green tea waste and rice bran at five ratios, and allowed to decompose for 5 mo. Application of GRC suppressed weed growth up to 93.4% in number

M. A. I. Khan; K. Ueno; S. Horimoto; F. Komai; K. Tanaka; Y. Ono

250

Yield components and quality of rice in response to graminaceous weed density and rice stink bug populations  

Microsoft Academic Search

Field experiments were conducted in 2002 and 2003 to investigate weed density, its relationship to rice stink bug (Oebalus pugnax, F.) populations, and damage to rice caused by stink bugs. Graminaceous weeds examined were barnyardgrass, Echinochloa crus-galli Beauv., Amazon sprangletop, Leptochloa panicoides (Presl.) Hitchc., broadleaf signalgrass, Brachiaria platyphylla Nash., and large crabgrass, Digitaria sanguinalis, (L.). Rice seed weight, percent filled

K. V. Tindall; B. J. Williams; M. J. Stout; J. P. Geaghan; B. R. Leonard; E. P. Webster

2005-01-01

251

Weed Control in Field Corn ( Zea mays ) with RPA 201772 Combinations with Atrazine and S-Metolachlor 1  

Microsoft Academic Search

The premix atrazine 1 S-metolachlor is commonly used to control a wide range of weeds in corn, but it is weak on velvetleaf and several other broadleaf species. RPA 201772, used at reduced rates in combination with atrazine 1 S-metolachlor, may improve the weed control spectrum. In field studies at Urbana and Dekalb in 1998 and 1999, RPA 201772 was

SARAH TAYLOR-LOVELL; LOYD M. WAX

2001-01-01

252

Clover as a cover crop for weed suppression in an intercropping design. I. Characteristics of several clover species  

Microsoft Academic Search

Weeds often form a major problem in weakly competitive vegetable crops, particularly in low input systems. Undersown cover crops can be used to suppress weeds, but often put too high a competitive pressure on the main crop. Cover crop selection is one of the potential means that can be used to design or optimize these intercropping systems. The objective of

Hollander den N. G; L. Bastiaans; M. J. Kropff

2007-01-01

253

Weed management in dry beans ( Phaseolus vulgaris) with dimethenamid plus reduced doses of imazethapyr applied preplant incorporated  

Microsoft Academic Search

Three field trials were conducted over a 3-year period (2003, 2004 and 2005) near Exeter, Ontario to determine if dimethenamid tank-mixed with reduced doses of imazathapyr applied preplant incorporated (PPI) can be used as an efficacious, environmentally acceptable, and economically feasible weed management strategy for broad spectrum weed control in white and kidney beans. There was no additional injury in

Nader Soltani; Laura L. Van Eerd; Richard Vyn; Christy Shropshire; Peter H. Sikkema

2007-01-01

254

Weed flora in the early growth period of spring crops under conventional, reduced, and zero tillage systems on a clay soil in northern Alberta, Canada  

Microsoft Academic Search

An understanding of tillage effects on frequency, density and species composition of the weed population could be used to improve weed management systems. This study was conducted from 1989 to 1993, to evaluate the effects of three primary tillage systems on the weed population during the early growth period of spring crops, i.e. barley (Hordeum vulgare L.), canola (Brassica campestris

K. S. Gill; M. A. Arshad

1995-01-01

255

Utilizing hyperspectral and multispectral remote sensing and geographic information systems to identify and differentiate weed and crop species  

NASA Astrophysics Data System (ADS)

Weed species are not evenly distributed across a field; thus, if remote sensing imagery could be utilized as a tool for locating and identifying these patches, herbicides could be applied according to species and spatial distribution. In order to utilize site-specific technology to apply herbicides, the spatial variability of weed populations within a field must be known. Research was conducted to determine if remote sensing could be utilized as a tool for identifying and separating weed species from cotton and corn. Additionally geographic information systems and herbicide decision aids were tested to determine if weed population mapping could result in accurate site-specific and multiple product herbicide applications. Species separation based on hyperspectral data was successful in differentiating cotton and corn from weed species. By identifying the best spectral bands and utilizing vegetation indices, species classification ranged from 67 to 99% for cotton, 47 to 98% for corn and 95 to 98% for weed species. Species identification increased with data accumulation later in the growing season due to increased leaf area and biomass. Results indicate that weed and crop separation is possible when the best spectral bands are identified and utilized in conjunction with vegetation indices. Multispectral imagery was also tested for species identification and was found to produce lower classification accuracies than hyperspectral data. Cotton and corn were classified 50 to 100%; however, weed species classification was poor (<50%) with multispectral imagery. Poor classification was observed because only 4 regions of the electromagnetic spectrum were utilized. Multispectral identification would likely improve if the best spectral bands identified in the hyperspectral research were utilized in sensors for aerial imagery. Weed species and density information was mapped utilizing a geographic information system. Site-specific and broadcast herbicide applications were made based on results from the herbicide application decision support system (HADSS) program. Weed efficacy or cotton yield did not differ between site-specific or broadcast applications. However, herbicide product, along with associated costs, was reduced with site-specific applications. Overall results from this research provide new technological advances in weed and crop identification as well as controlling weed patches with state of the art site-specific, point-injection technology. The identification of the best spectral bands for weed and crop separation and utilization of the point-injection site-specific sprayer may revolutionize future weed control practices.

Barber, Lon Thomas

256

New crop/weed/soil discrimination uses only one wavelength to reproduce the near-infrared signature  

NASA Astrophysics Data System (ADS)

Plant species discrimination by optical reflectance requires us to analyze reflectance spectral differences between two sampled broad band signatures making use of the discriminative integration index, DII. Crop/weed discrimination analyses of these indexes using a crop threshold introduces the discrimination efficiency of the entire vegetation population consisting of crop and weeds. Best discriminative efficiencies are spectral dependant and results for leek, cabbage, turnip and potato crops having competence with ten different weed species are presented. With the reflectance of an unique wavelength found iteratively, it was possible to reproduce the NIR spectrum of the crop or weed. This reflectance was multiplied by the crop reference spectrum, producing a pattern similar to the real crop signature and for the four crops tested the control wavelength corresponded to the one having the peak reflectance at the red region. This algorithm is the heart of a new model used to distinguish crops from weeds and the results achieved per group are presented.

Hahn, Federico

1996-11-01

257

Evolved glyphosate-resistant weeds around the world: lessons to be learnt.  

PubMed

Glyphosate is the world's most important herbicide, with many uses that deliver effective and sustained control of a wide spectrum of unwanted (weedy) plant species. Until recently there were relatively few reports of weedy plant species evolving resistance to glyphosate. Since 1996, the advent and subsequent high adoption of transgenic glyphosate-resistant crops in the Americas has meant unprecedented and often exclusive use of glyphosate for weed control over very large areas. Consequently, in regions of the USA where transgenic glyphosate-resistant crops dominate, there are now evolved glyphosate-resistant populations of the economically damaging weed species Ambrosia artemissifolia L., Ambrosia trifida L., Amaranthus palmeri S Watson, Amaranthus rudis JD Sauer, Amaranthus tuberculatus (Moq) JD Sauer and various Conyza and Lolium spp. Likewise, in areas of transgenic glyphosate-resistant crops in Argentina and Brazil, there are now evolved glyphosate-resistant populations of Sorghum halepense (L.) Pers and Euphorbia heterophylla L. respectively. As transgenic glyphosate-resistant crops will remain very popular with producers, it is anticipated that glyphosate-resistant biotypes of other prominent weed species will evolve over the next few years. Therefore, evolved glyphosate-resistant weeds are a major risk for the continued success of glyphosate and transgenic glyphosate-resistant crops. However, glyphosate-resistant weeds are not yet a problem in many parts of the world, and lessons can be learnt and actions taken to achieve glyphosate sustainability. A major lesson is that maintenance of diversity in weed management systems is crucial for glyphosate to be sustainable. Glyphosate is essential for present and future world food production, and action to secure its sustainability for future generations is a global imperative. PMID:18273881

Powles, Stephen B

2008-04-01

258

Monitoring aquatic weeds in a river system using SPOT 5 satellite imagery  

NASA Astrophysics Data System (ADS)

Aquatic weeds have caused significant problems in many lakes and river systems worldwide. Weed outbreaks of water hyacinth (Eichhornia crassipes) and para-grass (Urochloa mutica) are common in Australia and their ecological and recreational impacts mostly negative and costly. Remote sensing offers the ability to map and monitor the distribution of aquatic weeds and their early detection. The objective of this project was to develop an efficient method, using remote sensing techniques, to map and monitor the change of dense water weeds in a river system and to identify a suitable spatial scale for this process. Two SPOT (Satellite Pour l'Observation de la Terre) 5 images from May 2006 and May 2007 were used in combination with two mapping approaches on a) multispectral image data with 10 m spatial resolution and b) pan-sharpened multispectral image data with 2.5 m spatial resolution. A scale dependent validation resulted in case b) an overall producer's classification accuracy of 81%. Small outbreaks (~2 m2) alone were 71% accurate with increasing accuracies of >95% for outbreaks larger than 6.25m2 (2.5m x 2.5m pixel). Case a) generally had lower accuracies, with accuracies of >95% for outbreaks in the order of 100m2 (10m x 10m pixel) and larger. The results suggest that the river infestation by aquatic weeds in a test area of the mid-Brisbane River has increased by a factor of 2 to 3 during the 12-month period. The infested area is estimated to be between 13.6% and 15.9 % of the waterbody in 2007, while 6.2% to 6.8% in 2006. The method applied in this study included geometric and radiometric corrections, along with linear spectral unmixing and spectral angle mapper techniques. This method is applicable to other waterways worldwide and offers the potential for the early detection of infestations of aquatic surface weeds.

Schmidt, Michael; Witte, Christian

2010-04-01

259

Susceptibility of Several Common Subtropical Weeds to Meloidogyne arenaria, M. incognita, and M. javanica  

PubMed Central

Experiments were conducted in the greenhouse to assess root galling and egg production of three root-knot nematode species, Meloidogyne arenaria, M. incognita, and M. javanica, on several weeds common to Florida agricultural land. Weeds evaluated were Amaranthus retroflexus (redroot pigweed), Cyperus esculentus (yellow nutsedge), Eleusine indica (goosegrass), Portulaca oleracea (common purslane), and Solanum americanum (American black nightshade). Additionally, although it is recommended as a cover crop in southern regions of the U.S., Aeschynomene americana (American jointvetch) was evaluated as a weed following the detection of root galling in a heavy volunteer infestation of an experimental field in southeastern Florida. Weeds were propagated from seed and inoculated with 1000 nematode eggs when plants reached the two true-leaf stage. Tomato (Solanum lycopersicum ‘Rutgers’) was included as a positive control. Aeschynomene americana and P. oleracea roots supported the highest number of juveniles (J2) and had the highest number of eggs/g of root for all three species of Meloidogyne tested. However, though P. oleracea supported very high root levels of the three nematode species tested, its fleshy roots did not exhibit severe gall symptoms. Low levels of apparent galling, combined with high egg production, increase the potential for P. oleracea to support populations of these three species of root-knot nematodes to a degree that may not be appropriately recognized. This research quantifies the impact of P. oleracea as a host for M. arenaria, M. incognita, and M. javanica compared to several other important weeds commonly found in Florida agricultural production, and the potential for A. americana to serve as an important weed host of the three species of root-knot nematode tested in southern regions of Florida.

Kokalis-Burelle, Nancy; Rosskopf, Erin N.

2012-01-01

260

Responsiveness of arthropod herbivores and their natural enemies to modified weed management in corn.  

PubMed

Alteration of weed flora as consequence of the deployment of genetically modified herbicide-tolerant crops may affect higher trophic levels in agrosystems. A 4-yr study is being conducted in Spain to investigate interrelations between weeds and associated arthropods in corn fields. In a first step, the work aimed to detect the most responsive arthropods to weed management changes. To identify the most responsive arthropods, arthropod composition and abundance in herbicide-tolerant corn plots treated twice with glyphosate and untreated plots were compared for 2 yr. Plots were sampled seven times during the season by visual inspection and pitfall and yellow sticky traps to estimate abundance and activity of the main arthropod herbivores, predators, and parasitoids. As intended, the abundance and composition of weed flora was strongly altered by the differential herbicide treatments. Several groups of arthropods responded to the weed changes but in variable directions. Whereas leafhoppers and aphids were more abundant on herbicide-treated plots, the contrary was found for phytophagous thrips. Among predators, Orius sp., spiders, and trombidids were more abundant on treated plots, whereas nabids and carabids were more abundant in untreated plots; the same case was found for carabids and spiders caught in pitfall traps. Among parasitoids, ichneumonids were more abundant in untreated plots and mymarids in treated plots. These results cannot be interpreted in terms of nontarget effects of postemergence treatments with broad-spectrum herbicides; for this, a comparison with conventional weed management practices should be done and this is the current step in the study. PMID:19508806

Albajes, Ramon; Lumbierres, Belén; Pons, Xavier

2009-06-01

261

Susceptibility of Several Common Subtropical Weeds to Meloidogyne arenaria, M. incognita, and M. javanica.  

PubMed

Experiments were conducted in the greenhouse to assess root galling and egg production of three root-knot nematode species, Meloidogyne arenaria, M. incognita, and M. javanica, on several weeds common to Florida agricultural land. Weeds evaluated were Amaranthus retroflexus (redroot pigweed), Cyperus esculentus (yellow nutsedge), Eleusine indica (goosegrass), Portulaca oleracea (common purslane), and Solanum americanum (American black nightshade). Additionally, although it is recommended as a cover crop in southern regions of the U.S., Aeschynomene americana (American jointvetch) was evaluated as a weed following the detection of root galling in a heavy volunteer infestation of an experimental field in southeastern Florida. Weeds were propagated from seed and inoculated with 1000 nematode eggs when plants reached the two true-leaf stage. Tomato (Solanum lycopersicum 'Rutgers') was included as a positive control. Aeschynomene americana and P. oleracea roots supported the highest number of juveniles (J2) and had the highest number of eggs/g of root for all three species of Meloidogyne tested. However, though P. oleracea supported very high root levels of the three nematode species tested, its fleshy roots did not exhibit severe gall symptoms. Low levels of apparent galling, combined with high egg production, increase the potential for P. oleracea to support populations of these three species of root-knot nematodes to a degree that may not be appropriately recognized. This research quantifies the impact of P. oleracea as a host for M. arenaria, M. incognita, and M. javanica compared to several other important weeds commonly found in Florida agricultural production, and the potential for A. americana to serve as an important weed host of the three species of root-knot nematode tested in southern regions of Florida. PMID:23482324

Kokalis-Burelle, Nancy; Rosskopf, Erin N

2012-06-01

262

Influence of weeds on Argentine ant (Hymenoptera: Formicidae) and obscure mealybug (Hemiptera: Pseudococcidae) in a central California vineyard.  

PubMed

Obscure mealybug is a pest of grapes in the cool climate regions of coastal California, is found on some vineyard weeds, and is tended by the Argentine ant. A study was conducted at a vineyard in Arroyo Grande, CA, to evaluate the impact of weeds on ant activity on grapevines, and the role that ants and weeds have on obscure mealybug infestation in grape clusters. The incidence of the fungus Botrytis cinerea was recorded as well. Treatments were weed exclusion versus the presence of weeds, and ant exclusion versus the presence of ants. Ant activity was evaluated weekly using sugar-based monitoring stations, and mealybug infestation and Botrytis incidence of clusters were evaluated at harvest. Ant exclusion reduced the overall number of ant visits by 82%, and ants increased mealybug infestation of clusters by 53%. Ant activity was 33% higher in the weeds treatment, but there was no impact of weeds on mealybug infestation. We suggest that the higher ant activity recorded in the weeds treatment may have been an artifact of the sugar-based sampling method. Botrytis incidence was three times higher with ants, but did not differ between weeds and weed exclusion treatments. The study supports other research showing a relationship between mealybug infestation and the presence of ants, as well as the lack of impact of floor vegetation on mealybug infestation of grape clusters. It is the first report of a relationship between ants and Botrytis, although it is more likely that the higher Botrytis incidence found here is a result of increased mealybug density than a direct effect by ants. PMID:25026682

Costello, Michael J; Welch, Mark D

2014-06-01

263

Water hyacinths and alligator weeds for removal of silver, cobalt, and strontium from polluted waters  

NASA Technical Reports Server (NTRS)

Water hyacinths and alligator weeds demonstrated the ability to rapidly remove heavy metals from an aqueous system by root absorption and concentration. Water hyacinths demonstrated the ability to remove 0.439 mg of silver, 0.568 mg of cobalt, and 0.544 mg of strontium in an ionized form per gram of dry plant material in a 24-hour period. Alligator weeds removed a maximum of 0.439 mg of silver, 0.130 mg of cobalt, and 0.161 mg of strontium per gram of dry plant material per day.

Wolverton, B. C.; Mcdonald, R. C.

1975-01-01

264

What's in a Name? Can Mullein Weed Beat TB Where Modern Drugs Are Failing?  

PubMed Central

Common mullein weed (Verbascum thapsus) has a large number of synonyms and old local “nick names” which connect the plant with mycobacteria. A strong history of medicinal use has been uncovered for the treatment of tuberculosis, tubercular skin disease, leprosy, and mycobacterial disease in animals. Here, we examine problems encountered in treating such diseases today, the historical and scientific links between mullein and pathogenic bacteria, and the possibility that this common weed could harbour the answer to beating one of the world's biggest infectious killers.

McCarthy, Eibhlin; O'Mahony, Jim M.

2011-01-01

265

Studies on activity recovery in some mercury-exposed freshwater fish by using selected weeds  

SciTech Connect

In spite of worldwide concern about mercury contamination in aquatic environment, relatively little effort has been expended on determining the mechanisms involved in bioaccumulation. It has been found that several species of aquatic plants grow in flowing water of polluted rivers and contain higher mercury levels than the associated water phase. The aquatic weed plants absorb and incorporate the dissolved materials (both inorganic and organic compound) into their own body tissues to rapidly and effectively that they are now considered for use in sewage treatment. The present study evaluated the relative efficiencies of five selected weeds, in mercury toxicity removal suggesting possible methods of mercury removal from contaminated aquatic environments.

Shrivastave, S.; Rao, K.S. (Vikram Univ., Ujjain (India))

1989-06-01

266

Characterization of mutagenic principles and carcinogenicity of dill weed and seeds.  

PubMed

Among the various kinds of spices tested, the aqueous extracts of dill weed from Anethum graveolens L. and dill seeds from A. sowa D.C. (Umbelliferae), exhibited a mutagenicity to Salmonella typhimurium, strains TA98 and TA100. The aqueous methanol extracts were fractionated by the mutation assay using the strain TA98 with S-9 Mix. Isorhamnetin 3-sulfate (persicarin) and quercetin 3-sulfate were characterized as the mutagenic principles. Carcinogenicity was not observed for dill weed and seeds when the diets containing these in 33% were administered for 450 and 410 days, respectively, to the inbred strain ACI rats. PMID:7411385

Fukuoka, M; Yoshihira, K; Natori, S; Sakamoto, K; Iwahara, S; Hosaka, S; Hirono, I

1980-05-01

267

Integrated Weed Control for Land Stewardship at Legacy Management's Rocky Flats Site in Colorado - 13086  

SciTech Connect

Land stewardship is one of nine sustainability programs in the U.S. Department of Energy's Environmental Management System. Land stewardship includes maintaining and improving ecosystem health. At the Rocky Flats Site near Westminster, Colorado, land stewardship is an integral component of the Office of Legacy Management's post-closure monitoring and management at the site. Nearly 263 hectares (650 acres) were disturbed and re-vegetated during site cleanup and closure operations. Proactive management of revegetation areas is critical to the successful reestablishment of native grasslands, wetlands, and riparian communities. The undisturbed native plant communities that occur at the site also require active management to maintain the high-quality wetlands and other habitats that are home to numerous species of birds and other wildlife such as elk and deer, rare plant communities, and the federally listed threatened Preble's meadow jumping mouse. Over the past several decades, an increase of Noxious weeds has impacted much of Colorado's Front Range. As a result, weed control is a key component of the land stewardship program at Rocky Flats. Thirty-three species of state-listed Noxious weeds are known to occur in the Central and Peripheral Operable Units at Rocky Flats, along with another five species that are considered invasive at the site. Early detection and rapid response to control new invasive species is crucial to the program. An integrated weed control/vegetation management approach is key to maintaining healthy, sustainable plant communities that are able to resist Noxious weed invasions. Weed mapping, field surveys, and field-staff training sessions (to learn how to identify new potential problem species) are conducted to help detect and prevent new weed problems. The integrated approach at Rocky Flats includes administrative and cultural techniques (prevention), mechanical controls, biological controls, and chemical controls. Several species of biocontrol insects have been released to assist with control of different target weed species. Monitoring is conducted to evaluate the effectiveness of control efforts and to provide information for future control efforts. The effective implementation of this integrated approach has reduced the infestation levels of many species and has kept several newly discovered invasive species from spreading and becoming larger problems at the site. (authors)

Nelson, Jody K. [Stoller LMS Team, Contractor to the U.S. Department of Energy Office of Legacy Management, 11025 Dover Street, Suite 1000, Westminster, Colorado 80021 (United States)] [Stoller LMS Team, Contractor to the U.S. Department of Energy Office of Legacy Management, 11025 Dover Street, Suite 1000, Westminster, Colorado 80021 (United States)

2013-07-01

268

Allelopathic effects of Medicago sativa L. and Vicia cracca L. leaf and root extracts on weeds.  

PubMed

In this study, the allelopathic potential of different concentration (5, 25 and 50%) of M. sativa and V. cracca leaf and root extracts were evaluated on germination and radicle length of four weed species (Amaranthus retroflexus L., Lolium perenne L., Ipomoea hederacea L. and Portulaca oleracea L.) in laboratory condition. As a result, germination and radicle length of all species were reduced by the extract from M. sativa and V. cracca leaf and root at different percentage. Increasing the water extract concentrations from 5 to 50% of test plants parts significantly increased the inhibition of all weed species germination and radicle length. PMID:19086510

Koloren, Onur

2007-05-15

269

Applying neural networks to hyperspectral and multispectral field data for discrimination of cruciferous weeds in winter crops.  

PubMed

In the context of detection of weeds in crops for site-specific weed control, on-ground spectral reflectance measurements are the first step to determine the potential of remote spectral data to classify weeds and crops. Field studies were conducted for four years at different locations in Spain. We aimed to distinguish cruciferous weeds in wheat and broad bean crops, using hyperspectral and multispectral readings in the visible and near-infrared spectrum. To identify differences in reflectance between cruciferous weeds, we applied three classification methods: stepwise discriminant (STEPDISC) analysis and two neural networks, specifically, multilayer perceptron (MLP) and radial basis function (RBF). Hyperspectral and multispectral signatures of cruciferous weeds, and wheat and broad bean crops can be classified using STEPDISC analysis, and MLP and RBF neural networks with different success, being the MLP model the most accurate with 100%, or higher than 98.1%, of classification performance for all the years. Classification accuracy from hyperspectral signatures was similar to that from multispectral and spectral indices, suggesting that little advantage would be obtained by using more expensive airborne hyperspectral imagery. Therefore, for next investigations, we recommend using multispectral remote imagery to explore whether they can potentially discriminate these weeds and crops. PMID:22629171

de Castro, Ana-Isabel; Jurado-Expósito, Montserrat; Gómez-Casero, María-Teresa; López-Granados, Francisca

2012-01-01

270

Morphology and yield response to weed pressure by corn hybrids differing in canopy architecture  

Microsoft Academic Search

Recently, corn (Zea mays L.) hybrids accumulating more leaf area above the ear, maturing earlier, yielding better in narrower row spacings and tolerating higher population densities than conventional hybrids have been developed. However, no research has been conducted to assess their ability to compete with weeds. The objective of this study was to quantify morphological and grain yield responses of

S. H. Begna; R. I. Hamilton; L. M. Dwyer; D. W. Stewart; D. Cloutier; L. Assemat; K. Foroutan-pour; D. L. Smith

2001-01-01

271

On the Adequacy of GIS-Generated Weed Maps for Precision Farming  

Microsoft Academic Search

Discrete sampling data is used in several environmental studies to create maps in order to support decision-making processes. The decision maps represent an increasing importance in modern Precision Farming. For the application of herbicides in a field, maps of weed distribution are necessary. The uncertainty of those, resulting from sparse sampling patterns is one major reason why farmers tend to

Matthias Backes; Lutz Plümer

2003-01-01

272

Use of random amplified polymorphic DNA (RAPD) markers in the study of the parasitic weed Orobanche  

Microsoft Academic Search

Despite the tremendous economic impact of broomrapes (Orobanche spp.) on agriculture in many countries little is known of the pattern of genetic variation within this group of parasitic weeds. The present paper describes the use of RAPD markers for the study of five Orobanche species in agricultural fields in Israel. Pronounced genetic differentiation was found between the species, and RAPD

N. Katzir; V. Portnoy; G. Tzuri; D. M. Joel; M. Castejón-Muñoz

1996-01-01

273

Adsorption of Methylene Blue Dye on Pure and Carbonized Water Weeds  

Microsoft Academic Search

The influence of process variables in batch adsorption has been used to assess the removal of methylene blue dye from aqueous solution using pure and carbonized biomasses of water hyacinth and water spinach. Dried leaves of the water weeds were carbonized at temperature up to 750°C. The optimum removal of dye was achieved at pH 10, 30°C, and 55 min

Timi Tarawou; Michael Horsfall Jr

2007-01-01

274

How do floating aquatic weeds affect wetland conservation and development? How can these effects be minimised?  

Microsoft Academic Search

The most important floating aquatic weeds (FAWs) are Eichhornia crassipes, Salvinia molesta and Pistia stratiotes. E. crassipes and P. stratiotes reproduce sexually. All three species reproduce asexually. E. crassipes and S. molesta have particularly high growth rates. All can form dense mats and growth rates are increased by high nutrient levels and temperatures. Spread between continents and watersheds is largely

G. W. Howard; K. L. S. Harley

1997-01-01

275

National Process Evaluation of Operation Weed and Seed. Research in Brief.  

National Technical Information Service (NTIS)

The U.S. Department of Justice launched Operation Weed and Seed in 1991 to demonstrate that a large array of resources can be mobilized in a comprehensive, coordinated effort to control crime and drugs and to improve the quality of life in targeted high-c...

J. A. Roehl R. Huitt M. A. Wycoff A. Pate D. Rebovich K. Coyle

1996-01-01

276

A Handbook of Pests, Diseases, and Weeds of Quarantine Significance. Second Edition.  

National Technical Information Service (NTIS)

The recent increase in imported agricultural products, seeds and plants has augmented the danger of introducing plant pests, diseases, and weeds not otherwise found in the USSR or confined to small areas. This threat places a grave responsibility on the q...

1978-01-01

277

Modelling integrated weed management of an invasive shrub in tropical Australia  

Microsoft Academic Search

Summary 1. Where biocontrol programmes for invasive plants are in place, only one-third are fully successful. Integrated weed management (IWM) emphasizes the use of several complementary control measures. 2. We used models of increasing complexity to determine which parameters affect site occupancy of an invasive shrub, Mimosa pigra , in tropical Australia. Two introduced biocontrol agents have spatial effects on

YVONNE M. BUCKLEY; MARK REES; QUENTIN PAYNTER; MARK LONSDALE

2004-01-01

278

Weed populations and pickling cucumber ( Cucumis sativus) yield under summer and winter cover crop systems  

Microsoft Academic Search

Cucumber growers are increasingly interested in integrating cover crops into their cropping systems. This study was conducted to measure the effect of summer and winter cover crops on weed populations and cucumber yield. The experimental design was a factorial of cover crop and killing method. The cover crops were sorghum sudangrass [Sorghum bicolor (L) x S. sudanense (P) Stapf.], cereal

M. Ngouajio; H. Mennan

2005-01-01

279

Comparative study on chemical pretreatment methods for improving enzymatic digestibility of crofton weed stem.  

PubMed

In order to utilize and control the invasive weed, crofton weed (Eupatorium adenophorum Spreng), a potential pathway was proposed by using it as a feedstock for production of fermentable sugars. Three chemical pretreatment methods were used for improving enzymatic saccharification of the weed stem. Mild H2SO4 pretreatment could obtain a relatively high yield of sugars in the pretreatment (32.89%, based on initial holocellulose), however, it led to only a slight enhancement of enzymatic digestibility. NaOH pretreatment could obtain a higher enzymatic conversion ratio of cellulose compared with H2SO4 pretreatment. Peracetic acid (PAA) pretreatment seemed to be the most effective for improving enzymatic saccharification of the weed stem in the three chemical pretreatment methods under the same conditions. The conversion ratio of cellulose in the sample pretreated by PAA under the "optimal" condition was increased to 50% by cellulase loading of 80 FPU/g cellulose for 72 h incubation. A number of empirical quadratic models were successfully developed according to the experimental data to predict the yield of sugar and degree of delignification. PMID:17709243

Zhao, Xuebing; Zhang, Lihua; Liu, Dehua

2008-06-01

280

Weeding and Seeding: Programming for Alcohol Abuse Prevention and Wellness Enhancement in an Undergraduate Population  

ERIC Educational Resources Information Center

College students who are no longer fully adolescent and not yet fully adult are frequently at risk for developing habits of excessive alcohol use, with consequent poor study habits and aberrant socialization patterns. "Weeding out" such trends is the work of prevention programs on campus. "Seeding" with other pro-social norms becomes the second…

Halligan, Fredrica R.; Pohl, Jonathan A.; Smith, M. Katrina

2006-01-01

281

Strigolactones: Chemical Signals for Fungal Symbionts and Parasitic Weeds in Plant Roots  

PubMed Central

• Aims Arbuscular mycorrhizae are formed between >80 % of land plants and arbuscular mycorrhizal (AM) fungi. This Botanical Briefing highlights the chemical identification of strigolactones as a host-recognition signal for AM fungi, and their role in the establishment of arbuscular mycorrhizae as well as in the seed germination of parasitic weeds. • Scope Hyphal branching has long been described as the first morphological event in host recognition by AM fungi during the pre-infection stages. Host roots release signalling molecules called ‘branching factors’ that induce extensive hyphal branching in AM fungi. Strigolactones exuded from host roots have recently been identified as an inducer of hyphal branching in AM fungi. Strigolactones are a group of sesquiterpenes, previously isolated as seed germination stimulants for the parasitic weeds Striga and Orobanche. Parasitic weeds might find their potential hosts by detecting strigolactones, which are released from plant roots upon phosphate deficiency in communication with AM fungi. In addition to acting as a signalling molecule, strigolactones might stimulate the production of fungal symbiotic signals called ‘Myc factors’ in AM fungi. • Conclusions Isolation and identification of plant symbiotic signals open up new ways for studying the molecular basis of plant–AM-fungus interactions. This discovery provides a clear answer to a long-standing question in parasitic plant biology: what is the natural role for germination stimulants? It could also provide a new strategy for the management and control of beneficial fungal symbionts and of devastating parasitic weeds in agriculture and natural ecosystems.

AKIYAMA, KOHKI; HAYASHI, HIDEO

2006-01-01

282

Allelopathic Effects of Helianthus Tuberosus L. on Germination and Seedling Growth of Several Crops and Weeds  

Microsoft Academic Search

Helianthus tuberosus L. (Jerusalem artichoke) is a perennial herbaceous species which is cultivated for human and animal consumption and sometimes reported as a dangerous weed in several summer crops. Few reports indicate that this species shows allelopathic behaviour. This study, carried out in laboratory and greenhouse conditions, investigated the effects of aqueous extracts from leaf tissues and powdered dried leaves

Francesco Vidotto; Franco Tesio; Aldo Ferrero

2008-01-01

283

Population genetics of the invasive water weed Elodea canadensis in Finnish waterways  

Microsoft Academic Search

Invasions of exotic species often involve a rapid evolutionary change in the introduced populations. Elodea canadensis is an invasive aquatic weed native to North America. Our aims were to reveal the evolutionary consequences of invasion to\\u000a the population genetic structure of the presumably clonal E. canadensis in Finland and to test the hypothesis that the whole Finnish population originates from

T. Huotari; H. Korpelainen; E. Leskinen; K. Kostamo

2011-01-01

284

Weed Control in Strawberry Provided by Shank and Drip-applied Methyl Bromide Alternative Fumigants  

Microsoft Academic Search

The loss of methyl bromide (MB) as a soil fumigant has created the need for new weed management systems for crops such as strawberry (Fragaria ·ananassa Duch- esne). Potential alternative chemicals to replace methyl bromide fu mi ga tion include 1,3-D, chloropicrin (CP), and metam sodium. Application of emulsifi ed formulations of these fumigants through the drip irrigation system is

S. A. Fennimore; M. J. Haar; H. A. Ajwa

285

The Use of Spectral Properties for Weed Detection and Identification - A Review  

Microsoft Academic Search

Many approaches to weed detection and identification have been reported in the literature. Most of these approaches can be categorized as being spatial, based on plant morphology, spectral, based on the light reflected from the plant surfaces, and hybrids of the two. This paper is a review of spectral techniques that have been reported. This includes equipment for data acquisition,

S. D. Noble; R. B. Brown; T. G. Crowe

286

Preliminary Phytochemical Analysis and Antimicrobial Activity of Some Weeds collected from Marathwada Region  

Microsoft Academic Search

The aqueous and ethanolic extracts of selected weeds such as Portulaca oleracea L. (Portulaceae), Cardiospermum helicacabum L. (Sapindaceae), Euphorbia hirta L. (Euphorbiaceae), Crotalaria retusa L. (Fabaceae) and Euphorbia heterophylla L. (Euphorbiaceae) were screened for phytochemical analysis and antimicrobial activity. The antimicrobial activities were tested against two gram-positive bacteria (Bacillus subtilis, Staphylococus aureus), one gram-negative bacterium (Pseudomonas aeruginosa) and a mould

Dhole JA; Dhole NA; Lone KD; Bodke SS; Rajarshi Shahu

2011-01-01

287

WEED FLORA OF PIR MEHR ALI SHAH ARID AGRICULTURE UNIVERSITY RAWALPINDI: WINTER ASPECT  

Microsoft Academic Search

Weeds inventory survey was conducted in the PMAS-Arid Agriculture University, Rawalpindi campus during October, 2007 to February, 2008. Plant specimens were collected, dried, pressed and mounted on sheet and deposited in the Department of Botany, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi. The status of each taxa was determined by taking frequency percentage. During the survey, a total of

Rabia Nazar; Sabila Begum; Azra Naz; Rahmatullah Qureshi; Rabia Asma Memon; Abdul Khaliq Chaudhry; Zahid Akram

288

Foraging behaviour of bee pollinators on the tropical weed Triumfetta semitriloba : departure rules from flower patches  

Microsoft Academic Search

Summary We studied the departure rules from flower patches used by bee pollinators of the tropical shrub weed Triumfetta semitriloba Jacq. (Tiliaceae). Flowering plants were distributed in well delimited clumps, in each of two pasture areas (A1 and A2) and one area of forest gap (A3), in Viçosa, southeastern Brazil. Five solitary bee species, Augochlorella michaelis, Augochloropsis cupreola, Pseudocentron paulistana,

R. G. Collevatti; L. A. O. Campos; J. H. Schoereder

1997-01-01

289

Phytosociological and conservational study of the arable weed communities in western Hungary  

Microsoft Academic Search

The present study surveyed the weed vegetation on extensively managed arable fields and unsprayed field edges in western Hungary, based on 1698 phytosociological relevés collected between 1995 and 2005. The separation of the 15 vegetation units was conducted with the traditional comparative tabular method, and the diagnostic species were determined with statistical fidelity measures. The numerical analyses show that the

Gyula Pinke; Robert Pál

2008-01-01

290

Weed, Yes! Discard, No! There May Be a Collection in that Trash!  

ERIC Educational Resources Information Center

In the course of a weeding project at a small community college library, librarians discovered an unusual nineteenth century literary collection consisting of many obscure titles written by people of color, women and ethnic minorities. Though the materials were not rare, they constituted an interesting and valuable set of materials. These…

McGowan, Beth

2011-01-01

291

Earleaf acacia, a fast growing, brittle exotic weed tree in Florida  

SciTech Connect

A description is given of Acacia auriculiformis, together with a warning against its use for ornamental landscaping in Florida (a hurricane area). The tree grows very fast, reaching 30-55 ft in 8 years, lacks wind resistance, produces much persistent litter, seeds itself freely and is now a common weed species in Florida. The wood is of value for handicrafts. 3 references.

Morton, J.F.

1986-01-01

292

Early establishment of planted Retama sphaerocarpa seedlings under different levels of light, water and weed competition  

Microsoft Academic Search

Large amounts of former cropland are being abandoned in developedregions. To formulate guidelines for land reclamation programmes, we exploredthe effects of artificial shading, irrigation, and removal of weed competitionon the performance of Retama sphaerocarpa (L.) Boiss.seedlings in a factorial experiment located in an abandoned cropland in CentralSpain. R. sphaerocarpa is of interest for revegetationbecause it is a drought tolerant leguminous

José María Rey Benayas; Antonio López-Pintor; Carmen García; Nuria de la Cámara; Reto Strasser; Antonio Gómez Sal

2002-01-01

293

Early establishment of planted Retama sphaerocarpa seedlings under different levels of light, water and weed competition  

Microsoft Academic Search

Large amounts of former cropland are being abandoned in developed regions. To formulate guidelines for land reclamation programmes, we explored the effects of artificial shading, irrigation, and removal of weed competi- tion on the performance of Retama sphaerocarpa (L.) Boiss. seedlings in a factorial experiment located in an abandoned cropland in Central Spain. R. sphaerocarpa is of interest for revegetation

José María Rey Benayas; Antonio López-Pintor; Carmen García; Nuria de la Cámara; Reto Strasser; Antonio Gómez Sal

2002-01-01

294

Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets  

Microsoft Academic Search

This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank.

J-F Arnaud; J Cuguen; S Fénart

2011-01-01

295

EFFECT OF CELERIAC-LEEK INTERCROPPING ON WEEDS, INSECTS AND PLANT GROWTH  

Microsoft Academic Search

Intercropping of field vegetables favours utilization of water, nutrients, cropping area and productivity of cultivated plants. At the same time it can reduce occurrence of weeds, deseares and insects (Baumann et al. 2000, Lamberts 1980, Wiech 1993). These advantegous effects are attributed partially to allelopathic interaction between cultivated plants and other organism living in the field (Oleszek et al. 2001).

296

BOTANICAL BRIEFING Strigolactones: Chemical Signals for Fungal Symbionts and Parasitic Weeds in Plant Roots  

Microsoft Academic Search

Aims Arbuscular mycorrhizae are formed between >80 % of land plants and arbuscular mycorrhizal (AM) fungi. This Botanical Briefing highlights the chemical identification of strigolactones as a host-recognition signal for AM fungi, and their role in the establishment of arbuscular mycorrhizae as well as in the seed germination of parasitic weeds. Scope Hyphal branching has long been described as the

KOHKI A KIYAMA; H IDEO H AYASHI

297

Rhinocyllus conicus - Insights to Improve Predictability and Minimize Risk of Biological Control of Weeds  

Microsoft Academic Search

A review of information on the release of Rhinocyllus conicus to control of Carduus spp. thistles in North America suggests at least 8 lessons for future biological control efforts. These lessons include the need for: 1) better a priori quantification of the occur- rence and ecological effects of the weed; 2) improved incorporation of ecological criteria to supplement the phylogenetic

S. M. LOUDA

298

Impact of an exotic earthworm on seed dispersal of an indigenous US weed  

Microsoft Academic Search

Summary 1. Ambrosia trifida L. (giant ragweed), an aggressive weed of US grain crops and indigenous to North America, colonizes no-tillage crop fields and undisturbed soils despite its large seed size and susceptibility to seed predation. Secondary seed dispersal is critical to seed survival and seedling establishment, yet mechanisms of secondary dispersal are poorly understood for such large-seeded weedy species.

E. Regnier; S. K. Harrison; J. Liu; J. T. Schmoll; C. A. Edwards; N. Arancon; C. Holloman

2008-01-01

299

Population dynamics of weeds in no-tillage and conventional crop systems.  

PubMed

Population dynamics of weeds in successive maize and bean crops were evaluated in two soil management systems (conventional and no-tillage), for two maize applications (grain and silage), and in four consecutive growing seasons. Every year, conventional tillage consisted in plowing and harrowing before sowing. In no-tillage, chemical weed desiccation was made with the mixture glyphosate + 2.4-D. To control weeds, the mixture fluazifop-p-butil + fomesafen was applied on the bean crop in all the planting seasons, and the herbicides nicosulfuron + atrazine on maize after crop emergence (1998--1999, 1999--2000, 2001--2002) and atrazine + metolachlor before emergence (2000--2001). Purple nutsedge (Cyperus rotundus) was the most important species under conventional soil tillage; while in no-tillage the dicotyledonous weed species (Amaranthus deflexus, Bidens pilosa, Euphorbia heterophylla, Galinsoga parviflora Ipomoea grandifolia) were the most relevant. Regardless of the maize use, the C. rotundus population and tuber bank, with prevailingly dormant tubers, was considerably reduced in no-tillage compared with the conventional system. PMID:15656169

Machado, Aroldo Ferreira Lopes; Jakelaitis, Adriano; Ferreira, Lino Roberto; Agnes, Ernani Luiz; Santos, Leonardo David Tuffi

2005-01-01

300

Herbicidal effects of extracts and residue incorporation of Datura metel against parthenium weed  

Microsoft Academic Search

The present study was designed to evaluate the herbicidal activity of Datura metel against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5, 10, 15 and 20% w\\/v (on a fresh weight basis) concentration of D. metel were tested against the germination and seedling growth

Arshad Javaid; Sobiya Shafique; Shazia Shafique

2010-01-01

301

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

PubMed Central

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.

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

2014-01-01

302

The effect of post-emergence weed control on irrigated wheat ( Triticum aestivum L.) in the Sudan savannah of Nigeria  

Microsoft Academic Search

Four post-emergence weed control treatments (piperophos+cinosulfuron, ozadiazon+propanil, 2, 4-D, bentazon+propanil) at various doses were evaluated during the 3 dry seasons of 1999\\/2000, 2000\\/2001 and 2001\\/2002, at Kadawa in the Sudan savannah of Nigeria. These treatments consistently suppressed weed weights compared with the untreated plots. Two hoe weedings or the post-emergence application of 2, 4-D at 1.2kg a.i\\/ha and oxadiazon plus

S. A. Dadari; Hamza Mani

2005-01-01

303

Effect of mechanical weeding on wild chamomile (Matricaria chamomilla L.) populations in winter wheat crop (Triticum aestivum L.).  

PubMed

Currently, economic, agronomic and environmental concerns lead to reduce the use of herbicides. Mechanical weeding can help to reach this objective. Dynamics and biology of wild chamomile (Matricaria chamomilla L.) populations were assessed as well as dynamic of winter wheat (Triticum aestivum L.) for four level of application of a weeder-harrow (0, 1, 2, 3 treatment(s)). After each treatment, an effect of mechanical weeding on wild chamomile density was observed. Density of wild chamomile decreased significantly with intensification of mechanical weeding. A third treatment allowed eliminating late emerged plants. PMID:23878991

Jaunard, D; Bizoux, J P; Monty, A; Henriet, F; De Proft, M; Vancutsem, F; Mahy, G; Bodson, B

2012-01-01

304

Configuration and specifications of an Unmanned Aerial Vehicle (UAV) for early site specific weed management.  

PubMed

A new aerial platform has risen recently for image acquisition, the Unmanned Aerial Vehicle (UAV). This article describes the technical specifications and configuration of a UAV used to capture remote images for early season site- specific weed management (ESSWM). Image spatial and spectral properties required for weed seedling discrimination were also evaluated. Two different sensors, a still visible camera and a six-band multispectral camera, and three flight altitudes (30, 60 and 100 m) were tested over a naturally infested sunflower field. The main phases of the UAV workflow were the following: 1) mission planning, 2) UAV flight and image acquisition, and 3) image pre-processing. Three different aspects were needed to plan the route: flight area, camera specifications and UAV tasks. The pre-processing phase included the correct alignment of the six bands of the multispectral imagery and the orthorectification and mosaicking of the individual images captured in each flight. The image pixel size, area covered by each image and flight timing were very sensitive to flight altitude. At a lower altitude, the UAV captured images of finer spatial resolution, although the number of images needed to cover the whole field may be a limiting factor due to the energy required for a greater flight length and computational requirements for the further mosaicking process. Spectral differences between weeds, crop and bare soil were significant in the vegetation indices studied (Excess Green Index, Normalised Green-Red Difference Index and Normalised Difference Vegetation Index), mainly at a 30 m altitude. However, greater spectral separability was obtained between vegetation and bare soil with the index NDVI. These results suggest that an agreement among spectral and spatial resolutions is needed to optimise the flight mission according to every agronomical objective as affected by the size of the smaller object to be discriminated (weed plants or weed patches). PMID:23483997

Torres-Sánchez, Jorge; López-Granados, Francisca; De Castro, Ana Isabel; Peña-Barragán, José Manuel

2013-01-01

305

Configuration and Specifications of an Unmanned Aerial Vehicle (UAV) for Early Site Specific Weed Management  

PubMed Central

A new aerial platform has risen recently for image acquisition, the Unmanned Aerial Vehicle (UAV). This article describes the technical specifications and configuration of a UAV used to capture remote images for early season site- specific weed management (ESSWM). Image spatial and spectral properties required for weed seedling discrimination were also evaluated. Two different sensors, a still visible camera and a six-band multispectral camera, and three flight altitudes (30, 60 and 100 m) were tested over a naturally infested sunflower field. The main phases of the UAV workflow were the following: 1) mission planning, 2) UAV flight and image acquisition, and 3) image pre-processing. Three different aspects were needed to plan the route: flight area, camera specifications and UAV tasks. The pre-processing phase included the correct alignment of the six bands of the multispectral imagery and the orthorectification and mosaicking of the individual images captured in each flight. The image pixel size, area covered by each image and flight timing were very sensitive to flight altitude. At a lower altitude, the UAV captured images of finer spatial resolution, although the number of images needed to cover the whole field may be a limiting factor due to the energy required for a greater flight length and computational requirements for the further mosaicking process. Spectral differences between weeds, crop and bare soil were significant in the vegetation indices studied (Excess Green Index, Normalised Green-Red Difference Index and Normalised Difference Vegetation Index), mainly at a 30 m altitude. However, greater spectral separability was obtained between vegetation and bare soil with the index NDVI. These results suggest that an agreement among spectral and spatial resolutions is needed to optimise the flight mission according to every agronomical objective as affected by the size of the smaller object to be discriminated (weed plants or weed patches).

Torres-Sanchez, Jorge; Lopez-Granados, Francisca; De Castro, Ana Isabel; Pena-Barragan, Jose Manuel

2013-01-01

306

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

PubMed Central

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.

Andujar, Dionisio; Rueda-Ayala, Victor; Moreno, Hugo; Rosell-Polo, Joan Ramon; Escola, Alexandre; Valero, Constantino; Gerhards, Roland; Fernandez-Quintanilla, Cesar; Dorado, Jose; Griepentrog, Hans-Werner

2013-01-01

307

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

PubMed Central

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.

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

2013-01-01

308

What Magnitude Are Observed Non-Target Impacts from Weed Biocontrol?  

PubMed Central

A systematic review focused by plant on non-target impacts from agents deliberately introduced for the biological control of weeds found significant non-target impacts to be rare. The magnitude of direct impact of 43 biocontrol agents on 140 non-target plants was retrospectively categorized using a risk management framework for ecological impacts of invasive species (minimal, minor, moderate, major, massive). The vast majority of agents introduced for classical biological control of weeds (>99% of 512 agents released) have had no known significant adverse effects on non-target plants thus far; major effects suppressing non-target plant populations could be expected to be detectable. Most direct non-target impacts on plants (91.6%) were categorized as minimal or minor in magnitude with no known adverse long-term impact on non-target plant populations, but a few cacti and thistles are affected at moderate (n?=?3), major (n?=?7) to massive (n?=?1) scale. The largest direct impacts are from two agents (Cactoblastis cactorum on native cacti and Rhinocyllus conicus on native thistles), but these introductions would not be permitted today as more balanced attitudes exist to plant biodiversity, driven by both society and the scientific community. Our analysis shows (as far as is known), weed biological control agents have a biosafety track record of >99% of cases avoiding significant non-target impacts on plant populations. Some impacts could have been overlooked, but this seems unlikely to change the basic distribution of very limited adverse effects. Fewer non-target impacts can be expected in future because of improved science and incorporation of wider values. Failure to use biological control represents a significant opportunity cost from the certainty of ongoing adverse impacts from invasive weeds. It is recommended that a simple five-step scale be used to better communicate the risk of consequences from both action (classical biological control) and no action (ongoing impacts from invasive weeds).

Suckling, David Maxwell; Sforza, Rene Francois Henri

2014-01-01

309

Are Weeds Hitchhiking a Ride on Your Car? A Systematic Review of Seed Dispersal on Cars  

PubMed Central

When traveling in cars, we can unintentionally carry and disperse weed seed; but which species, and where are they a problem? To answer these questions, we systematically searched the scientific literature to identify all original research studies that assess seed transported by cars and listed the species with seed on/in cars. From the 13 studies that fit these criteria, we found 626 species from 75 families that have seed that can be dispersed by cars. Of these, 599 are listed as weeds in some part of the world, with 439 listed as invasive or naturalized alien species in one or more European countries, 248 are invasive/noxious weeds in North America, 370 are naturalized alien species in Australia, 167 are alien species in India, 77 are invasive species in China and 23 are declared weeds/invaders in South Africa. One hundred and one are classified as internationally important environmental weeds. Although most (487) were only recorded once, some species such as Chenopodium album, Poa pratensis and Trifolium repens were common among studies. Perennial graminoids seem to be favoured over annual graminoids while annual forbs are favoured over perennial forbs. Species characteristics including seed size and morphology and where the plants grew affected the probability that their seed was transported by cars. Seeds can be found in many different places on cars including under the chassis, front and rear bumpers, wheel wells and rims, front and back mudguards, wheel arches, tyres and on interior floor mats. With increasing numbers of cars and expanding road networks in many regions, these results highlight the importance of cars as a dispersal mechanism, and how it may favour invasions by some species over others. Strategies to reduce the risk of seed dispersal by cars include reducing seed on cars by mowing road verges and cleaning cars.

Ansong, Michael; Pickering, Catherine

2013-01-01

310

Selective weed suppression by cover crop residues: effects of seed mass and timing of species’sensitivity  

Microsoft Academic Search

Laboratory bioassays have shown that large-seeded species better tolerate cover crop residue–mediated stress than small-seeded species. This provides the potential for selective suppression of small-seeded weeds in large-seeded crops. We conducted two field experiments in which seedling emergence of a range of crop and weed species was monitored in soil without cover crop residues and soil with recently incorporated lucerne,

H. M. Kruidhof; E. R. Gallandt; E. R. Haramoto; L. Bastiaans

2011-01-01

311

The Effects of Plant Litter and Inorganic Fertilizer on Crop-Weed Interactions in a Temperate, Rich-Soil Site  

Microsoft Academic Search

Litter (mulch) may have potential for sustaining low-technology agriculture in at least two capacities: as a nutrient source and as weed control. This experiment discriminates between these two possible effects at a temperate site in Michigan, U.S.A. The design consisted of four factors—corn (Zea mays L.), weeds, grass-alfalfa straw mulch, and N-P-K fertilizer—each at two levels, present and absent. Measured

W. Katherine Yih

1989-01-01

312

Allelopathic effect by aqueous extracts of different parts of Croton bonplandianum Baill. on some crop and weed plants  

Microsoft Academic Search

The present study was conducted to investigate the allelopathic effects of Croton bonplandianum weed on seed germination and seedling growth of crop plants (Triticum aestivum L., Brassica oleracea var. botrytis L. and Brassica rapa L.) and weed plants (Melilotus alba Medik., Vicia sativa L. and Medicago hispida Gaertn). Root, stem and leaf aqueous extracts of Croton at 0.5, 1.0, 2.0

Swapnal Sisodia; M. Badruzzaman Siddiqui

313

Evaluation of an autonomous GPS-based system for intra-row weed control by assessing the tilled area  

Microsoft Academic Search

An automatic tillage system for inter- and intra-row weed control based on real-time kinematic GPS navigation and control\\u000a has been used to address the problem of mechanically removing weeds within rows of precision seeded crops. The system comprised\\u000a a side-shifting frame with an attached tine-rotor (cycloid hoe) with eight sigmoid-shaped, vertically directed tines. The\\u000a individual tines can be released for

M. Nørremark; H. W. Griepentrog; J. Nielsen; H. T. Søgaard

314

Fatty acid composition of four potential aquatic weeds and their possible use as fish-feed neutraceuticals  

Microsoft Academic Search

A study was conducted to explore the fatty acid composition of four aquatic weeds, namely Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans collected from water bodies of Assam, India. It has been observed that C24:1 (Cis-15 Tetracosenoic acid) followed by C16:1 n-3 (9-Hexadecenoic acid) are the predominant fatty acids in these aquatic weeds and among them, Ipomoea reptans

A. K. Mukherjee; P. Kalita; B. G. Unni; S. B. Wann; D. Saikia; P. K. Mukhopadhyay

2010-01-01

315

Water hyacinths and alligator weeds for removal of lead and mercury from polluted waters  

NASA Technical Reports Server (NTRS)

Removal of lead and mercury by water hyacinths (Eichhornia crassipes) (Mart.) Solms and alligator weeds (Alternanthera philoxeroides) (Mart.) Griesb. was investigated. Water hyacinths demonstrated the ability to remove 0.176 mg of lead and 0.150 mg of mercury per gram of dry plant material from distilled water and river water in a 24-hour period. One acre of water hyacinths is potentially capable of removing 105.6 grams of lead and 90.0 grams of mercury per day. Alligator weeds removed 0.101 mg of lead per gram of dry plant material in a 24-hour period. This same plant also demonstrated the ability to remove a minimum of 0.153 mg of mercury per gram of dry plant material in a six hour period.

Wolverton, B. C.; Mcdonald, R. C.

1975-01-01

316

An effective means of biofiltration of heavy metal contaminated water bodies using aquatic weed Eichhornia crassipes.  

PubMed

Various aquatic plant species are known to accumulate heavy metals through the process of bioaccumulation. World's most troublesome aquatic weed water hyacinth (Eichhornia crassipes) has been studied for its tendency to bio-accumulate and bio-magnify the heavy metal contaminants present in water bodies. The chemical investigation of plant parts has shown that it accumulates heavy metals like lead (Pb), chromium (Cr), zinc (Zn), manganese (Mn) and copper (Cu) to a large extent. Of all the heavy metals studied Pb, Zn and Mn tend to show greater affinity towards bioaccumulation. The higher concentration of metal in the aquatic weed signifies the biomagnification that lead to filtration of metallic ions from polluted water. The concept that E. crassipes can be used as a natural aquatic treatment system in the uptake of heavy metals is explored. PMID:17072557

Tiwari, Suchi; Dixit, Savita; Verma, Neelam

2007-06-01

317

Bonneville Power Administration, Lower Columbia Region: Noxious Weed Management, 1996 Annual Report.  

SciTech Connect

During the 1996 season ODA executed the contract between BPA and ODA. Execution of this contract included the following activities: Survey for target noxious weeds, such as Gorse; collection and redistribution of biological control agents, for example, Apion seed weevils for Scotch broom, bioagents for diffuse and spotted knapweed, Gorse spider mite, and gall fly releases for control of Canada thistle and bull thistle; and control of isolated infestations of Gorse on BPA rights-of-way. Training was provided for line crews at the Chemawa, Alevy and North Bend districts. The purpose of the program is to assist BPA in the integrated prevention and control of noxious weed species on BPA transmission line maintenance right-of-ways.

United States. Bonneville Power Administration, Portland, OR; Oregon Department of Agriculture Noxious Weed Control Program

1996-01-01

318

Potential utilization of dried powder of Tagetes minuta as a natural herbicide for managing rice weeds  

Microsoft Academic Search

Tagetes minuta is an aromatic essential plant with wide range of biological activity including medicinal properties. A study was undertaken to explore the potential herbicidal activity of Tagetes minuta leaf powder (at 1, 2, and 4tha?1) towards two invasive weeds—Echinochloa crus-galli and Cyperus rotundus—of rice fields. It was observed that T. minuta leaf powder applied to rice field soil significantly

Daizy R. Batish; Komal Arora; Harminder P. Singh; Ravinder K. Kohli

2007-01-01

319

Soil solarization and chicken manure for the control of Orobanche crenata and other weeds in Lebanon  

Microsoft Academic Search

Field studies were conducted in Lebanon to investigate the effect of solarization periods (0–6wk) with or without chicken manure on Orobanche crenata seeds at various soil depths (0–10cm), and on weed management in subsequent planting of cabbage. Solarization treatments alone killed Orobanche seeds at 0 depth, but had no significant effect on Orobanche seeds below this depth. Solarization with chicken

M. A Haidar; M. M Sidahmed

2000-01-01

320

The expanded invasive weed optimization metaheuristic for solving continuous and discrete optimization problems.  

PubMed

This paper introduces an expanded version of the Invasive Weed Optimization algorithm (exIWO) distinguished by the hybrid strategy of the search space exploration proposed by the authors. The algorithm is evaluated by solving three well-known optimization problems: minimization of numerical functions, feature selection, and the Mona Lisa TSP Challenge as one of the instances of the traveling salesman problem. The achieved results are compared with analogous outcomes produced by other optimization methods reported in the literature. PMID:24955420

Josi?ski, Henryk; Kostrzewa, Daniel; Michalczuk, Agnieszka; Swito?ski, Adam

2014-01-01

321

The effect of different soil core samplers on precision of estimating weed seedbank in soil  

Microsoft Academic Search

The effect of different soil sampling procedures on the precision of estimating the weed seedbank in soil using three soil core samplers with a circular base of 1.3, 6.4 and 8.0 cm in diameter was studied in a model experiment. The results showed the importance of a methodological approach. The soil sampler with a larger diameter is more useful for

V. Smutný; J. K?en

2003-01-01

322

Sugarcane Straw and its Phytochemicals as Growth Regulators of Weed and Crop Plants  

Microsoft Academic Search

The present study investigates the effect of soil amended with sugarcane straw leachate and its constituents on root elongation\\u000a of weed and crop plants. The influence of soil biotic and abiotic factors on plant growth were also evaluated through assays\\u000a in both autoclaved soil and sand. In unsterile soil, straw leachates stimulated root growth of some test plants at 6 g

Diego A. Sampietro; Marta A. Vattuone

2006-01-01

323

The Expanded Invasive Weed Optimization Metaheuristic for Solving Continuous and Discrete Optimization Problems  

PubMed Central

This paper introduces an expanded version of the Invasive Weed Optimization algorithm (exIWO) distinguished by the hybrid strategy of the search space exploration proposed by the authors. The algorithm is evaluated by solving three well-known optimization problems: minimization of numerical functions, feature selection, and the Mona Lisa TSP Challenge as one of the instances of the traveling salesman problem. The achieved results are compared with analogous outcomes produced by other optimization methods reported in the literature.

Josinski, Henryk; Michalczuk, Agnieszka; Switonski, Adam

2014-01-01

324

Associations of segetal weed plants in the agrocenoses near the Ob River. Communication 2  

Microsoft Academic Search

Eight associations of weed vegetation in the cereal-fallow rotation and unchangeable wheat in leached chernozems of the areas\\u000a near the Ob River have been revealed as a result of 17 years of study. Five of these associations were analyzed. The associations\\u000a of segetal communities were largely affected by the long-term permanent agrocenotic factor.

V. E. Sineshchekov; A. G. Krasnoperov; E. M. Krasnoperova

2008-01-01

325

Genetic variation in the response of the weed Ruellia nudiflora (Acanthaceae) to arbuscular mycorrhizal fungi  

Microsoft Academic Search

The main goal of this work was to test for plant genetic variation in the phenotypic plasticity response of the weed Ruellia nudiflora to arbuscular mycorrhizal (AM) fungi inoculation. We collected plants in the field, kept them under homogeneous conditions\\u000a inside a nursery, and then collected seeds from these parent plants to generate five inbred lines (i.e., genetic families).\\u000a Half

José Alberto Ramos-Zapata; María José Campos-Navarrete; Víctor Parra-Tabla; Luis Abdala-Roberts; Jorge Navarro-Alberto

2010-01-01

326

Disturbance persistence in managed grasslands: shifts in aboveground community structure and the weed seed bank  

Microsoft Academic Search

The length of time and form in which disturbances persist in systems depends on the intensity and frequency of disturbance\\u000a and on the abilities of resident species to recover from such events. In grazed grasslands, trampling by large mammalian herbivores\\u000a can periodically facilitate weed establishment by exposing patches of bare ground but whether an intense soil disturbance\\u000a event results in

Ian J. Renne; Benjamin F. Tracy

2007-01-01

327

Chemical and Physical Defense of Weed Seeds in Relation to Soil Seedbank Persistence  

Microsoft Academic Search

Effective weed seedbank management requires mechanistic understanding of ecological determinants of seed persistence in the soil seedbank. Chemical and physical defense of common lambsquarters, field pennycress, giant foxtail, kochia, velvetleaf, and yellow foxtail seeds were quantified in relation to short- and long-term seedbank persistence. Seed content of ortho-dihydroxyphenols (o-DHP), a class of putative seed defense compounds, varied more than threefold

Adam S. Davis; Brian J. Schutte; James Iannuzzi; Karen A. Renner

2008-01-01

328

An Effective Means of Biofiltration of Heavy Metal Contaminated Water Bodies Using Aquatic Weed Eichhornia crassipes  

Microsoft Academic Search

Various aquatic plant species are known to accumulate heavy metals through the process of bioaccumulation. World’s most troublesome\\u000a aquatic weed water hyacinth (Eichhornia crassipes) has been studied for its tendency to bio-accumulate and bio-magnify the heavy metal contaminants present in water bodies.\\u000a The chemical investigation of plant parts has shown that it accumulates heavy metals like lead (Pb), chromium (Cr),

Suchi Tiwari; Savita Dixit; Neelam Verma

2007-01-01

329

Sunflower yield related to multi-temporal aerial photography, land elevation and weed infestation  

Microsoft Academic Search

This study investigated the relationships between sunflower yield and crop multi-temporal spectral data obtained from aerial\\u000a photographs, land elevation and the presence of Ridolfia segetum weed. Conventional-color and color-infrared airborne photographs were taken at three dates corresponding to the vegetative,\\u000a flowering and senescent crop stages. Descriptive and statistical methods were applied to every spatial variable to extract\\u000a the influence of

José M. Peña-Barragán; Francisca López-Granados; Montserrat Jurado-Expósito; Luis García-Torres

2010-01-01

330

Modelling Weed Distribution Across the Northern Australia Using Very Extensive Transects  

Microsoft Academic Search

\\u000a A Generalised Additive Modelling (GAM) approach is used to predict weed occurrence across the Top End of the Northern Territory,\\u000a Australia. The availability of new toolsets such as GRASP (Generalised Regression Analysis and Spatial Predictions) and the\\u000a application of novel GIS variables, including remotely sensed Radiometric data, Infrastructure density (roads and fences)\\u000a mapping and Climate layers, provide a useful framework

C. Hempel; N. Preece; K. Harvey; J. C. Z. Woinarski

331

Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds  

PubMed Central

Multiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, AmGSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward AmGSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management.

Cummins, Ian; Wortley, David J.; Sabbadin, Federico; He, Zhesi; Coxon, Christopher R.; Straker, Hannah E.; Sellars, Jonathan D.; Knight, Kathryn; Hughes, David; Kaundun, Shiv Shankhar; Hutchings, Sarah-Jane; Steel, Patrick G.; Edwards, Robert

2013-01-01

332

Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds.  

PubMed

Multiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, AmGSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward AmGSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management. PMID:23530204

Cummins, Ian; Wortley, David J; Sabbadin, Federico; He, Zhesi; Coxon, Christopher R; Straker, Hannah E; Sellars, Jonathan D; Knight, Kathryn; Edwards, Lesley; Hughes, David; Kaundun, Shiv Shankhar; Hutchings, Sarah-Jane; Steel, Patrick G; Edwards, Robert

2013-04-01

333

The Mechanism of Methylated Seed Oil on Enhancing Biological Efficacy of Topramezone on Weeds  

PubMed Central

Methylated seed oil (MSO) is a recommended adjuvant for the newly registered herbicide topramezone in China and also in other countries of the world, but the mechanism of MSO enhancing topramezone efficacy is still not clear. Greenhouse and laboratory experiments were conducted to determine the effects of MSO on efficacy, solution property, droplet spread and evaporation, active ingredient deposition, foliar absorption and translocation of topramezone applied to giant foxtail (Setaria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.). Experimental results showed that 0.3% MSO enhanced the efficacy of topramezone by 1.5-fold on giant foxtail and by 1.0-fold on velvetleaf. When this herbicide was mixed with MSO, its solution surface tension and leaf contact angle decreased significantly, its spread areas on weed leaf surfaces increased significantly, its wetting time was shortened on giant foxtail but not changed on velvetleaf, and less of its active ingredient crystal was observed on the treated weed leaf surfaces. MSO increased the absorption of topramezone by 68.9% for giant foxtail and by 45.9% for velvetleaf 24 hours after treatment. It also apparently promoted the translocation of this herbicide in these two weeds.

Zhang, Jinwei; Jaeck, Ortrud; Menegat, Alexander; Zhang, Zongjian; Gerhards, Roland; Ni, Hanwen

2013-01-01

334

Development of a guideline on vegetation area to reduce the risk of weed pollinosis in Korea  

NASA Astrophysics Data System (ADS)

Allergenic pollens are influenced by the environmental conditions so that the daily number of pollens varies by temperature, humidity, wind speed, etc. The relationship between the daily pollens and meteorological conditions were determined and utilized to forecast daily risk level of pollen allergy in Korea. Another important factor for the daily risk level of pollens is the vegetation area of the allergenic plants. In this study, the relationship between the area and pollen concentration was identified for two major weed species: Ragweed and Japanese Hop. It was then utilized to determine the upper limit of vegetation area to confine the risk level to a certain degree in the field. Three sites with different levels of pollen concentration were selected among twelve pollen observation sites in Korea based on the historical observation of the weed pollens. The vegetation area of the two weed species within four square kilometers at each site was surveyed. The maximum daily pollen concentration was highly correlated with the vegetation area and it was selected as a dependent variable for the regression equations, which were used as the guideline for vegetation area. According to the guideline, to limit the maximum daily pollen concentration under the moderate risk level or less than 50 pollen grains per cubic meter for Ragweed, the vegetation area should remain less than 0.6% of the ground area. For the moderate risk of Japanese Hop, pollen grains should be limited less than 100 and the area be less than 0.4%.

Rang Kim, Kyu; Lee, Hye-Rim; Kim, Mijin; Baek, Won-ki; Oh, Jae-Won; Choi, Young-Jean; Jung, Hyun-Sook

2013-04-01

335

Evaluation of biomass of some invasive weed species as substrate for oyster mushroom (Pleurotus spp.) cultivation.  

PubMed

This study assessed the bioconversion of Agriculture wastes like invasive weeds species (Lantana camara, Prosopis juliflora, Parthenium hysterophorus) as a substrate for oyster mushroom (Pleurotus species) cultivation together with wheat straw as a control. The experiment was laid out in factorial combination of substrates and three edible oyster mushroom species in a Completely Randomized Design (CRD) with three replications. Pleurotus ostreatus gave significantly (p < 0.01) total yield of 840 g kg(-1) on P. hysterophorus, Significantly (p < 0.01) biological efficiency (83.87%) and production rate of 3.13 was recorded for P. ostreatus grown on P. hysterophorus. The highest total ash content (13.90%) was recorded for P. florida grown on L. camara. while the lowest (6.92%) was for P. sajor-caju grown on the P. juliflora. Crude protein ranged from 40.51-41.48% for P. florida grown on P. hysterophorus and L. camara. Lowest crude protein content (30.11%) was recorded for P. ostreatus grown on wheat straw. The crude fiber content (12.73%) of P. sajor-caju grown on wheat straw was the highest. The lowest crude fiber (5.19%) was recorded for P. ostreatus on P. juliflora. Total yield had a positive and significant correlation with biological efficiency and production. Utilization of the plant biomass for mushroom cultivation could contribute to alleviating ecological impact of invasive weed species while offering practical option to mitigating hunger and malnutrition in areas where the invasive weeds became dominant. PMID:24783804

Mintesnot, Birara; Ayalew, Amare; Kebede, Ameha

2014-01-15

336

Invertebrate community composition differs between invasive herb alligator weed and native sedges  

NASA Astrophysics Data System (ADS)

Chemical and/or architectural differences between native and exotic plants may influence invertebrate community composition. According to the enemy release hypothesis, invasive weeds should host fewer and less specialised invertebrates than native vegetation. Invertebrate communities were compared on invasive Alternanthera philoxeroides (alligator weed) and native sedges (Isolepis prolifer and Schoenoplectus tabernaemontani) in a New Zealand lake. A. philoxeroides is more architecturally and chemically similar to I. prolifer than to S. tabernaemontani. Lower invertebrate abundance, richness and proportionally fewer specialists were predicted on A. philoxeroides compared to native sedges, but with greatest differences between A. philoxeroides and S. tabernaemontani. A. philoxeroides is more architecturally and chemically similar to I. prolifer than to S. tabernaemontani. Invertebrate abundance showed taxa-specific responses, rather than consistently lower abundance on A. philoxeroides. Nevertheless, as predicted, invertebrate fauna of A. philoxeroides was more similar to that of I. prolifer than to S. tabernaemontani. The prediction of a depauperate native fauna on A. philoxeroides received support from some but not all taxa. All vegetation types hosted generalist-dominated invertebrate communities with simple guild structures. The enemy release hypothesis thus had minimal ability to predict patterns in this system. Results suggest the extent of architectural and chemical differences between native and invasive vegetation may be useful in predicting the extent to which they will host different invertebrate communities. However, invertebrate ecology also affects whether invertebrate taxa respond positively or negatively to weed invasion. Thus, exotic vegetation may support distinct invertebrate communities despite similar overall invertebrate abundance to native vegetation.

Bassett, Imogen E.; Paynter, Quentin; Beggs, Jacqueline R.

2012-05-01

337

Robust hyperspectral vision-based classification for multi-season weed mapping  

NASA Astrophysics Data System (ADS)

This study investigated the robustness of hyperspectral image-based plant recognition to seasonal variability in a natural farming environment in the context of automated in-row weed control. A machine vision system was developed and equipped with a CCD camera integrated with a line-imaging spectrograph for close-range weed sensing and mapping. Three canonical Bayesian classifiers were developed using canopy reflectance (400-795 nm) collected over three seasons for tomato and weeds. The performance of the three season-specific classifiers was tested by changing environmental conditions, resulting in an increase in total error rate of up to 36%. Global calibration across the complete span of the three seasons produced overall classification accuracies of 85.0%, 90.0% and 92.7%, respectively, for 2005, 2006 and 2008. To improve the stability of global classifier over multiple seasons, a multiclassifier system was constructed with three canonical Bayesian classifiers optimized for the three seasons individually. This system was tested on a data set simulating an upcoming season with field conditions similar to that in 2005. The system increased the total discrimination accuracy to 95.8% for the tested season under simulation. This method provided an innovative direction for achieving robust plant recognition over multiple seasons by integrating expert knowledge from historical data that most closely matched the new field environment.

Zhang, Yun; Slaughter, David C.; Staab, Erik S.

2012-04-01

338

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

PubMed

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

Gomaa, Nasr H

2012-07-01

339

Benzoxazinoids in rye allelopathy - from discovery to application in sustainable weed control and organic farming.  

PubMed

The allelopathic potency of rye (Secale cereale L.) is due mainly to the presence of phytotoxic benzoxazinones-compounds whose biosynthesis is developmentally regulated, with the highest accumulation in young tissue and a dependency on cultivar and environmental influences. Benzoxazinones can be released from residues of greenhouse-grown rye at levels between 12 and 20 kg/ha, with lower amounts exuded by living plants. In soil, benzoxazinones are subject to a cascade of transformation reactions, and levels in the range 0.5-5 kg/ha have been reported. Starting with the accumulation of less toxic benzoxazolinones, the transformation reactions in soil primarily lead to the production of phenoxazinones, acetamides, and malonamic acids. These reactions are associated with microbial activity in the soil. In addition to benzoxazinones, benzoxazolin-2(3H)-one (BOA) has been investigated for phytotoxic effects in weeds and crops. Exposure to BOA affects transcriptome, proteome, and metabolome patterns of the seedlings, inhibits germination and growth, and can induce death of sensitive species. Differences in the sensitivity of cultivars and ecotypes are due to different species-dependent strategies that have evolved to cope with BOA. These strategies include the rapid activation of detoxification reactions and extrusion of detoxified compounds. In contrast to sensitive ecotypes, tolerant ecotypes are less affected by exposure to BOA. Like the original compounds BOA and MBOA, all exuded detoxification products are converted to phenoxazinones, which can be degraded by several specialized fungi via the Fenton reaction. Because of their selectivity, specific activity, and presumably limited persistence in the soil, benzoxazinoids or rye residues are suitable means for weed control. In fact, rye is one of the best cool season cover crops and widely used because of its excellent weed suppressive potential. Breeding of benzoxazinoid resistant crops and of rye with high benzoxazinoid contents, as well as a better understanding of the soil persistence of phenoxazinones, of the weed resistance against benzoxazinoids, and of how allelopathic interactions are influenced by cultural practices, would provide the means to include allelopathic rye varieties in organic cropping systems for weed control. PMID:23385365

Schulz, Margot; Marocco, Adriano; Tabaglio, Vincenzo; Macias, Francisco A; Molinillo, Jose M G

2013-02-01

340

DNA Analysis of Herbarium Specimens of the Grass Weed Alopecurus myosuroides Reveals Herbicide Resistance Pre-Dated Herbicides  

PubMed Central

Acetyl-CoA carboxylase (ACCase) alleles carrying one point mutation that confers resistance to herbicides have been identified in arable grass weed populations where resistance has evolved under the selective pressure of herbicides. In an effort to determine whether herbicide resistance evolves from newly arisen mutations or from standing genetic variation in weed populations, we used herbarium specimens of the grass weed Alopecurus myosuroides to seek mutant ACCase alleles carrying an isoleucine-to-leucine substitution at codon 1781 that endows herbicide resistance. These specimens had been collected between 1788 and 1975, i.e., prior to the commercial release of herbicides inhibiting ACCase. Among the 734 specimens investigated, 685 yielded DNA suitable for PCR. Genotyping the ACCase locus using the derived Cleaved Amplified Polymorphic Sequence (dCAPS) technique identified one heterozygous mutant specimen that had been collected in 1888. Occurrence of a mutant codon encoding a leucine residue at codon 1781 at the heterozygous state was confirmed in this specimen by sequencing, clearly demonstrating that resistance to herbicides can pre-date herbicides in weeds. We conclude that point mutations endowing resistance to herbicides without having associated deleterious pleiotropic effects can be present in weed populations as part of their standing genetic variation, in frequencies higher than the mutation frequency, thereby facilitating their subsequent selection by herbicide applications.

Delye, Christophe; Deulvot, Chrystel; Chauvel, Bruno

2013-01-01

341

Evaluation of Selected Herbicides for the Control of Exotic Submerged Weeds in New Zealand: I. The Use of Endothall, Triclopyr and Dichlobenil  

Microsoft Academic Search

The aquatic herbicide diquat is the only product regis- tered in New Zealand for controlling the submerged weeds lagarosiphon (Lagarosiphon major (Ridley) Wager), hornwort (in New Zealand) or coontail (Ceratophyllum demersum L), egeria (Egeria densa Planch), and hydrilla (Hydrilla verticillata (Lf) Royle). However, diquat can be ineffective under some environmental conditions and it does not control certain submerged weeds. Greenhouse

DEBORAH E. HOFSTRA; JOHN S. CLAYTON

2001-01-01

342

Enhancement in the Efficiency of Existing Oxidation Ponds by Using Aquatic Weeds at Little or No Extra Cost—The Macrophyte-Upgraded Oxidation Pond (MUOP)  

Microsoft Academic Search

All over the world, tens of thousands of oxidation ponds are in operation treating sewage and other biodegradable wastewaters. The performance of such ponds can be greatly enhanced if certain aquatic weeds are held in them. The weeds enable better treatment of wastewater in terms of greater reduction in the biochemical oxygen demand (BOD), suspended solids, nitrogen, phosphorous, metals, etc.,

Tasneem Abbasi; S. A. Abbasi

2010-01-01

343

PROCEEDINGS OF THE WORKSHOP ON AQUATIC WEEDS: CONTROL AND ITS ENVIRONMENTAL CONSEQUENCES HELD AT GULF BREEZE, FLORIDA ON FEBRUARY 25-26, 1980  

EPA Science Inventory

The report reviews the state-of-the-art of the chemical, biological, mechanical, and integrated control of aquatic weeds. Participants discuss problems in the field of aquatic weed control and the role of EPA in working toward their solution. Guidelines are proposed for the evalu...

344

Survival of weed seeds and animal parasites as affected by anaerobic digestion at meso- and thermophilic conditions.  

PubMed

Anaerobic digestion of residual materials from animals and crops offers an opportunity to simultaneously produce bioenergy and plant fertilizers at single farms and in farm communities where input substrate materials and resulting digested residues are shared among member farms. A surplus benefit from this practice may be the suppressing of propagules from harmful biological pests like weeds and animal pathogens (e.g. parasites). In the present work, batch experiments were performed, where survival of seeds of seven species of weeds and non-embryonated eggs of the large roundworm of pigs, Ascaris suum, was assessed under conditions similar to biogas plants managed at meso- (37°C) and thermophilic (55°C) conditions. Cattle manure was used as digestion substrate and experimental units were sampled destructively over time. Regarding weed seeds, the effect of thermophilic conditions (55°C) was very clear as complete mortality, irrespective of weed species, was reached after less than 2 days. At mesophilic conditions, seeds of Avena fatua, Sinapsis arvensis, Solidago canadensis had completely lost germination ability, while Brassica napus, Fallopia convolvulus and Amzinckia micrantha still maintained low levels (~1%) of germination ability after 1 week. Chenopodium album was the only weed species which survived 1 week at substantial levels (7%) although after 11 d germination ability was totally lost. Similarly, at 55°C, no Ascaris eggs survived more than 3h of incubation. Incubation at 37°C did not affect egg survival during the first 48 h and it took up to 10 days before total elimination was reached. In general, anaerobic digestion in biogas plants seems an efficient way (thermophilic more efficient than mesophilic) to treat organic farm wastes in a way that suppresses animal parasites and weeds so that the digestates can be applied without risking spread of these pests. PMID:23266071

Johansen, Anders; Nielsen, Henrik B; Hansen, Christian M; Andreasen, Christian; Carlsgart, Josefine; Hauggard-Nielsen, Henrik; Roepstorff, Allan

2013-04-01

345

An analysis of assessment outcomes from eight years' operation of the Australian border weed risk assessment system.  

PubMed

The majority of Australian weeds are exotic plant species that were intentionally introduced for a variety of horticultural and agricultural purposes. A border weed risk assessment system (WRA) was implemented in 1997 in order to reduce the high economic costs and massive environmental damage associated with introducing serious weeds. We review the behaviour of this system with regard to eight years of data collected from the assessment of species proposed for importation or held within genetic resource centres in Australia. From a taxonomic perspective, species from the Chenopodiaceae and Poaceae were most likely to be rejected and those from the Arecaceae and Flacourtiaceae were most likely to be accepted. Dendrogram analysis and classification and regression tree (TREE) models were also used to analyse the data. The latter revealed that a small subset of the 35 variables assessed was highly associated with the outcome of the original assessment. The TREE model examining all of the data contained just five variables: unintentional human dispersal, congeneric weed, weed elsewhere, tolerates or benefits from mutilation, cultivation or fire, and reproduction by vegetative propagation. It gave the same outcome as the full WRA model for 71% of species. Weed elsewhere was not the first splitting variable in this model, indicating that the WRA has a capacity for capturing species that have no history of weediness. A reduced TREE model (in which human-mediated variables had been removed) contained four variables: broad climate suitability, reproduction in less or than equal to 1year, self-fertilisation, and tolerates and benefits from mutilation, cultivation or fire. It yielded the same outcome as the full WRA model for 65% of species. Data inconsistencies and the relative importance of questions are discussed, with some recommendations made for improving the use of the system. PMID:18339471

Weber, Jason; Dane Panetta, F; Virtue, John; Pheloung, Paul

2009-02-01

346

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

PubMed Central

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.

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

347

[Host weeds of Rhopalosiphum rufiabdominalis (Sasaki) (Hemiptera: Aphididae) in areas of irrigated rice].  

PubMed

Rhopalosiphum rufiabdominalis (Sasaki) is an insect of world-wide distribution that damages irrigated rice. From September, 2004 to February, 2005, nymphs and adults of this aphid were collected in several host weeds of rice farms in Alegrete, Quaraí and Uruguaiana, located in Western of State of Rio Grande do Sul, and Restinga Seca, in Central region of this State, Brazil. The insect was found in the root of Andropogon bicornis (West Indian foxtail), Echinochloa colona (jungle rice), Oryza sativa (volunteer rice and red-rice), Paspalum sp. (paspalum) and Soliva pterosperma (lawn burweed). PMID:17710332

Maziero, Heleno; Guedes, Jerson V C; Kruse, Nelson D; Farias, Juliano R

2007-01-01

348

Anethofuran, carvone, and limonene: potential cancer chemopreventive agents from dill weed oil and caraway oil.  

PubMed

Bioassay-directed fractionation of dill weed oil and caraway oil, respectively, from the plants Anethum graveolens L. and Carum carvi L. (Umbelliferae) has led to the isolation of three monoterpenes, anethofuran (1), carvone (2), and limonene (3). Their structures were determined on the basis of spectral analysis. These compounds induced the detoxifying enzyme glutathione S-transferase in several mouse target tissues. The alpha,beta-unsaturated ketone system in carvone appeared to be critical for the high enzyme-inducing activity. PMID:1438594

Zheng, G Q; Kenney, P M; Lam, L K

1992-08-01

349

Durum wheat and allelopathy: toward wheat breeding for natural weed management.  

PubMed

Wheat-derived foodstuffs represent about one-fifth of the calories consumed by humans worldwide. Bread wheat (Triticum aestivum L.) is one of the most important crops throughout the world, and it has been extensively studied for its allelopathic potential. In contrast, for allelopathy in durum wheat (Triticum turgidum ssp. durum), our knowledge is partial and fragmentary. Through highlighting recent advances in using allelopathy as a crop-breeding tool, we provide an overview of allelopathy in Triticum spp., to stimulate further coordinated breeding-oriented studies, to favor allelopathy exploitation for the sustainable cultivation of wheat, and in particular, to achieve improved biological weed control. PMID:24065979

Fragasso, Mariagiovanna; Iannucci, Anna; Papa, Roberto

2013-01-01

350

Bidens pilosa L. exhibits high sensitivity to coumarin in comparison with three other weed species.  

PubMed

Nine natural plant compounds were screened for phytotoxicity to Bidens pilosa L. a troublesome weed in field and plantation crops. The sensitivity of three other weed species to coumarin, the most active identified compound, was also evaluated. Coumarin, at a concentration of 500 microM, had little effect on germination and growth of Senna obtusifolia L., Euphorbia heterophylla L., and Ipomoea grandifolia L. when compared with its effects on B. pilosa L. In a concentration range of 10-100 microM, coumarin caused a dose-dependent inhibition of germination and growth of B. pilosa L. The measurements of some parameters of energy metabolism revealed that coumarin-treated root tissues exhibited characteristics of seedlings in an earlier stage of growth, including higher respiratory activity and higher activities of alcohol dehydrogenase and lipoxygenase. These results suggest that coumarin inhibition of germination and growth of B. pilosa L. was not a consequence of an impairment of energy metabolism. Rather, it seems to act as a cytostatic agent, retarding germination. At concentrations above 50 microM, coumarin increased lipoxygenase activity and the level of conjugated dienes of root extracts, suggesting that it may induce oxidative stress in seedling roots. PMID:18338136

Pergo, Erica Marusa; Abrahim, Denise; Soares da Silva, Patrícia Cristina; Kern, Kátia Aparecida; Da Silva, Lucas Jonatas; Voll, Elemar; Ishii-Iwamoto, Emy Luiza

2008-04-01

351

Cadmium accumulation characteristics of the winter farmland weeds Cardamine hirsuta Linn. and Gnaphalium affine D. Don.  

PubMed

In a preliminary study, we found that the cadmium (Cd) concentrations in shoots of the winter farmland weeds Cardamine hirsuta Linn. and Gnaphalium affine D. Don exceeded the critical value of a Cd-hyperaccumulator (100 mg kg(-1)), indicating that these two farmland weeds might be Cd-hyperaccumulators. In this study, we grew these species in soil containing various concentrations of Cd to further evaluate their Cd accumulation characteristics. The biomasses of C. hirsuta and G. affine decreased with increasing Cd concentrations in the soil, while the root/shoot ratio and the Cd concentrations in shoot tissues increased. The Cd concentrations in shoots of C. hirsuta and G. affine reached 121.96 and 143.91 mg kg(-1), respectively, at the soil Cd concentration of 50 mg kg(-1). Both of these concentrations exceeded the critical value of a Cd-hyperaccumulator (100 mg kg(-1)). The shoot bioconcentration factors of C. hirsuta and G. affine were greater than 1. The translocation factor of C. hirsuta was less than 1 and that of G. affine was greater than 1. These findings indicated that C. hirsuta is a Cd-accumulator and G. affine is Cd-hyperaccumulator. Both plants are distributed widely in the field, and they could be used to remediate Cd-contaminated farmland soil in winter. PMID:24519638

Lin, Lijin; Shi, Jun; Liu, Qihua; Liao, Ming'an; Mei, Luoyin

2014-07-01

352

Weed control and persistence of two oxyfluorfen formulations in olive groves under non tillage conditions.  

PubMed

To obtain profitable yields in olive groves, residual preemergence herbicides are applied in October or November before the winter rains, and before the winter annual weeds germinate. Simazine, one of the herbicides most used for weed control in olive groves, has recently been banned. Oxyfluorfen is presented as a good alternative to simazine in olive fields. Experiments were carried out in 2002 and 2003 to evaluate the behaviour of two oxyfluorfen formulations, 2XL and G4F, at 480 g a.i. ha(-1) for three different soil management systems with three replications (1. bare soil; 2. bare soil and grassed buffer strips, chemically controlled and 3. bare soil and grassed buffer strips with controlled mowing; under non tillage conditions in all three cases). The most important species that survived 2XL and G4F treatments was Sagina apetala ARD. Oxyfluorfen residues were evaluated throughout 158 days after the applications. Three soil samples from each plot were collected, mixed and air dried. The herbicide extractions were made with methanol and the residues were analyzed by HPLC. We found no differences between the two formulations, but results showed that recoveries of oxyfluorfen were higher in plots with chemically controlled buffer grassed strips than in the other soil management types. PMID:15765564

Martínez, M J; Farsaoui, K; de Prado, R

2004-01-01

353

Reproduction of Pratylenchus penetrans on 24 Common Weeds in Potato Fields in Qu?bec  

PubMed Central

Twenty-four weeds commonly found in commercial potato fields in Quebec were evaluated for their host suitability to the root-lesion nematode, Pratylenchus penetrans, under greenhouse conditions. Brown mustard (Brassica juncea) and rye (Secale cereale) were included as susceptible controls and forage pearl millet hyb. CFPM 101 (Pennisetum glaucum) as a poor host. Pratylenchus penetrans multiplied well on 22 of the 24 weed species tested (Pf/Pi ? rye or brown mustard). Cirsium arvense, Leucanthemum vulgare and Matricaria discoida were classified as very good hosts with a Pf/Pi ranging from 1.60 to 2.54, while Ambrosia artemisiifolia and Cyperus esculentus were classified as poor hosts with a Pf/Pi from 0.01 to 0.15. Amaranthus powellii, A. retrqflexus, Raphanus raphanistrum, Rorippa palustris, Cerastium fontanum, Spergula arvensis, Stellaria media, Chenopodium album, Vicia cracca, Elytrigia repens, Digitaria ischaemum, Echinochloa crusgalli, Panicum capillare, Setaria faberii, S. pumila, S. viridis, Polygonum convolvulus, P. scabrum and P. persicaria were intermediate hosts with Pf/Pi values ranging from 0.33 to 2.01. The plant species and the botanical family had a significant impact on nematode reproduction. The Brassicaceae family resulted in the greatest reproduction of P. penetrans, and the Cyperaceae resulted in the least. The plant life-cycle (annual vs. perennial) had no impact on nematode population.

Belair, G.; Dauphinais, N.; Benoit, D. L.; Fournier, Y.

2007-01-01

354

Morphological responses of crop and weed species of different growth forms to ultraviolet-B radiation  

SciTech Connect

Recent evidence of a general, global decline of stratospheric ozone has heightened concern about possible ecological consequences of increases in solar ultraviolet-B (UV-B, 280-320 nm) radiation resulting from ozone depletion. The influence of UV-B radiation (280-320 nanometers) on the morphology of 12 common dicot and monocot crop or weed species was examined to determine whether any common responses could be found that might, in turn, be useful in predicting possible changes in competitive balance under solar UV-B enhancement. Under glasshouse conditions, UV-B exposure (simulating a 20% reduction in stratospheric ozone at Logan, Utah) was found to reduce leaf blade and internode lengths and increase leaf and axillary shoot production in several species. Overall, the directions of these trends were similar in the majority of species that exhibited a significant response. These morphological changes occurred without any significant reduction in total shoot dry matter production. There was no clear distinction in the response of crops and weeds, though monocots were found to be generally more responsive than dicots. Previous work in dense canopies has shown that the photomorphogenetic effects of UV-B alter leaf placement and thereby influence competition for light. Our results suggest that, under these conditions, changes in competitive balance resulting from increased UV-B might be expected more frequently when monocots are involved in mixtures, rather than mixtures of only dicots.

Barnes, P.W.; Flint, S.D.; Caldwell, M.M. (Utah State Univ., Logan (USA))

1990-10-01

355

Lamium amplexicaule (Lamiaceae): a weed reservoir for tomato yellow leaf curl virus (TYLCV) in Korea.  

PubMed

After the first identification of tomato yellow leaf curl virus (TYLCV) in the southern part of Korea in 2008, TYLCV has rapidly spread to tomato farms in most regions of Korea. From 2008 to 2010, a survey of natural weed hosts that could be reservoirs of TYLCV was performed in major tomato production areas of Korea. About 530 samples were collected and identified as belonging to 25 species from 11 families. PCR and Southern hybridization were used to detect TYLCV in samples, and replicating forms of TYLCV DNA were detected in three species (Achyranthes bidentata, Lamium amplexicaule, and Veronica persica) by Southern hybridization. TYLCV transmission mediated by Bemisia tabaci from TYLCV-infected tomato plants to L. amplexicaule was confirmed, and TYLCV-infected L. amplexicaule showed symptoms such as yellowing, stunting, and leaf curling. TYLCV from infected L. amplexicaule was also transmitted to healthy tomato and L. amplexicaule plants by B. tabaci. The rate of infection of L. amplexicaule by TYLCV was similar to that of tomato. This report is the first to show that L. amplexicaule is a reservoir weed host for TYLCV. PMID:24327090

Kil, Eui-Joon; Park, Jungan; Lee, Hyejung; Kim, Jaedeok; Choi, Hong-Soo; Lee, Kyeong-Yeoll; Kim, Chang-Seok; Lee, Sukchan

2014-06-01

356

Influence of type and amount of straw cover on weed emergence.  

PubMed

This research was undertaken during 2003-2004 growing season to evaluate the effects of type [forage sorghum "hybrid Cober Exp" (Sorghum bicolor x Sorghum sudanense), forage millet (Pennisetum americanum "var. BN2"), finger millet (Eleusine coracana), and St Lucia grass (Brachiaria brizantha)] and amount of straw cover (5.5 and 3.0 t ha(-1)) upon the emergence of Bidens pilosa, Chamaesyce spp., Amaranthus spp., and Commelina benghalensis, under field conditions of the Brazilian Cerrado, in the region of Uberlândia--MG. The control consisted additional treatment lacking the straw cover. Emergence of weed depended on the type and amount of straw cover, as well as the weed species. The lowest number of B. pilosa seedlings was found in the presence of forage sorghum straw; Chamaesyce spp. in the lack of straw; Amaranthus spp. in the presence of higher amount of forage sorghum and forage millet, and lower amounts of forage millet and Finger Millet. All the types and amounts of straw reduced the emergency of C. benghalensis, except at the lowest level of St Lucia grass and the lack of straw. PMID:15656176

Correia, Núbia Maria; Durigan, Julio Cezar; Klink, Urubatan Palhares

2005-01-01

357

Screen of Chinese weed species for cadmium tolerance and accumulation characteristics.  

PubMed

The cadmium (Cd) tolerance and metal-accumulation characteristics of 29 species (18 families) of weed were studied by using outdoor pot-culture experiments. The results of this screening showed that Bidens pilosa and Kalimeris integrifolia (both Asteraceae) expressed some properties that are characteristic of Cd hyperaccumulators. In 10 mg/kg Cd-spiked soil, they accumulated a good deal of Cd in shoots (28 and 25 mg/kg DW, respectively) with high Cd enrichment factors (EFs; concentration in plant/soil). Cd accumulations in shoots were greater than those in roots (translocation factor (TF) >1, concentration in shoot/root) and the shoot biomasses did not decreased significantly compared to the unspiked control. The other weed species showed little accumulation of Cd, Pb, Cu, or Zn. In a concentration-gradient experiment, the Cd accumulation potentials of B. pilosa and K. integrifolia were examined further. Cd concentrations in leaves of B. pilosa growing in soils spiked with 25, 50, and 100 mg/kg Cd were up to 145, 160, and 192 mg/kg, respectively, and the Cd content in stems in the 100 mg/kg Cd-spiked soil was 115 mg/kg, all greater than the 100 mg/kg notional criterion for Cd hyperaccumulation. The Cd EFs and TFs were all greater than 1. The shoot biomasses did not decrease significantly compared to the controls. B. pilosa was thus shown to have some characteristics of a true Cd hyperaccumulator plant. PMID:19260234

Wei, Shuhe; Zhou, Qixing

2008-01-01

358

Chitosan/tripolyphosphate nanoparticles loaded with paraquat herbicide: An environmentally safer alternative for weed control.  

PubMed

Paraquat is a fast acting nonselective contact herbicide that is extensively used worldwide. However, the aqueous solubility and soil sorption of this compound can cause problems of toxicity in nontarget organisms. This work investigates the preparation and characterization of nanoparticles composed of chitosan and sodium tripolyphosphate (TPP) to produce an efficient herbicidal formulation that was less toxic and could be used for safer control of weeds in agriculture. The toxicities of the formulations were evaluated using cell culture viability assays and the Allium cepa chromosome aberration test. The herbicidal activity was investigated in cultivations of maize (Zea mays) and mustard (Brassica sp.), and soil sorption of the nanoencapsulated herbicide was measured. The efficiency association of paraquat with the nanoparticles was 62.6±0.7%. Encapsulation of the herbicide resulted in changes in its diffusion and release as well as its sorption by soil. Cytotoxicity and genotoxicity assays showed that the nanoencapsulated herbicide was less toxic than the pure compound, indicating its potential to control weeds while at the same time reducing environmental impacts. Measurements of herbicidal activity showed that the effectiveness of paraquat was preserved after encapsulation. It was concluded that the encapsulation of paraquat in nanoparticles can provide a useful means of reducing adverse impacts on human health and the environment, and that the formulation therefore has potential for use in agriculture. PMID:24968252

Grillo, Renato; Pereira, Anderson E S; Nishisaka, Caroline S; de Lima, Renata; Oehlke, Kathleen; Greiner, Ralf; Fraceto, Leonardo F

2014-08-15

359

Crops gone wild: evolution of weeds and invasives from domesticated ancestors  

PubMed Central

The evolution of problematic plants, both weeds and invasives, is a topic of increasing interest. Plants that have evolved from domesticated ancestors have certain advantages for study. Because of their economic importance, domesticated plants are generally well-characterized and readily available for ecogenetic comparison with their wild descendants. Thus, the evolutionary history of crop descendants has the potential to be reconstructed in some detail. Furthermore, growing crop progenitors with their problematic descendants in a common environment allows for the identification of significant evolutionary differences that correlate with weediness or invasiveness. We sought well-established examples of invasives and weeds for which genetic and/or ethnobotanical evidence has confirmed their evolution from domesticates. We found surprisingly few cases, only 13. We examine our list for generalizations and then some selected cases to reveal how plant pests have evolved from domesticates. Despite their potential utility, crop descendants remain underexploited for evolutionary study. Promising evolutionary research opportunities for these systems are abundant and worthy of pursuit.

Ellstrand, Norman C; Heredia, Sylvia M; Leak-Garcia, Janet A; Heraty, Joanne M; Burger, Jutta C; Yao, Li; Nohzadeh-Malakshah, Sahar; Ridley, Caroline E

2010-01-01

360

Fungal pathogens of Euphorbia heterophylla and E. hirta in Brazil and their potential as weed biocontrol agents.  

PubMed

A two-year survey of the fungi associated with two important congeneric pantropical weeds, Euphorbia heterophylla and E. hirta, was conducted in part of their native range in southern Brazil. Sampling was concentrated mainly in Rio de Janeiro State and ten species were identified as pathogens of these weeds. Two taxa, Botrytis ricini and Uromyces euphorbiae, were common to both weed hosts. Alternaria euphorbiicola, Bipolaris euphorbiae, Melampsora sp., Oidium sp. and Sphaceloma poinsettiae were recorded only from E. heterophylla, whereas Colletotrichum gloeosporioides, Sphaceloma sp. and Sphaerotheca fuliginea were restricted to E. hirta. Botrytis ricini and Colletotrichum gloeosporioides are new records for E. hirta, and Alternaria euphorbiicola and Sphaerotheca fuliginea are new host records for Brazil. Bipolaris euphorbiae, previously identified as Helminthosporium sp., is considered to be the correct name for the causal agent of a major disease of E. heterophyllum in Brazil. The potential of these pathogens as biocontrol agents is discussed and the mycobiota associated with both these weeds worldwide is reviewed. PMID:16284862

Barreto, R W; Evans, H C

1998-01-01

361

Strip-tilled cover cropping for managing nematodes, soil mesoarthropods, and weeds in a bitter melon agroecosystem.  

PubMed

A field trial was conducted to examine whether strip-tilled cover cropping followed by living mulch practice could suppress root-knot nematode (Meloidogyne incognita) and enhance beneficial nematodes and other soil mesofauna, while suppressing weeds throughout two vegetable cropping seasons. Sunn hemp (SH), Crotalaria juncea, and French marigold (MG), Tagetes patula, were grown for three months, strip-tilled, and bitter melon (Momordica charantia) seedlings were transplanted into the tilled strips; the experiment was conducted twice (Season I and II). Strip-tilled cover cropping with SH prolonged M. incognita suppression in Season I but not in Season II where suppression was counteracted with enhanced crop growth. Sunn hemp also consistently enhanced bacterivorous and fungivorous nematode population densities prior to cash crop planting, prolonged enhancement of the Enrichment Index towards the end of both cash crop cycles, and increased numbers of soil mesoarthropods. Strip-tilled cover cropping of SH followed by clipping of the living mulch as surface mulch also reduced broadleaf weed populations up to 3 to 4 weeks after cash crop planting. However, SH failed to reduce soil disturbance as indicated by the Structure Index. Marigold suppressed M. incognita efficiently when planted immediately following a M. incognita-susceptible crop, but did not enhance beneficial soil mesofauna including free-living nematodes and soil mesoarthropods. Strip-tilled cover cropping of MG reduced broadleaf weed populations prior to cash crop planting in Season II, but this weed suppression did not last beyond the initial cash crop cycle. PMID:22736847

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

2010-06-01

362

The relative importance of allelopathy in interference: the effects of an invasive weed on a native bunchgrass  

Microsoft Academic Search

The relative importance of allelopathy and re- source competition in plant-plant interactions has been vigorously debated but seldom tested. We used activated carbon to manipulate the effects of root exudates of Centaurea maculosa, a noxious weed in much of western North America, on root elongation rates and growth of the native bunchgrass Festuca idahoensis in order to in- vestigate the

Wendy M. Ridenour; Ragan M. Callaway

2001-01-01

363

Management of Sinapis alba subsp. mairei winter cover crop residues for summer weed control in southern Spain  

Microsoft Academic Search

Sinapis alba subsp. mairei (H. Lindb. fil.) Maire, a wild subspecies of S. alba L., which is distributed throughout the Mediterranean basin, has been recently introduced in southern Spain as a winter cover crop in olive groves. The reason behind using this cover crop is for the reduction of Verticillium dahliae inoculum. The effectiveness of this cover crop for weed

C. Alcántara; A. Pujadas; M. Saavedra

2011-01-01

364

COVER CROP RESIDUE EFFECTS ON EARLY-SEASON WEED ESTABLISHMENT IN A CONSERVATION-TILLAGE CORN-COTTON ROTATION  

Microsoft Academic Search

Use of winter cover crops is an integral component of conservation systems in corn (Zea mays L.) and cotton (Gossypium hirsutum L.). A field experiment was initiated in 2004 to evaluate weed suppression provided by winter cover crops in a conservation-tillage corn and cotton rotation. Rotation for winter cover crops included clover (Trifolium incarnatum L.) preceding corn and rye (Secale

Monika Saini; Andrew Price; Edzard van Santen

2006-01-01

365

Effect of Growth Stage on the Efficacy of Postemergence Herbicides on Four Weed Species of Direct-Seeded Rice  

PubMed Central

The efficacy of bispyribac-sodium, fenoxaprop + ethoxysulfuron, and penoxsulam + cyhalofop was evaluated against barnyardgrass, Chinese sprangletop, junglerice, and southern crabgrass when applied at four-, six-, and eight-leaf stages. When applied at the four-leaf stage, bispyribac-sodium provided greater than 97% control of barnyardgrass, junglerice, and southern crabgrass; however, it was slightly weak (74% control) on Chinese sprangletop. Irrespective of the weed species, fenoxaprop + ethoxysulfuron provided greater than 97% control when applied at the four-leaf stage. At the same leaf stage, penoxsulam + cyhalofop controlled 89 to 100% barnyardgrass, Chinese sprangletop, and junglerice and only 54% of southern crabgrass. The efficacy of herbicides was reduced when applied at the eight-leaf stage of the weeds; however, at this stage, fenoxaprop + ethoxysulfuron was effective in controlling 99% of Chinese sprangletop. The results demonstrate the importance of early herbicide application in controlling the weeds. The study identified that at the six-leaf stage of the weeds, fenoxaprop + ethoxysulfuron can effectively control Chinese sprangletop and southern crabgrass, penoxsulam + cyhalofop can effectively control Chinese sprangletop, and bispyribac-sodium can effectively control junglerice.

Chauhan, Bhagirath Singh; Abugho, Seth Bernard

2012-01-01

366

COMPARISON OF THE METHODS FOR ANALYSIS OF PARTIAL SAMPLES AND OF A BULK SAMPLE AT ESTIMATING WEED SEEDBANK IN SOIL  

Microsoft Academic Search

Summary The effect of soil sampling with three core samplers of a different diameter (13, 64, and 80 mm) using the method for analysis of partial samples (MAPS) or a bulk sample (MABS) on the precision of estimating the weed seedbank in soil was studied in a model experiment. The results show that to obtain sufficiently exact data characterising the

Vladimír SMUTNÝ

367

76 FR 43706 - Final Supplementary Rules To Require the Use of Certified Noxious-Weed-Free Forage and Straw on...  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLID-931-000-L1020-0000-JP-0000252R...Noxious-Weed-Free Forage and Straw on Bureau of Land Management Lands in the State of Idaho AGENCY: Bureau of Land Management, Interior. ACTION: Final...

2011-07-21

368

A Medical Revolution That Could...: The Work of the PROMIS Laboratory and Lawrence L. Weed, M.D.  

ERIC Educational Resources Information Center

The problem-oriented medical record, developed by Lawrence L. Weed, M.D., involves an interactive computer system and has been operational on two wards at the University Hospital in Burlington, Vermont, a teaching hospital. The Problem-Oriented Medical Information System (PROMIS) consists of terminals that feed into the central memory units; the…

Cook, Gordon

369

Allelopathic potential of rhizosphere soil of Croton bonplandianum on growth and establishment of some crop and weed plants  

Microsoft Academic Search

This experiment was carried out to study various biological and ecological features of Croton bonplandianum Baill and physico-chemical characteristics of its rhizosphere soil, and determine the effect on the growth of some crop and weed plants that is Triticum aestivum L., Brassica rapa L., Brassica oleracea var. botrytis L. and Spinacea oleracea L., Melilotus alba Medik., Vicia sativa L., and

Swapnal Sisodia; M. Badruzzaman Siddiqui

370

Single step synthesis of strigolactone analogues from cyclic keto enols, germination stimulants for seeds of parasitic weeds  

Microsoft Academic Search

The single step synthesis of a newly designed series of strigolactones (SLs) from cyclic keto enols is described. The germinating activity of these SL analogues towards seeds of the parasitic weeds Striga and Orobanche spp. is reported. The first of these SL analogues are derived from the hydroxyl ?-pyrones kojic acid and maltol, the second type from hydroxyl ?-pyrones, namely,

Alinanuswe S. Mwakaboko; Binne Zwanenburg

2011-01-01

371

Reproductive modes of three Ligularia weeds (Asteraceae) in grasslands in Qinghai-Tibet Plateau and their implications for grassland management  

Microsoft Academic Search

Ligularia virgaurea, L. sagitta and L. przewalskii are noxious weeds that are widely distributed in psychro-grasslands in the east of Qinghai-Tibet Plateau of China. However, little is known about reproductive modes and genetic diversity in the populations of L. virgaurea and L. sagitta under different environmental conditions, although such information is available for L. przewalskii. In this study, two experiments

Rui-Jun Ma; Guo-Zhen Du; Bao-Rong Lu; Jia-Kuan Chen; Kun Sun; Toshihiko Hara; Bo Li

2006-01-01

372

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

NASA Astrophysics Data System (ADS)

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.

Waheed, Tahir

373

Competitive effects of introduced annual weeds on some native and reclamation species in the Powder River Basin, Wyoming  

SciTech Connect

Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Bouteloua gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B. gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)

Allen, E.B.; Knight, D.H.

1980-01-01

374

Camera sensor arrangement for crop/weed detection accuracy in agronomic images.  

PubMed

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. PMID:23549361

Romeo, Juan; Guerrero, José Miguel; Montalvo, Martín; Emmi, Luis; Guijarro, María; Gonzalez-de-Santos, Pablo; Pajares, Gonzalo

2013-01-01

375

Predicting weed migration from soil and climate maps. [Centaurea maculosa Lam  

SciTech Connect

Soil characteristics, elevation, annual precipitation, potential evapotranspiration, length of frost-free season, and mean maximum July temperature were estimated for 116 established infestations of spotted knapweed (Centaurea maculosa Lam. number/sup 3/ CENMA) in Montana using basic land resource maps. Areas potentially vulnerable to invasion by the plant were delineated on the basis of representative edaphic and climatic characteristics. No single environmental variable was an effective predictor of sites vulnerable to invasion by spotted knapweed. Only a combination of variables was effective, indicating that the factors that regulate adaptability of this plant are complex. This technique provides a first approximation map of the regions most similar environmentally to infested sites and; therefore, most vulnerable to further invasion. This weed migration prediction technique shows promise for predicting suitable habitats of other invader species. 6 references, 4 figures, 1 table.

Chicoine, T.K.; Fay, P.K.; Nielsen, G.A.

1985-01-01

376

Characterization of glucosylceramides in the Polygonaceae, Rumex obtusifolius L. injurious weed.  

PubMed

Rumex obtusifolius L., a member of Polygonaceae, is one of the world's worst weeds. We characterized the glucosylceramide molecular species in leaves of R. obtusifolius by liquid chromatography/tandem mass spectrometry. 4,8-Sphingadienines were principally paired with 2-hydroxy palmitic acids. In contrast, 4-hydroxy-8-sphingenines were chiefly attached to 2-hydroxy fatty acids with 22 to 26 carbon-chain length. A unique characteristic of the 2-hydroxy fatty acid composition of R. obtusifolius was the high content of n-9 monoenoic 2-hydroxy fatty acids with 22 and 24 carbon-chain length. The levels of the Z and E stereoisomers of the 8-unsaturated long-chain bases were reliably distinguished from those in other plant families in ten species of Polygonaceae. PMID:21597180

Watanabe, Masayuki; Miyagi, Atsuko; Nagano, Minoru; Kawai-Yamada, Maki; Imai, Hiroyuki

2011-01-01

377

Management of fresh water weeds (macrophytes) by vermicomposting using Eisenia fetida.  

PubMed

In the present study, potential of Eisenia fetida to recycle the different types of fresh water weeds (macrophytes) used as substrate in different reactors (Azolla pinnata reactor, Trapa natans reactor, Ceratophyllum demersum reactor, free-floating macrophytes mixture reactor, and submerged macrophytes mixture reactor) during 2 months experiment is investigated. E. fetida showed significant variation in number and weight among the reactors and during the different fortnights (P <0.05) with maximum in A. pinnata reactor (number 343.3?±?10.23 %; weight 98.62?±?4.23 % ) and minimum in submerged macrophytes mixture reactor (number 105?±?5.77 %; weight 41.07?±?3.97 % ). ANOVA showed significant variation in cocoon production (F4?=?15.67, P <0.05) and mean body weight (F4?=?13.49, P <0.05) among different reactors whereas growth rate (F3?=?23.62, P <0.05) and relative growth rate (F3?=?4.91, P <0.05) exhibited significant variation during different fortnights. Reactors showed significant variation (P <0.05) in pH, Electrical conductivity (EC), Organic carbon (OC), Organic nitrogen (ON), and C/N ratio during different fortnights with increase in pH, EC, N, and K whereas decrease in OC and C/N ratio. Hierarchical cluster analysis grouped five substrates (weeds) into three clusters-poor vermicompost substrates, moderate vermicompost substrate, and excellent vermicompost substrate. Two principal components (PCs) have been identified by factor analysis with a cumulative variance of 90.43 %. PC1 accounts for 47.17 % of the total variance represents "reproduction factor" and PC2 explaining 43.26 % variance representing "growth factor." Thus, the nature of macrophyte affects the growth and reproduction pattern of E. fetida among the different reactors, further the addition of A. pinnata in other macrophytes reactors can improve their recycling by E. fetida. PMID:23589265

Najar, Ishtiyaq Ahmed; Khan, Anisa B

2013-09-01

378

Possibilities of chemical weed control in Lupinus albus and Lupinus luteus-screening of herbicides.  

PubMed

Weed control in sweet lupins is still a problem. Especially the phytotoxicity of herbicides in sweet lupins is not enough studied. Therefore a screening with 16 selected herbicides and 4 lupin varieties has been set up. During the growing season 2005, 10 of the tested herbicides were applied in pre-emergence, 6 in post-emergence. Pre-emergence: Most of the active matters tested in pre-emergence were not phytotoxic for lupins. Pendimethalin (1000 g/ha), linuron (500 g/ha), chlorotoluron (1500 g/ha), prosulfocarb (2400 g/ha), clomazone (72 g/ha), isoxaben (100 g/ha), metamitron (1050 g/ha) and dimethenamid-P (720 g/ha) were applied without causing any significant phytotoxic symptoms. Only the lupins treated with aclonifen (1200 g/ha) showed a significant growth inhibition, 3 weeks after treatment. Significantly more chlorosis was noticed when the lupins were treated with aclonifen or with diflufenican, in preemergence. Post-emergence: In post-emergence, diflufenican (50 g/ha) did not cause any crop damage. Florasulam (5 g/ha) caused almost 100% necrosis in L. albus as well as in L. luteus. Bentazon (652 g/ha), thifensulfuron-methyl (15 g/ha) and metribuzin (175 g/ha) caused obvious necrosis and growth inhibition of the crop. The growth inhibition was significantly more severe for lupins treated with bentazon than if they were treated with thifensulfuron-methyl or metribuzin. Three weeks after treatment, clomazone (90 g/ha) and diflufenican (50 g/ha), did not cause any crop injury at all. The results indicated an interesting range of active matters which can be applied in pre-emergence, but weed control in post-emergence stays difficult. PMID:17390816

Dewitte, K; Latré, J; Haesaert, G

2006-01-01

379

Assessing Insecticide Hazard to Bumble Bees Foraging on Flowering Weeds in Treated Lawns  

PubMed Central

Maintaining bee-friendly habitats in cities and suburbs can help conserve the vital pollination services of declining bee populations. Despite label precautions not to apply them to blooming plants, neonicotinoids and other residual systemic insecticides may be applied for preventive control of lawn insect pests when spring-flowering weeds are present. Dietary exposure to neonicotinoids adversely affects bees, but the extent of hazard from field usage is controversial. We exposed colonies of the bumble bee Bombus impatiens to turf with blooming white clover that had been treated with clothianidin, a neonicotinoid, or with chlorantraniliprole, the first anthranilic diamide labeled for use on lawns. The sprays were applied at label rate and lightly irrigated. After residues had dried, colonies were confined to forage for six days, and then moved to a non-treated rural site to openly forage and develop. Colonies exposed to clothianidin-treated weedy turf had delayed weight gain and produced no new queens whereas those exposed to chlorantraniliprole-treated plots developed normally compared with controls. Neither bumble bees nor honey bees avoided foraging on treated white clover in open plots. Nectar from clover blooms directly contaminated by spray residues contained 171±44 ppb clothianidin. Notably, neither insecticide adversely impacted bee colonies confined on the treated turf after it had been mown to remove clover blooms present at the time of treatment, and new blooms had formed. Our results validate EPA label precautionary statements not to apply neonicotinoids to blooming nectar-producing plants if bees may visit the treatment area. Whatever systemic hazard through lawn weeds they may pose appears transitory, however, and direct hazard can be mitigated by adhering to label precautions, or if blooms inadvertently are contaminated, by mowing to remove them. Chlorantraniliprole usage on lawns appears non-hazardous to bumble bees.

Larson, Jonathan L.; Redmond, Carl T.; Potter, Daniel A.

2013-01-01

380

Assessing insecticide hazard to bumble bees foraging on flowering weeds in treated lawns.  

PubMed

Maintaining bee-friendly habitats in cities and suburbs can help conserve the vital pollination services of declining bee populations. Despite label precautions not to apply them to blooming plants, neonicotinoids and other residual systemic insecticides may be applied for preventive control of lawn insect pests when spring-flowering weeds are present. Dietary exposure to neonicotinoids adversely affects bees, but the extent of hazard from field usage is controversial. We exposed colonies of the bumble bee Bombus impatiens to turf with blooming white clover that had been treated with clothianidin, a neonicotinoid, or with chlorantraniliprole, the first anthranilic diamide labeled for use on lawns. The sprays were applied at label rate and lightly irrigated. After residues had dried, colonies were confined to forage for six days, and then moved to a non-treated rural site to openly forage and develop. Colonies exposed to clothianidin-treated weedy turf had delayed weight gain and produced no new queens whereas those exposed to chlorantraniliprole-treated plots developed normally compared with controls. Neither bumble bees nor honey bees avoided foraging on treated white clover in open plots. Nectar from clover blooms directly contaminated by spray residues contained 171±44 ppb clothianidin. Notably, neither insecticide adversely impacted bee colonies confined on the treated turf after it had been mown to remove clover blooms present at the time of treatment, and new blooms had formed. Our results validate EPA label precautionary statements not to apply neonicotinoids to blooming nectar-producing plants if bees may visit the treatment area. Whatever systemic hazard through lawn weeds they may pose appears transitory, however, and direct hazard can be mitigated by adhering to label precautions, or if blooms inadvertently are contaminated, by mowing to remove them. Chlorantraniliprole usage on lawns appears non-hazardous to bumble bees. PMID:23776667

Larson, Jonathan L; Redmond, Carl T; Potter, Daniel A

2013-01-01

381

Host Suitability of 32 Common Weeds to Meloidogyne hapla in Organic Soils of Southwestern Quebec  

PubMed Central

Thirty-two weeds commonly found in the organic soils of southwestern Quebec were evaluated for host suitability to a local isolate of the northern root-knot nematode Meloidogyne hapla under greenhouse conditions. Galls were observed on the roots of 21 species. Sixteen of the 21 had a reproduction factor (Pf/Pi = final number of M. hapla eggs and juveniles per initial number of M. hapla juveniles per pot) higher than carrot (Pf/Pi = 0.37), the major host crop in this agricultural area. Tomato cv. Rutgers was also included as a susceptible host and had the highest Pf/Pi value of 13.7. Bidens cernua, B. frondosa, B. vulgata, Erysimum cheiranthoides, Eupatorium maculatum, Matricaria matricarioides, Polygonum scabrum, Thalictrum pubescens, Veronica agrestis, and Sium suave are new host records for M. hapla. Bidens cernua, B. frondosa, B. wulgata, D. carota, M. matricarioides, Pasticana sativa, P. scabrum, S. suave, and Thlaspi arvense sustained moderate to high galling by M. hapla and supported high M. hapla production (12.4 ? Pf/Pi ? 2.9). Capsella bursa-pastoris, Chrysanthemum leucanthemum, Gnaphalium uliginosum, Stellaria media, and Veronica agrestis sustained moderate galling and supported moderate M. hapla reproduction (2.8 ? Pf/Pi ? 0.5). Chenopodium album, C. glaucum, E. cheiranthoides, P. convolvulus, Portulaca oleracea, and Rorippa islandica supported low reproduction (0.25 ? Pf/Pi ? 0.02) and sustained low galling. Galling was observed on Senecio vulgaris but no eggs or juveniles; thus, S. vulgaris may be useful as a trap plant. Eupatorium maculatum, and T. pubescens harbored no distinct galling but supported low to moderate M. hapla reproduction, respectively. Amaranthus retroflexus, Ambrosia artemisiifolia, Echinochloa crusgalli, Erigeron canadensis, Oenothera parviflora, Panicum capillare, Setaria glauca, S. viridis, and Solidago canadensis were nonhosts. Our results demonstrate the importance of adequate weed control in an integrated program for the management of M. hapla in organic soil.

Belair, G.; Benoit, D. L.

1996-01-01

382

Herbicidal effects of extracts and residue incorporation of Datura metel against parthenium weed.  

PubMed

The present study was designed to evaluate the herbicidal activity of Datura metel against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5, 10, 15 and 20% w/v (on a fresh weight basis) concentration of D. metel were tested against the germination and seedling growth of parthenium. Both aqueous and methanol extracts markedly suppressed the germination and seedling growth of parthenium. Generally, the effect of shoot extracts was more pronounced than the effect of root extracts. In foliar spray bioassay, aqueous and methanol shoot extracts of 10% w/v (on dry weight bases) concentrations were sprayed on one-week and two-week-old pot-grown parthenium seedlings. Two subsequent sprays were carried out at five day intervals each. Both the aqueous as well as the methanol extracts significantly suppressed shoot length as well as shoot and root biomass of one-week and two-week-old parthenium plants. In residue incorporation bioassay, crushed shoots of D. metel were incorporated in the soil at 1, 2, ... 5% w/w. Parthenium seeds were sown one week after residue incorporation and plants were harvested 40 days after sowing. Incorporation of 2-5% residues significantly reduced germination by 47-89%. Residues of 4 and 5% concentration significantly suppressed plant biomass by 90 and 97%, respectively. The present study concludes that root and shoots of D. metel contain herbicidal constituents for the management of parthenium weed. PMID:20812130

Javaid, Arshad; Shafique, Sobiya; Shafique, Shazia

2010-09-01

383

National Summit on Strategies to Manage Herbicide-Resistant Weeds. Proceedings of a Workshop. Held in Washington, DC on May 10, 2012.  

National Technical Information Service (NTIS)

Preserving the efficacy of herbicides and of herbicide-resistance technology depends on awareness of the increasing resistance of weeds to herbicides used in agriculture and coordinated action to address the problem by individuals at the farm level and be...

2012-01-01

384

Potential effects of global atmospheric CO2 enrichment on the growth and competitiveness of C3 and C4 weed and crop plants  

SciTech Connect

Research report: Mathematical growth analysis techniques were used to determine the effects of carbon dioxide on the growth and biomass partitioning in corn (zea mays), itchgrass (Rottbiellia exalata concentrations of 350 ppM, 600 ppM, and 1000 ppM were considered. Dry matter production in soybean and velvetleaf was increased significantly by raising the CO2 concentration above 350 ppM. Dry matter production in itchgrass was greatest at 600 ppM; CO2 levels did not affect dry matter production in corn. Weed growth with each plant at the various CO2 concentrations was also measured. CO2 enrichment increased weed growth in weeds planted with soybean and velvetleaf; weeds planted with corn and itchgrass did not experience any significant increase in growth. (18 references, 4 tables)

Patterson, D.T.; Flint, E.P.

1980-01-01

385

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

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. PMID:24612539

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

2014-04-01

386

Cover crops and natural vegetation mulch effect achieved by mechanical management with lateral rotary mower in weed population dynamics in citrus.  

PubMed

The aim of this study was to obtain information on practical weed management in order to reduce the use of herbicides thereby contributing to the sustainable development of citrus crop. The experiment was carried out under field conditions at the experimental area of the Department of Vegetal Production at the College of Agriculture "Luiz de Queiroz," Piracicaba, SP, Brazil, during the season 2002-2003. Influence of mulches produced by four types of vegetations on the dynamic population of weeds in the line of citrus crop (Citrus sinensis (L.) Osbeck) was evaluated. The experimental design was of factorial randomized blocks (4 x 2), where the treatments were: (i) four types of vegetation: Dolichos lablab L., Cajanus cajan (L.) Millsp, Penisetum glaucum (L.) Leeke, and the natural infestation composed basically by Panicum maximum Jacq.; and (ii) two types of fertilization: directed under canopy and broadcast. Mechanical management of the different vegetations was accomplished using a lateral rotary mower, KAMAQ, I model NINJA MAC 260, projected to release the green cut material under crop canopy, forming a mulch layer. The studied parameters were: (i) counting of weeds per m2 in the crop line after 30, 60, 90, 180, and 210 days following the cutting of existing vegetation; (ii) percentage of covered area by weeds; and (iii) some chemical properties of the soil. It was observed that the natural infestation showed a better weed control when compared with the other treatments, and that the broadcast fertilization, regardless of coverage used, presented a lower number of weeds. PMID:15656179

Matheis, Héctor Alonso San Martín; Filho, Ricardo Victoria

2005-01-01

387

Matching the origin of an invasive weed for selection of a herbivore haplotype for a biological control programme.  

PubMed

The Florida Everglades have been invaded by an exotic weed fern, Lygodium microphyllum. Across its native distribution in the Old World tropics from Africa to Australasia it was found to have multiple location-specific haplotypes. Within this distribution, the climbing fern is attacked by a phytophagous mite, Floracarus perrepae, also with multiple haplotypes. The genetic relationship between mite and fern haplotypes was matched by an overarching geographical relationship between the two. Further, mites that occur in the same location as a particular fern haplotype were better able to utilize the fern than mites from more distant locations. From a biological control context, we are able to show that the weed fern in the Everglades most likely originated in northern Queensland, Australia/Papua New Guinea and that the mite from northern Queensland offers the greatest prospect for control. PMID:16367847

Goolsby, John A; DE Barro, Paul J; Makinson, Jeffrey R; Pemberton, Robert W; Hartley, Diana M; Frohlich, Donald R

2006-01-01

388

Poke Weed Mitogen Requires Toll-Like Receptor Ligands for Proliferative Activity in Human and Murine B Lymphocytes  

PubMed Central

Poke weed mitogen (PWM), a lectin purified from Phytolacca americana is frequently used as a B cell-specific stimulus to trigger proliferation and immunoglobulin secretion. In the present study we investigated the mechanisms underlying the B cell stimulatory capacity of PWM. Strikingly, we observed that highly purified PWM preparations failed to induce B cell proliferation. By contrast, commercially available PWM preparations with B cell activity contained Toll-like receptor (TLR) ligands such as TLR2-active lipoproteins, lipopolysaccharide and DNA of bacterial origin. We show that these microbial substances contribute to the stimulatory activity of PWM. Additional experimental data highlight the capacity of PWM to enable B cell activation by immunostimulatory DNA. Based on these findings we propose that the lectin sensitizes B cells for TLR stimulation as described for B cell receptor ligation and that B cell mitogenicity of PWM preparations results from synergistic activity of the poke weed lectin and microbial TLR ligands present in the PWM preparations.

Bekeredjian-Ding, Isabelle; Foermer, Sandra; Kirschning, Carsten J.; Parcina, Marijo; Heeg, Klaus

2012-01-01

389

New strigolactone mimics: structure-activity relationship and mode of action as germinating stimulants for parasitic weeds.  

PubMed

Strigolactones (SLs) are new plant hormones with varies important bio-functions. This Letter deals with germination of seeds of parasitic weeds. Natural SLs have a too complex structure for synthesis. Therefore, there is an active search for SL analogues and mimics with a simpler structure with retention of activity. SL analogues all contain the D-ring connected with an enone moiety through an enol ether unit. A new mechanism for the hydrolysis SL analogues involving bidentate bound water and an ?,?-hydrolase with a Ser-His-Asp catalytic triad has been proposed. Newly discovered SL mimics only have the D-ring with an appropriate leaving group at C-5. A mode of action for SL mimics was proposed for which now supporting evidence is provided. As predicted an extra methyl group at C-4 of the D-ring blocks the germination of seeds of parasitic weeds. PMID:23920440

Zwanenburg, Binne; Nayak, Sandip K; Charnikhova, Tatsiana V; Bouwmeester, Harro J

2013-09-15

390

Gene flow from herbicide-tolerant GM rice and the heterosis of GM rice-weed F2 progeny  

Microsoft Academic Search

Gene flow from genetically modified (GM) crops to non-GM cultivars or weedy relatives may lead to the development of more\\u000a aggressive weeds. We quantified the amount of gene flow from herbicide-tolerant GM rice (Protox GM, derived from the cultivar Dongjin) to three cultivars (Dongjin, Aranghyangchal and Hwaseong) and a weedy rice line. Gene\\u000a flow frequency generally decreased with increasing distance

Young Jin Chun; Dae In Kim; Kee Woong Park; Hyo-Jeong Kim; Soon-Chun Jeong; Ju Hee An; Kang Hyun Cho; Kyoungwhan Back; Hwan Mook Kim; Chang-Gi Kim

2011-01-01

391

A new insight into arable weed adaptive evolution: mutations endowing herbicide resistance also affect germination dynamics and seedling emergence  

PubMed Central

Background and Aims Selective pressures exerted by agriculture on populations of arable weeds foster the evolution of adaptive traits. Germination and emergence dynamics and herbicide resistance are key adaptive traits. Herbicide resistance alleles can have pleiotropic effects on a weed's life cycle. This study investigated the pleiotropic effects of three acetyl-coenzyme A carboxylase (ACCase) alleles endowing herbicide resistance on the seed-to-plant part of the life cycle of the grass weed Alopecurus myosuroides. Methods In each of two series of experiments, A. myosuroides populations with homogenized genetic backgrounds and segregating for Leu1781, Asn2041 or Gly2078 ACCase mutations which arose independently were used to compare germination dynamics, survival in the soil and seedling pre-emergence growth among seeds containing wild-type, heterozygous and homozygous mutant ACCase embryos. Key Results Asn2041 ACCase caused no significant effects. Gly2078 ACCase major effects were a co-dominant acceleration in seed germination (1·25- and 1·10-fold decrease in the time to reach 50 % germination (T50) for homozygous and heterozygous mutant embryos, respectively). Segregation distortion against homozygous mutant embryos or a co-dominant increase in fatal germination was observed in one series of experiments. Leu1781 ACCase major effects were a co-dominant delay in seed germination (1·41- and 1·22-fold increase in T50 for homozygous and heterozygous mutant embryos, respectively) associated with a substantial co-dominant decrease in fatal germination. Conclusions Under current agricultural systems, plants carrying Leu1781 or Gly2078 ACCase have a fitness advantage conferred by herbicide resistance that is enhanced or counterbalanced, respectively, by direct pleiotropic effects on the plant phenology. Pleiotropic effects associated with mutations endowing herbicide resistance undoubtedly play a significant role in the evolutionary dynamics of herbicide resistance in weed populations. Mutant ACCase alleles should also prove useful to investigate the role played by seed storage lipids in the control of seed dormancy and germination.

Delye, Christophe; Menchari, Yosra; Michel, Severine; Cadet, Emilie; Le Corre, Valerie

2013-01-01

392

Effects of tractor weight, wheel placement and depth of ploughing on the infestation of perennial weeds in organically farmed cereals  

Microsoft Academic Search

To ensure optimum conditions for organic cereal growing, it is important to minimize both compaction and soil inversion depth. The relative effects of using light versus heavier tractors, shallow versus deeper ploughing and on-land versus in-furrow wheel placement during ploughing were investigated in three-year organic rotations dominated by cereals with naturally infested stands of perennial weeds. The second part of

Lars Olav Brandsæter; Anne Kjersti Bakken; Kjell Mangerud; Hugh Riley; Ragnar Eltun; Haldor Fykse

2011-01-01

393

Tillage and herbicides impact on weed control and wheat yield under rice–wheat cropping system in Northwestern Pakistan  

Microsoft Academic Search

Wheat (Triticum aestivum L.) production is low in rice (Oryza sativa L.)–wheat cropping system in the low-precipitation zone of Dera Ismail Khan, Pakistan. A 2 years field experiment was conducted during 2007–2009 to evaluate the effect of tillage systems and herbicides on weed control efficiency (WCE) and wheat yield under rice–wheat cropping system. Three tillage systems, zero tillage (ZT), reduced

Khalid Usman; Shad Khan Khalil; Amir Zaman Khan; Iftikhar Hussain Khalil; Muhammad Azim Khan; Amanullah

2010-01-01

394

Weed control in flooded rice with various herbicide combinations in the Southern Guinea Savanna zone of Nigeria  

Microsoft Academic Search

Field trials were conducted during the 1990 and 1991 wet seasons at Badeggi to assess the efficacy of various herbicide combinations for post?emergence and pre?emergence control of a weed flora dominated by Digltaria debilis (Desf.) Willd., Leptochloa caerulescens Steud., Ludwigia spp., Sphenoclea zeylanica Gaertn. and Cyperus difformis L. in direct?seeded and transplanted lowland rice cv. Faro 29. In 1990 post?emergence

P. O. Imeokparia

1994-01-01

395

Nitrogen Fertility and Weed Management Critical for Continuous No-Till Wheat in the Pacific Northwest 1  

Microsoft Academic Search

No-till cropping is an option for growers needing to reduce soil erosion in the Palouse annual-cropped region of the Pacific Northwest, which is well suited for wheat production. A 6-yr field study was conducted to determine optimum levels of fertilizer and herbicide inputs in a no-till continuous wheat crop production system. Three levels of nitrogen (N) and two weed management

FRANK L. YOUNG; MARK E. THORNE; DOUGLAS L. YOUNG

2006-01-01

396

Weed management in dry-seeded rice ( Oryza sativa) cultivated in the furrow-irrigated raised-bed planting system  

Microsoft Academic Search

Dry seeding of rice (Oryza sativa L.) in the furrow-irrigated raised-bed planting system (FIRBS) represents a major shift in the production practices for attaining optimal water productivity in the rice–wheat system in the Indo-Gangetic Plains of South Asia. Information on weed management in dry-seeded rice in the FIRBS is lacking. Two experiments were conducted for 2 years, with an objective

Samar Singh; Lav Bhushan; J. K. Ladha; R. K. Gupta; A. N. Rao; B. Sivaprasad

2006-01-01

397

Fluazifop-butyl causes membrane peroxidation in the herbicide-susceptible broad leaf weed bristly starbur ( Acanthospermum hispidum)  

Microsoft Academic Search

In order to clarify the action mechanism of fluazifop-butyl, an aryloxyphenoxypropionate (AOPP) herbicide in bristly starbur (Acanthospermum hispidum DC.), a unique fluazifop-butyl-susceptible broad-leaved weed, ethylene evolution and membrane lipid peroxidation in the plant seedlings were investigated. Foliar application of fluazifop-P-butyl induced ethylene evolution only from bristly starbur, but not from oat (Avena sativa L.), another fluazifop-butyl-susceptible species, and two tolerant

Xiao-Yong Luo; Yukari Sunohara; Hiroshi Matsumoto

2004-01-01

398

Butenolide from plant-derived smoke functions as a strigolactone analogue: Evidence from parasitic weed seed germination  

Microsoft Academic Search

The main germination active compound in smoke, 3-methyl-2H-furo[2,3-c]pyran-2-one (butenolide), has structural similarities with strigolactones that function as germination stimulants for root parasitic plants such as Orobanche spp. and Striga spp. (Scrophulariaceae). Consequently, we tested whether butenolide also functions as a germination stimulant for parasitic weeds. Butenolide stimulated germination of both Orobanche minor and Striga hermonthica to similar levels as the

M. I. Daws; H. W. Pritchard; J. Van Staden

2008-01-01

399

Cadmium and lead residues in field-collected red swamp crayfish (Procambarus clarkii) and uptake by alligator weed, Alternanthera philoxiroides  

SciTech Connect

The whole-body residues of Cd and Pb in the tissues of Louisiana swamp crayfish (Procambarus clarkii) were determined by flame AAS technique. Test animals were collected from roadside ditches alongside major highways. The water and soil samples were also collected from the same sites. The mean Cd and Pb concentrations in crayfish tissues were 0.46 and 0.07, respectively. The levels of Cd and Pb in the water were 0.09 and 0.04; and in soil were 2.85 and 0.87 mg/1, respectively. The concentration of cadmium was 32 and Pb 12 times more than in the water. The bioaccumulation factors (BF) for Cd and Pb in crayfish tissues were 5.1 and 1.7, respectively. Alligator weed (Alternanthera philoxiroides) plants were exposed to 0.5 mg/1 Cd-chloride or Pb-nitrate solutions for 3 wk period, thrice. The mean Pb accumulation in roots was 1.31 mg/1, followed by stem (0.078 mg/1), but Cd only accumulated in root (0.83 mg/1). The BF for Pb and Cd in plant tissues were 14.8 and 16.6, respectively. The uptake of metals was time-dependent. These data suggest that although there is no biomagnification of Cd and Pb from alligator weed to crayfish, both metals readily accumulate in field-collected crayfish and laboratory-exposed alligator weed.

Naqvi, S.M.; Howell, R.D.; Sholas, M. (Southern Univ., Baton Rouge, LA (United States). Dept. of Biological Sciences and Health Research Center)

1993-01-01

400

[Allelopathy of aqueous extract from Ligularia virgaurea, a dominant weed in psychro-grassland, on pasture plants].  

PubMed

Ligularia virgaurea is a noxious weed widely distributed in the alpine grassland of east Qinghai-Tibet Plateau of China. This paper studied the allelopathy of its aqueous extract on the pasture plants Festuca sinensis, Bromus magnus, Elymus nutans, Poa annua, and F. ovina in the region. The mean response index (RI) values of the pasture plants were calculated, and used to quantitatively assess the allelopathic sensitivity of the receptors at three levels, i. e., growth items, development stages, and species. Corresponding values of the weed were also treated in similar way to assess the allelopathic potential of the donor. The results showed that the allelopathic sensitivity was in the order of P. annua > B. magnus > F. sinensis > F. ovina > E. nutans. Both the seed germination and the seedling growth of test pasture plants were inhibited at species level, suggesting that rain eluviation was one of the means by which the weed released allelochemicals. The aqueous extracts from L. virgaurea root and leaf had a significant inhibitory effect at species level, and the effect of root extract was stronger than that of leaf extract, suggesting the competition among species on the underground resources in natural grassland. Allelopathy played an important role in L. virgaurea invasion, and might be responsible to the formation of mono-dominant community and the degeneration of grassland. PMID:16883813

Ma, Ruijun; Wang, Mingli; Zhao, Kun; Guo, Shoujun; Zhao, Qingfang; Sun, Kun

2006-05-01

401

Detection of stress factors in crop and weed species using hyperspectral remote sensing reflectance  

NASA Astrophysics Data System (ADS)

The primary objective of this work was to determine if stress factors such as moisture stress or herbicide injury stress limit the ability to distinguish between weeds and crops using remotely sensed data. Additional objectives included using hyperspectral reflectance data to measure moisture content within a species, and to measure crop injury in response to drift rates of non-selective herbicides. Moisture stress did not reduce the ability to discriminate between species. Regardless of analysis technique, the trend was that as moisture stress increased, so too did the ability to distinguish between species. Signature amplitudes (SA) of the top 5 bands, discrete wavelet transforms (DWT), and multiple indices were promising analysis techniques. Discriminant models created from one year's data set and validated on additional data sets provided, on average, approximately 80% accurate classification among weeds and crop. This suggests that these models are relatively robust and could potentially be used across environmental conditions in field scenarios. Distinguishing between leaves grown at high-moisture stress and no-stress was met with limited success, primarily because there was substantial variation among samples within the treatments. Leaf water potential (LWP) was measured, and these were classified into three categories using indices. Classification accuracies were as high as 68%. The 10 bands most highly correlated to LWP were selected; however, there were no obvious trends or patterns in these top 10 bands with respect to time, species or moisture level, suggesting that LWP is an elusive parameter to quantify spectrally. In order to address herbicide injury stress and its impact on species discrimination, discriminant models were created from combinations of multiple indices. The model created from the second experimental run's data set and validated on the first experimental run's data provided an average of 97% correct classification of soybean and an overall average classification accuracy of 65% for all species. This suggests that these models are relatively robust and could potentially be used across a wide range of herbicide applications in field scenarios. From the pooled data set, a single discriminant model was created with multiple indices that discriminated soybean from weeds 88%, on average, regardless of herbicide, rate or species. Several analysis techniques including multiple indices, signature amplitude with spectral bands as features, and wavelet analysis were employed to distinguish between herbicide-treated and nontreated plants. Classification accuracy using signature amplitude (SA) analysis of paraquat injury on soybean was better than 75% for both 1/2 and 1/8X rates at 1, 4, and 7 DAA. Classification accuracy of paraquat injury on corn was better than 72% for the 1/2X rate at 1, 4, and 7 DAA. These data suggest that hyperspectral reflectance may be used to distinguish between healthy plants and injured plants to which herbicides have been applied; however, the classification accuracies remained at 75% or higher only when the higher rates of herbicide were applied. (Abstract shortened by UMI.)

Henry, William Brien

402

Differential susceptibility to glyphosate among the Conyza weed species in Spain.  

PubMed

Greenhouse and laboratory experiments were conducted to investigate differences in glyphosate susceptibility among three species of the genus Conyza introduced as weeds in Spain: tall fleabane (Conyza sumatrensis), hairy fleabane (Conyza bonariensis), and horseweed (Conyza canadensis). Plant material was obtained from seeds collected in weed populations growing in olive groves and citrus orchards in southern Spain, with no previous history of glyphosate application. Dose-response curves displayed ED(50) values of 2.9, 15.7, and 34.9 g ai ha(-1), respectively, for C. sumatrensis, C. bonariensis, and C. canadensis plants at the rosette stage (6-8 leaves). Significant differences were found among the three species in the glyphosate retention on leaves as well as the leaf contact angle. The species order according to glyphosate retention was C. sumatrensis > C. bonariensis > C. canadensis, while the mean contact angles of glyphosate droplets were 59.2, 65.5, and 72.9 degrees , respectively. There were no significant differences among species in the absorption of [(14)C]glyphosate (ranged from 37.4% for C. canadensis to 52.4% for C. sumatrensis), but the order among species was the same as glyphosate retention. The amount of radioactivity translocated from treated leaves was lower in C. canadensis as compared to the other two species (C. sumatrensis > C. bonariensis > C. canadensis). Combined, all of the studied parameters identified differential susceptibility to glyphosate among the Conyza species. Each species accumulated shikimate in leaf tissues following application of glyphosate at 200 g ai ha(-1). However, C. canadensis exhibited lower shikimate levels than the other two species at 168 h after herbicide application. For hairy fleabane, a greenhouse study explored its susceptibility to glyphosate at three developmental stages: rosette, bolting (stem height, 10-15 cm), and flowering. The ED(50) was lower at the rosette stage (15.7 g ai ha(-1)) as compared to bolting (86.6 g ai ha(-1)), with the highest ED(50) values occurring at flowering (117.5 g ai ha(-1)); plants at the earlier developmental stage retained more glyphosate. These results agree with field observations that plants at early developmental stages are more sensitive to glyphosate. PMID:20225860

González-Torralva, Fidel; Cruz-Hipolito, Hugo; Bastida, Fernando; Mülleder, Norbert; Smeda, Reid J; De Prado, Rafael

2010-04-14

403

Weeds as a source of plant growth promoting rhizobacteria in agricultural soils.  

PubMed

The influence of plant growth promoting (PGP) activity of bacterial communities recovered from each of six weed species (barnyard grass (Echinochloa crusfalli (L.) Beauv.), corn spurrey (Spergula arvensis L.), goldenrod (Sonchus sp.), Italian ryegrass (Lolium multiflorum L.), lamb's-quarters (Chenopodium album L.), and quack grass (Agropyron repens (L.) Beauv.)) was examined in relation to the effect it had on the growth of the potato cultivar Russet Burbank. Bacterial species composition and community structure were compared, species-abundance relationships were determined, and those members conferring positive benefits for potato growth and development were identified. Of the genera identified, Bacillus, Arthrobacter, Stenotrophomonas, Acinetobacter, and Pseudomonas were the most common, and Stenotrophomonas maltophilia was the most frequent species recovered across all sources. Significantly higher population densities were found in the root zones of quack grass, compared with Italian ryegrass and lamb's-quarters. There were no significant differences in species richness among the root zones; however, evenness indices (species distribution) were significantly lower in corn spurrey (P = 0.05). Significantly higher diversity indices (Hill-1 and Hill-2 numbers) (P = 0.05) were found in the root zone soil communities of potato and goldenrod, indicating a decrease in the proportional abundance of common and very abundant species, respectively, while in barnyard grass, corn spurrey, and Italian ryegrass the reverse was the case. In both years of the study, Italian ryegrass and corn spurrey were consistently better sources of PGP rhizobacteria for potatoes, significantly (P < 0.001) increasing the mean wet weight of shoots and roots in in vitro bacterization studies. Barnyard grass was a consistently poor source of such isolates. Species-abundance measures of root zone bacterial biodiversity were not found, in this instance, to be a particularly good predictor of the presence or absence of PGP rhizobacteria. We consider that the study of complementary crops and soil-conditioning treatments should not preclude the examination of weed species as possible beneficials, as alterations in rhizobacterial biodiversity and functional versatility can influence the numbers and types of PGP bacterial strains, and consequently may serve to improve soil quality. PMID:11766050

Sturz, A V; Matheson, B G; Arsenault, W; Kimpinski, J; Christie, B R

2001-11-01

404

Annual Glyphosate Treatments Alter Growth of Unaffected Bentgrass (Agrostis) Weeds and Plant Community Composition  

PubMed Central

Herbicide resistance is becoming more common in weed ecotypes and crop species including turfgrasses, but current gaps in knowledge limit predictive ecological risk assessments and risk management plans. This project examined the effect of annual glyphosate applications on the vegetative growth and reproductive potential of two weedy bentgrasses, creeping bentgrass (CB) and redtop (RT), where the glyphosate resistance (GR) trait was mimicked by covering the bentgrass plants during glyphosate application. Five field plots were studied in habitats commonly inhabited by weedy bentgrasses including an agricultural hayfield, natural meadow, and wasteland. Results showed that annual glyphosate treatment improved bentgrass survivorship, vegetative growth, and reproductive potential compared with bentgrass in unsprayed subplots. In the second year of growth, RT plants had an 86-fold increase in flower number in glyphosate-treated subplots versus controls, while CB plants had a 20-fold increase. At the end of the three year study, plant community composition had changed in glyphosate-treated subplots in hayfield and meadow plots compared to controls. Soils in subplots receiving glyphosate had higher nitrate concentrations than controls. This is the first study to mimic the GR trait in bentgrass plants with the goal of quantifying bentgrass response to glyphosate selection pressure and understanding the impacts on surrounding plant communities.

Ahrens, Collin W.; Auer, Carol A.

2012-01-01

405

Genetic variation in the response of the weed Ruellia nudiflora (Acanthaceae) to arbuscular mycorrhizal fungi.  

PubMed

The main goal of this work was to test for plant genetic variation in the phenotypic plasticity response of the weed Ruellia nudiflora to arbuscular mycorrhizal (AM) fungi inoculation. We collected plants in the field, kept them under homogeneous conditions inside a nursery, and then collected seeds from these parent plants to generate five inbred lines (i.e., genetic families). Half of the plants of each inbred line were inoculated with AM fungi while the other half were not (controls); a fully crossed experimental design was then used to test for the effects of treatment (with or without AM fungi inoculation) and inbred line (genetic family). For each plant, we recorded the number of leaves produced and the number of days it survived during a 2-month period. Results showed a strong positive treatment effect (plastic response to AM fungi inoculation) for leaf production and survival. Moreover, in terms of survival, the treatment effect differed between genetic families (significant genetic family by treatment interaction). These findings indicate that the positive effect of AM fungi on plant survival (and potentially also growth) differs across plant genotypes and that such condition may contribute to R. nudiflora's capacity to colonize new environments. PMID:19862559

Ramos-Zapata, José Alberto; Campos-Navarrete, María José; Parra-Tabla, Víctor; Abdala-Roberts, Luis; Navarro-Alberto, Jorge

2010-04-01

406

Effect of increased UV-B on weeds and big worms in a farmland ecological system  

NASA Astrophysics Data System (ADS)

Since the 1970's stratospheric zone attenuation liable for surface UV radiation enhancement has been among the ever-increasing concerns of global climatologists. In recent years, numerous efforts have been undertaken at home and abroad to investigate the effect of enhanced surface UV-B on crops' growth, development and yield formation, achieving a lot of significant fruits and concurrently on field ecosystems. As we know, most of the experiments in the past were conducted in laboratories, including a short-term response on an individual-plant basis. This condition differs consipicuously from yield experiments at the level of an ecosystem with regard to its long-range response. Specifically the degree to which the UV radiation influences non-crop species, which leads to the distortion of the response to UV-B enhancement of crop's population and its ecosystem. As a result, it is necessary to carry out long-range field experiments at an ecosystem's level. This paper aims at the impacts of intensified UV-B upon weeds and large soil worms (i.e., microanimals) in an ecosystem of growing wheat, corn (maize) and spinach together with preliminary investigation of the mechanisms.

Zheng, Youfei; Gao, Wei; Wang, Chuanhai; Xiao, Wei; Zhang, Ronggang

2003-11-01

407

Tank mixture additives approach to improve efficiency of bentazon against broadleaf weeds in peas.  

PubMed

Efficiency of different tank-mixed additives with bentazon at half rate was investigated on (Malva parviflora) and other broad leaf weeds compared with bentazon at the full recommended rate without additives in peas in open field. All the tested additives enhanced the efficiency of bentazon at the half rate. Nonyl phenol and toximol S proved to be the most effective additives in comparison with the full rate treatment. The tested treatments did not show any significant effect on chlorophyll content and soil microorganisms. Bentazon residues were determined in certain treatments to investigate the effect of the tested additives on bentazon deposition. Samples were extracted using QuEChERS method and residues were determined using LC-MS/MS. Residues after 24 hours in the half rate treatment reached 4 times lower than the Maximum Residues Limit (MRL) (0.11 mg kg(-1)), compared to the full rate treatment (0.51 mg kg(-1)), that was slightly above the MRL. PMID:22424063

Balah, Mohamed A; Hanafi, Ahmad; Ghani, Sherif B Abdel

2012-01-01

408

Phytotoxic Antibiotic Sulfadimethoxine Elicits a Complex Hormetic Response in the Weed Lythrum Salicaria L  

PubMed Central

In order to evaluate the hormetic response of the weed Lythrum salicaria to drug exposure we investigated the effects of the antibiotic Sulfadimethoxine by growing Lythrum plants for 28 days on culture media containing different drug concentrations (between 0.005 and 50 mg.L?1). The antibiotic was absorbed by plants and can be found in plant tissue. The plant response was organ-dependent: roots, cotyledons and cotyledon petioles, were always affected by a toxic effect, whilst internodes and leaves length, showed a variable dose-depending response, with an increased growth at the lower drug concentrations and toxic effects at the higher ones. This variable response was probably dependant on different levels of local contamination resulting from a balance between accumulation rate and drug dilution in the increasing plant biomass. As a consequence, drug toxicity or hormetic response varied according to concentration and were different in each of the examined plant organ/tissue. Thus, even if hormesis can be considered a general plant response, each plant organ/tissue responds differently, depending on the local drug concentration and exposure time.

Migliore, Luciana; Rotini, Alice; Cerioli, Nadia L.; Cozzolino, Salvatore; Fiori, Maurizio

2010-01-01

409

A seasonal, density-dependent model for the management of an invasive weed.  

PubMed

The population effects of harvest depend on complex interactions between density dependence, seasonality, stage structure, and management timing. Here we present a periodic nonlinear matrix population model that incorporates seasonal density dependence with stage-selective and seasonally selective harvest. To this model, we apply newly developed perturbation analyses to determine how population densities respond to changes in harvest and demographic parameters. We use the model to examine the effects of popular control strategies and demographic perturbations on the invasive weed garlic mustard (Alliaria petiolata). We find that seasonality is a major factor in harvest outcomes, because population dynamics may depend significantly on both the season of management and the season of observation. Strategies that reduce densities in one season can drive increases in another, with strategies giving positive sensitivities of density in the target seasons leading to compensatory effects that invasive species managers should avoid. Conversely, demographic parameters to which density is very elastic (e.g., seeding survival, second-year rosette spring survival, and the flowering to fruiting adult transition for maximum summer densities) may indicate promising management targets. PMID:24555315

Shyu, Esther; Pardini, Eleanor A; Knight, Tiffany M; Caswell, Hal

2013-12-01

410

Green synthesis of silver nanoparticles using cellulose extracted from an aquatic weed; water hyacinth.  

PubMed

As part of the desire to save the environment through "green" chemistry practices, we herein report an environmentally benign synthesis of silver nanoparticles (Ag-NPs) using cellulose extracted from an environmentally problematic aquatic weed, water hyacinth (WH), as both reducing and capping agent in an aqueous medium. By varying the pH of the solution and reaction time, the temporal evolutions of the optical and morphological properties of the as-synthesised Ag-NPs were investigated. The as-synthesised cellulose capped silver nanoparticles (C-Ag-NPs) were characterised using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The maximum surface plasmon resonance (SPR) peak decreased as the pH increased indicating that an increase in the pH of the solution favoured the formation of smaller particles. In addition, instantaneous change in the colour of the solution from colourless to brown within 5 min at pH 11 showed that the rate of reduction is faster at this pH compared to those at lower pH. The TEM micrographs showed that the materials are small, highly monodispersed and spherical in shape. The average particle mean diameters were calculated to be 5.69±5.89 nm, 4.53±1.36 nm and 2.68±0.69 nm nm at pH 4, 8 and 11 respectively. The HRTEM confirmed the crystallinity of the material while the FTIR spectra confirmed the capping of the as-synthesised Ag-NPs by the cellulose. It has been shown therefore that based on this synthetic method, this aquatic plant can be used to the advantage of mankind. PMID:23987347

Mochochoko, Tanki; Oluwafemi, Oluwatobi S; Jumbam, Denis N; Songca, Sandile P

2013-10-15

411

Potential of olive mill waste and compost as biobased pesticides against weeds, fungi, and nematodes.  

PubMed

The phytotoxic and antimicrobial properties of olive mill wastes have been widely investigated and demonstrated over the past decade. However, their potential utilization as biodegradable pesticides against plant pathogens is still poorly understood. In this study, a series of laboratory bioassays was designed to test the inhibitory effects of sterile water extracts of two-phase olive mill waste (TPOMW) and TPOMW composts with different degrees of stabilization on several different plant pathogens. Fungicidal properties of TPOMW extracts, assayed in a microwell assay format, showed that the growth of Phytophthora capsici was consistently and strongly inhibited by all TPOMW extracts diluted 1:10 (w:v). In contrast, suppression of Pythium ultimum and Botrytis cinerea by the extracts was not as strong and depended on the specific TPOMW sample. Mature compost inhibited P. capsici and B. cinerea at dilutions as great as 1:50, w:v. Neither TPOMW nor TPOMW compost extracts were able to inhibit the growth of the basidiomycete root rot agent Rhizoctonia solani. In addition, studies were conducted on the allelopathic effects of TPOMW extracts on seed germination of four highly invasive and globally distributed weeds (Amaranthus retroflexus, Solanum nigrum, Chenopodium album and Sorghum halepense). Both the TPOMW and immature TPOMW compost extracts substantially inhibited germination of A. retroflexus and S. nigrum, whereas mature composts extracts only partially reduced the germination of S. nigrum. Finally, TPOMW extracts strongly inhibited egg hatch and second-stage juvenile (J2) motility of the root-knot nematode Meloidogyne incognita. However, only higher concentrations of stage-one and stage-two TPOMW compost extracts exerted a suppressive effect on both J2 motility and on egg hatch. The study shows the high potential of naturally occurring chemicals present in TPOMW and TPOMW composts that should be further investigated as bio-pesticides for their use in sustainable agricultural systems. PMID:18471866

Cayuela, M L; Millner, P D; Meyer, S L F; Roig, A

2008-07-25

412

The assessment of phytoremediation potential of invasive weed Amaranthus spinosus L.  

PubMed

Presently the environment is heavily polluted by various toxic metals, which creates danger for all living beings. Heavy metals are toxic above certain threshold levels. Phytoremediation is an emerging technology which is quite a novel technique of cleaning polluted sites through the use of plants. Phytoremediation methods are comparatively cheap and ecologically advantageous, compared to conventional and physicochemical methods like precipitation, evaporation and chemical reduction. In this respect, plants can be compared to solar-driven pumps capable of extracting and concentrating certain elements from their environment. Amaranthus spinosus, an invasive weed seen on road sides and bare land belonging to the family Amaranthaceae, was selected for the present study. A greenhouse experiment was conducted and consisted of a range-finding test and definitive test for various concentrations of heavy metals Cu, Zn, Cr, Pb and Cd. Plants were grown in soil treated with different concentration of metals depending upon the threshold level. The bio-organics of the plant such as soluble sugar, protein, lipid, phenol, amino acid and photosynthetic pigments were estimated after 30 days of treatment. The bio-organics showed profound variation in response to accumulation of heavy metals. Accumulation of Cu, Pb and Cd was high in the roots followed by stem and leaves and that of Zn and Cr remained high in aerial parts. A steady increase was noticed in the bioaccumulation of copper, zinc and cadmium on enhancing the concentration of the corresponding metal in the soil. The bioconcentration factor and translocation factor were above unity in most of the treatments and increased as the concentration of treatment increased which indicated that A. spinosus is a potential agent for heavy metal accumulation and translocation. PMID:22528651

Chinmayee, M Devi; Mahesh, B; Pradesh, S; Mini, I; Swapna, T S

2012-07-01

413

Complete Chloroplast Genome Sequence of a Major Invasive Species, Crofton Weed (Ageratina adenophora)  

PubMed Central

Background Crofton weed (Ageratina adenophora) is one of the most hazardous invasive plant species, which causes serious economic losses and environmental damages worldwide. However, the sequence resource and genome information of A. adenophora are rather limited, making phylogenetic identification and evolutionary studies very difficult. Here, we report the complete sequence of the A. adenophora chloroplast (cp) genome based on Illumina sequencing. Methodology/Principal Findings The A. adenophora cp genome is 150, 689 bp in length including a small single-copy (SSC) region of 18, 358 bp and a large single-copy (LSC) region of 84, 815 bp separated by a pair of inverted repeats (IRs) of 23, 755 bp. The genome contains 130 unique genes and 18 duplicated in the IR regions, with the gene content and organization similar to other Asteraceae cp genomes. Comparative analysis identified five DNA regions (ndhD-ccsA, psbI-trnS, ndhF-ycf1, ndhI-ndhG and atpA-trnR) containing parsimony-informative characters higher than 2%, which may be potential informative markers for barcoding and phylogenetic analysis. Repeat structure, codon usage and contraction of the IR were also investigated to reveal the pattern of evolution. Phylogenetic analysis demonstrated a sister relationship between A. adenophora and Guizotia abyssinica and supported a monophyly of the Asterales. Conclusion We have assembled and analyzed the chloroplast genome of A. adenophora in this study, which was the first sequenced plastome in the Eupatorieae tribe. The complete chloroplast genome information is useful for plant phylogenetic and evolutionary studies within this invasive species and also within the Asteraceae family.

Zhang, Yingxin; Du, Xianghong; Wang, Le; Biradar, Siddanagouda S.; Tan, Xiufang; Wan, Fanghao; Weining, Song

2012-01-01

414

An easy and rapid method using microscopy to determine herbicide effects in Poaceae weed species.  

PubMed

A new, easy, rapid and relatively inexpensive method using microscopy has been developed for the detection of herbicide effects in leaves of grass weed species displaying no visual signs of damage. The method has potential to be used as a tool to indicate future death of grass species due to herbicide exposure by observing phytochemical effects, i.e. early-warning effects. In the present study, Apera spica-venti (L.) Beauv., Bromus hordeaceus L., Alopecurus myosuroides Huds., Lolium perenne L. and Poa annua L. were exposed to lethal rates of four herbicides with different mode of action. The herbicides investigated were the thiocarbamate: prosulfocarb, the sulfonylurea: iodosulfuron, the aryloxyphenoxypropionate: fenoxaprop-P-ethyl and the organophosphate glyphosate. Autofluorescence of leaves was studied under a microscope using ultraviolet and blue light. The fluorescence of leaves treated to enhance flavonoids was also examined. To confirm the results, microspectrofluorometry was performed. Effects indicating future death of the grasses were observed in visually healthy leaves following treatment with prosulfocarb, glyphosate and iodosulfuron. No changes were detected following treatment with fenoxaprop-P-ethyl. After exposure to glyphosate or iodosulfuron, changes in the content of flavonoids and other compounds with a conjugation system and rigid structure and a decrease in the content of chlorophyll were detected in the leaves. Prosulfocarb treatment resulted in changes in the content of flavonoids and other compounds with a conjugation system and rigid structure and an increase in the content of chlorophyll in the leaves. The results obtained from microspectrofluorometry indicated that exposure to prosulfocarb caused a reduction in the flavonoids quercetin, naringenin and/or naringin. PMID:16628541

Hjorth, Maibritt; Mondolot, Laurence; Buatois, Bruno; Andary, Claude; Rapior, Sylvie; Kudsk, Per; Mathiassen, Solvejg K; Ravn, Helle W

2006-06-01

415

Prevalence of sensitization to weed pollens of Humulus scandens, Artemisia vulgaris, and Ambrosia artemisiifolia in northern China  

PubMed Central

Objective: Weed pollens are common sources of allergens worldwide. The prevalence of weed pollen sensitization is not yet fully known in China. The purpose of this study was to investigate the prevalence of sensitization to weed allergens from Artemisia, Ambrosia, and Humulus in northern China. Methods: A total of 1 144 subjects (aged from 5 to 68 years) visiting our clinic from June to October 2011 underwent intradermal testing using a panel of 25 allergen sources. Subjects with positive skin responses to any pollen were further tested for their serum concentrations of IgE antibodies against Artemisia vulgaris, Ambrosia artemisiifolia, and Humulus scandens, and against the purified allergens, Art v 1 and Amb a 1. Results: Of 1 144 subjects, 170 had positive intradermal reactions to pollen and 144 donated serum for IgE testing. The prevalence of positive intradermal responses to pollens of Artemisia sieversiana, Artemisia annua, A. artemisiifolia, and H. scandens was 11.0%, 10.2%, 3.7%, and 6.6%, respectively. Among the intradermal positive subjects, the prevalence of specific IgE antigens to A. vulgaris was 58.3%, to A. artemisiifolia 14.7%, and to H. scandens 41.0%. The prevalence of specific IgE antigens to the allergen Art v 1 was 46.9%, and to Amb a 1 was 11.2%. The correlation between the presence of IgE antibodies specific to A. vulgaris and to the Art v 1 antigen was very high. Subjects with A. artemisiifolia specific IgE also had A. vulgaris specific IgE, but with relatively high levels of A. vulgaris IgE antibodies. There were no correlations between the presence of IgE antibodies to H. scandens and A. vulgaris or to H. scandens and A. artemisiifolia. Conclusions: The intradermal prevalence of weed pollen sensitization among allergic subjects in northern China is about 13.5%. Correlations of specific IgE antibodies suggest that pollen allergens from Artemisia and Humulus are independent sources for primary sensitization.

Hao, Guo-dong; Zheng, Yi-wu; Gjesing, Birgitte; Kong, Xing-ai; Wang, Jing-yuan; Song, Zhi-jing; Lai, Xu-xin; Zhong, Nan-shan; Spangfort, Michael D.

2013-01-01

416

Prevalence of sensitization to weed pollens of Humulus scandens, Artemisia vulgaris, and Ambrosia artemisiifolia in northern China.  

PubMed

Objective: Weed pollens are common sources of allergens worldwide. The prevalence of weed pollen sensitization is not yet fully known in China. The purpose of this study was to investigate the prevalence of sensitization to weed allergens from Artemisia, Ambrosia, and Humulus in northern China. Methods: A total of 1144 subjects (aged from 5 to 68 years) visiting our clinic from June to October 2011 underwent intradermal testing using a panel of 25 allergen sources. Subjects with positive skin responses to any pollen were further tested for their serum concentrations of IgE antibodies against Artemisia vulgaris, Ambrosia artemisiifolia, and Humulus scandens, and against the purified allergens, Art v 1 and Amb a 1. Results: Of 1144 subjects, 170 had positive intradermal reactions to pollen and 144 donated serum for IgE testing. The prevalence of positive intradermal responses to pollens of Artemisia sieversiana, Artemisia annua, A. artemisiifolia, and H. scandens was 11.0%, 10.2%, 3.7%, and 6.6%, respectively. Among the intradermal positive subjects, the prevalence of specific IgE antigens to A. vulgaris was 58.3%, to A. artemisiifolia 14.7%, and to H. scandens 41.0%. The prevalence of specific IgE antigens to the allergen Art v 1 was 46.9%, and to Amb a 1 was 11.2%. The correlation between the presence of IgE antibodies specific to A. vulgaris and to the Art v 1 antigen was very high. Subjects with A. artemisiifolia specific IgE also had A. vulgaris specific IgE, but with relatively high levels of A. vulgaris IgE antibodies. There were no correlations between the presence of IgE antibodies to H. scandens and A. vulgaris or to H. scandens and A. artemisiifolia. Conclusions: The intradermal prevalence of weed pollen sensitization among allergic subjects in northern China is about 13.5%. Correlations of specific IgE antibodies suggest that pollen allergens from Artemisia and Humulus are independent sources for primary sensitization. PMID:23463767

Hao, Guo-dong; Zheng, Yi-wu; Gjesing, Birgitte; Kong, Xing-ai; Wang, Jing-yuan; Song, Zhi-jing; Lai, Xu-xin; Zhong, Nan-shan; Spangfort, Michael D

2013-03-01

417

Superfund record of decision amendment (EPA Region 9): J. H. Baxter and Company, Weed, CA, March 27, 1998  

SciTech Connect

This decision document presents the US Environmental Protection Agency`s (EPA) revised selected remedial actions for certain contaminated soils and groundwater at the J.H. Baxter Superfund Site in Weed, California. EPA concluded that it is not possible to achieve the 1990 ROD (PB91-921489) cleanup standards for groundwater within the DNAPL zone. The remedy consists of the 1990 ROD components plus enhancements, modifications, and additional containment measures as described in this amendment. Actions have also been selected to modify other aspects of the soils remedy previously selected for the site in the 1990 ROD.

NONE

1998-09-01

418

Hesperetin 7-rutinoside (hesperidin) and taxifolin 3-arabinoside as germination and growth inhibitors in soils associated with the weed,Pluchea lanceolata (DC) C.B. Clarke (Asteraceae).  

PubMed

Hesperetin 7-rutinoside (Hesperidin) and taxifolin 3-arabinoside were detected in the soils associated with the rapidly spreading perennial weed,Pluchea lanceolata. In the present investigations, inhibitory potential of the aqueous extracts of the two compounds was established and confirmed through growth experiments pertaining to seed germination and seedling growth of radish, mustard, and tomato, with 10(-4) M solutions of the authentic samples. The significance of the water-soluble compounds present in the rhizosphere zones of the weed and its interference potential is commented upon. PMID:24257882

Inderjit; Dakshini, K M

1991-08-01

419

Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions  

NASA Astrophysics Data System (ADS)

Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30 %. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

Lanta, Vojt?ch; Doležal, Ji?í; Zemková, Lenka; Lepš, Jan

2012-06-01

420

Flavonoids from leaves of Derris urucu: assessment of potential effects on seed germination and development of weeds.  

PubMed

In some previous studies, we described the isolation of nine compounds from leaves of Derris urucu, a species found widely in the Amazon rainforest, identified as five stilbenes and four dihydroflavonols. In this work, three of these dihydroflavonols [urucuol A (1), urucuol B (2) and isotirumalin (3)] were evaluated to identify their potential as allelochemicals, and we are also reporting the isolation and structural determination of a new flavonoid [5,3'-dihydroxy-4'-methoxy-(7,6:5?,6?)-2?,2?-dimethylpyranoflavanone (4)]. We investigated the effects of the dihydroflavonols 1-3 on seed germination and radicle and hypocotyl growth of the weed Mimosa pudica, using solutions at 150 mg.L-1. Urucuol B, alone, was the substance with the greatest potential to inhibit seed germination (26%), while isotirumalin showed greater ability to reduce the development of the hypocotyl (25%), but none of the three substances showed the potential to inhibit radicle. When combined in pairs, the substances showed synergism for the development of root and hypocotyl and effects on seed germination that could be attributed to antagonism. When tested separately, the trend has become more intense effects on seed germination, while for the substances tested in pairs, the intensity of the effect was greater on development of weed. PMID:24068080

Silva, Ewerton A S da; Lôbo, Lívia T; Silva, Geilson A da; Souza Filho, Antonio Pedro Da S; Da Silva, Milton N; Arruda, Alberto C; Guilhon, Giselle M S P; Santos, Lourivaldo S; Arruda, Mara S P

2013-09-01

421

Poke weed mitogen requires Toll-like receptor ligands for proliferative activity in human and murine B lymphocytes.  

PubMed

Poke weed mitogen (PWM), a lectin purified from Phytolacca americana is frequently used as a B cell-specific stimulus to trigger proliferation and immunoglobulin secretion. In the present study we investigated the mechanisms underlying the B cell stimulatory capacity of PWM. Strikingly, we observed that highly purified PWM preparations failed to induce B cell proliferation. By contrast, commercially available PWM preparations with B cell activity contained Toll-like receptor (TLR) ligands such as TLR2-active lipoproteins, lipopolysaccharide and DNA of bacterial origin. We show that these microbial substances contribute to the stimulatory activity of PWM. Additional experimental data highlight the capacity of PWM to enable B cell activation by immunostimulatory DNA. Based on these findings we propose that the lectin sensitizes B cells for TLR stimulation as described for B cell receptor ligation and that B cell mitogenicity of PWM preparations results from synergistic activity of the poke weed lectin and microbial TLR ligands present in the PWM preparations. PMID:22238657

Bekeredjian-Ding, Isabelle; Foermer, Sandra; Kirschning, Carsten J; Parcina, Marijo; Heeg, Klaus

2012-01-01

422

The genomes of four novel begomoviruses and a new Sida micrantha mosaic virus strain from Bolivian weeds.  

PubMed

Begomovirus is the largest genus within the family Geminiviridae and includes economically important plant DNA viruses infecting a broad range of plant species and causing devastating crop diseases, mainly in subtropical and tropical countries. Besides cultivated plants, many weeds act as virus reservoirs. Eight begomovirus isolates from Bolivian weeds were examined using rolling-circle amplification (RCA) and restriction fragment length polymorphism (RFLP). An efficient, novel cloning strategy using limited Sau3A digestion to obtain tandem-repeat inserts allowed the sequencing of the complete genomes. The viruses were classified by phylogenetic analysis as typical bipartite New World begomoviruses. Four of them represented distinct new virus species, for which the names Solanum mosaic Bolivia virus, Sida mosaic Bolivia virus 1, Sida mosaic Bolivia virus 2, and Abutilon mosaic Bolivia virus are proposed. Three were variants of a new strain of Sida micrantha mosaic virus (SimMV), SimMV-rho[BoVi07], SimMV-rho[Bo:CF1:07] and SimMV-rho[Bo:CF2:07], and one was a new variant of a previously described SimMV, SimMV-MGS2:07-Bo. PMID:21170729

Wyant, Patrícia Soares; Gotthardt, Diether; Schäfer, Benjamin; Krenz, Björn; Jeske, Holger

2011-02-01

423

Symptomatology of subterranean clover red leaf virus and its incidence in some crops, weed hosts, and certain alate in Canterbury, New Zealand  

Microsoft Academic Search

Top-yellowing of peas, stunting and yellowing of dwarf beans. and leaf roll of broad beans in Canterbury, New Zealand, were found to be due almost entirely to infection with subterranean clover red leaf virus (SCRL V). SCRLV was also isolated from lupins, soya beans, and lentils and from a wide range of clovers and weed hosts including some non-leguminous species.

J. W. Ashby; P. B. Teh; R. C. Close

1979-01-01

424

Mycorrhizae, biocides, and biocontrol. 2. Mycorrhizal fungi enhance weed control and crop growth in a soybean-cocklebur association treated with the herbicide bentazon  

Microsoft Academic Search

The mediation of herbicide effects on weed-crop combinations by vesicular-arbuscular mycorrhizal (VAM) fungi is essentially unknown. We conducted a greenhouse study to determine if VAM fungi, whose hyphae interconnect the roots of adjacent plants, modify herbicide effects by enhancing nutrient fluxes between associated plants. Soybean (Glycine max (L.) Merr.) and common cocklebur (Xanthium strumarium L.) plants were grown together in

G. J. Bethlenfalvay; R. P. Schreiner; K. L. Mihara; H. McDaniel

1996-01-01

425

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

PubMed Central

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.

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

426

GRASS SEED CROPPING SYSTEMS FOR A SUSTAINABLE AGRICULTURE (GSCSSA) PROGRESS REPORT - 2006 Title: Integrated Disease, Fertilizer, Weed, and Insect Management for Columbia Basin Grass Seed Production  

Microsoft Academic Search

Objectives: 1. Conduct herbicide evaluation research to improve weed control strategies for winter annual grasses (downy brome, rattail fescue, annual bluegrass) and summer annual grasses (crabgrass, barnyard grass, witch grass) in seedling KBG under eastern Oregon irrigated conditions. Facilitate registration of herbicides for grass seed crops in the Columbia Basin. 2. Conduct trials to develop better disease control strategies, including

Philip Hamm; Daniel Ball; Donald Horneck; Silvia I. Rondon

427

Biology, host specificity, release and establishment of Macaria pallidata and Leuciris fimbriaria (Lepidoptera: Geometridae), biological control agents of the weed Mimosa pigra  

Microsoft Academic Search

Macaria pallidata (Warren) and Leuciris fimbriaria (Stoll) (Lepidoptera: Geometridae) are abundant and damaging defoliators of Mimosa pigra L. in the native range of the Neotropics. Both species were assessed for their suitability as biocontrol agents of M. pigra, a damaging invasive weed of northern Australia. Larvae feed on leaves of all ages. Adults are non-feeding, short-lived moths. Generation times are

Tim A. Heard; Louis P. Elliott; Bron Anderson; Laura White; Natasha Burrows; Arelí Mira; Ryan Zonneveld; Gio Fichera; Richard Chan; Ricardo Segura

2010-01-01

428

O.32 - Implications of the second-best decisions in weed control under social constraints: a case of wheat farming in Japan  

Microsoft Academic Search

Optimum crop protection strategies are not always feasible because of social constraints. For example, paddy-upland rotation, which is a common weed control and soil fertility management method in Japan, is not always practiced. When group decisions on cooperative land rotation that were undertaken to comply with government policy on reducing rice production have failed, rotation of upland wheat, upland soybean,

K Hayashi

2008-01-01

429

Effects of alley cropped Calliandra calothyrsus and Cliricidia sipium hedges on weed growth, soil properties, and taro yields in Western Samoa  

Microsoft Academic Search

Field experiments were conducted on a tropical Inceptisol at Apia, Western Samoa to evaluate the effects of alley cropping on soil characteristics, weed populations, and taro yield. Taro yields were compared from Calliandra calothyrsus and Gliricidia sipium alleys, spaced at 4 m, 5 m, and 6 m, and a no tree control. Measurements were made for soil moisture and temperature,

R. C. Rosecrance; S. Rogers; M. Tofinga

1992-01-01

430

Planting and Termination Dates Affect Winter Cover Crop Biomass in a Conservation-Tillage Corn-Cotton Rotation: Implications for Weed Control and Yield  

Microsoft Academic Search

Use of the winter cover crops is an integral component of the conservation system s in corn (Zea mays L.) and cotton (Gossypium hirsutum L.). A field experiment was initiated in 2004 to evaluate weed suppression provided by winter cover crops in a conservation tillage corn and cotton rotation. Rotation for winter cover crops included clover (Trifolium incarnatum L.) preceding

Monika Saini; Andrew J. Price; Edzard van Santen; Francisco J. Arriaga; Kipling S. Balkcom; Randy L. Raper

431

Laboratory host range testing of Neomusotima conspurcatalis (Lepidoptera: Crambidae) – a potential biological control agent of the invasive weed, Old World climbing fern, Lygodium microphyllum (Lygodiaceae)  

Microsoft Academic Search

Old World climbing fern, Lygodium microphyllum, is a serious invasive weed in south Florida. Development of biological control is vital for sustainable management of L. microphyllum. Neomusotima conspurcatalis was discovered in Hong Kong in 1997 and was subsequently found causing feeding damage on L. microphyllum in much of its native range in Asia. Quarantine testing of N. conspurcatalis used 37

Anthony J. Boughton; Christine A. Bennett; John A. Goolsby; Robert W. Pemberton

2009-01-01

432

Formation of Plant Canopy Hierarchies and Consequences for Water Use: Insights From Field Experiments and Individual Based Modeling of Weed-Crop Interactions  

NASA Astrophysics Data System (ADS)

In an agricultural landscape, water use is tightly linked to the dynamics of canopy development. When weeds are present, the plant community may develop leaf area faster than crop monocultures and several hierarchies of plants may be formed. The position of each individual plant within these hierarchies depends on the spatial arrangement of the plants, the initial sizes, and the availability of resources as determined by management, soil properties, weather, and competition. Together, these factors establish a highly dynamic system with nonlinear responses to the availability of resources (e.g. soil water) that is reflected in high levels of site and regional variability in crop yield losses due to weed interference. We developed a spatially-explicit, individual based model of plant competition to evaluate dynamic outcomes of crop-weed interactions and implications for water use. The model simulates the growth of individual plants using the light interception algorithms of the forest model MAESTRA, and estimates photosynthesis through the Farquhar-vonCaemmerer method. Transpiration and photosynthesis are coupled through stomatal conductance. Maximum stomatal conductance is determined by the photosynthetic demand for CO2, but under water stress, actual transpiration per plant is used to estimate stomatal conductance and then the actual rate of photosynthesis. We also used a novel approach to estimate profile water uptake, scaling the root zone of influence (volume of soil exploited by each individual plant) to plant biomass. Additive field experiments with maize in monoculture and in combination with high-density stands of a common annual weed species (A. theophrasti M.) were established to test model performance. Despite exceptionally dry conditions in the field in some years, we found no evidence that the maize-weed mixtures had less total soil water or different rates of water extraction through the profile than the maize monocrop. Furthermore, time series monitoring of stomatal conductance and end of the season harvest index indicate that corn was no more water stressed in the weedy treatments. It appears that soil water dynamics and drought severity were not significantly affected by weed competition. The similarity of entire canopy light interception for maize systems with and without weeds may explain the somewhat counter- intuitive nature of our findings. Model simulations conform to results from field experiments, and allowed us to estimate the partitioning of water use for each plant and the effects of resource scarcity on the dynamics of growth of individual plants and the formation of hierarchies within the canopy. The model was also used to asses the impact of climate variability on competition conducting simulations for a 40 year period of time and contrasting scenarios of soil nitrogen availability.

Berger, A. G.; McDonald, A. J.; Riha, S. J.

2008-12-01

433

Effects of pollutant accumulation by the invasive weed saltcedar (Tamarix ramosissima) on the biological control agent Diorhabda elongata (Coleoptera: Chrysomelidae).  

PubMed

Hydroponic greenhouse studies were used to investigate the effect of four anthropogenic pollutants (perchlorate (ClO4(-)), selenium (Se), manganese (Mn), and hexavalent chromium (Cr (VI))) on the biological control agent Diorhabda elongata Brullé. Contaminant concentrations were quantified for experimental Tamarix ramosissima Ledab. plants and D. elongata beetles. Growth of larvae was significantly reduced by Se contamination, but was not affected by the presence of perchlorate, Mn, or Cr (VI). All of the contaminants were transferred from plants to D. elongata beetles. Only Cr (VI) was accumulated at greater levels in beetles than in their food. Because T. ramosissima grows in disturbed areas, acquires salts readily, and utilizes groundwater, this plant is likely to accumulate anthropogenic pollutants in contaminated areas. This study is one of the first to investigate the potential of an anthropogenic pollutant to influence a weed biological control system. PMID:19008025

Sorensen, Mary A; Parker, David R; Trumble, John T

2009-02-01

434

Assessing Environmental Risks for Established Invasive Weeds: Dalmatian (Linaria dalmatica) and Yellow (L. vulgaris) Toadflax in North America  

PubMed Central

Environmental risk assessments characterizing potential environmental impacts of exotic weeds are more abundant and comprehensive for potential or new invaders than for widespread and well-established species such as Dalmatian (Linaria dalmatica [L.] Mill.) and yellow (L. vulgaris Mill.) toadflax. Specific effects evaluated in our assessment of environmental risks posed by yellow and Dalmatian toadflax included competitive displacement of other plant species, reservoirs of plant disease, animal and insect use, animal toxicity, human toxicity and allergenicity, erosion, and wildfire. Effect and exposure uncertainties for potential impacts of toadflax on human and ecological receptors were rated. Using publicly available information we were able to characterize ecological and human health impacts associated with toadflax, and to identify specific data gaps contributing to a high uncertainty of risk. Evidence supporting perceived negative environmental impacts of invasive toadflax was scarce.

Sing, Sharlene E.; Peterson, Robert K. D.

2011-01-01

435

Effect of effluents of a thermal power plant complex on reproductive processs of a winter season weed  

SciTech Connect

The Kasimpur Thermal Power Plant Complex (located in the District Aligarh, Uttar Pradesh, India) runs on a low grade, sulphur rich, bituminous type of coal with a daily average consumption rte of about 3,192 metric tons during winter season. Its effluents, mainly consisting of oxides of sulphur, nitrogen and carbon as well as particulate matters, were noted to affect the reproductive behavior of Melilotus indica-a winter season weed growing wild as a component of a grassland community. The samples consisting of 10 plants were collected at monthly intervals from 5 sites located about 0.5, 2, 6, 12 and 20 km leaward from the Complex. Emergence of inflorescence was delayed at the polluted sites. However, fruit formation started simultaneously (in March) at all the five sites. The pollution induced senescence of floral buds, flowers and fruits, but did not alter markedly weight of seed and fruit.

Khan, F.A.; Iqbal, M.; Ghouse, A.K.M. (Aligarh Muslim Univ. (India))

1990-05-01

436

Interactions between Population Density of the Colorado Potato Beetle, Leptinotarsa decemlineata, and Herbicide Rate for Suppression of Solanaceous Weeds  

PubMed Central

The presence of volunteer potato Solanum tuberosum L., cutleaf nightshade, S. triflorum N., and hairy nightshade, S. physalifolium Rusby (Solanales: Solanaceae), throughout potato crop rotations can diminish the effectiveness of crop rotations designed to control disease and pest problems associated with growing potatoes. In greenhouse bioassays, larvae of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) were placed in population densities of 0, 5, 10, and 40 per potato (cv. Russet Burbank) plant and 0, 5, 10, and 15 per cutleaf nightshade and hairy nightshade plant. Plants were treated with different rates of herbicides including fluroxypyr, prometryn, and mesotrione rates, and the physiological response on the potato plants was assessed by weighing shoot biomass 14 days after treatment. Consistently, across all bioassays, rate response functions were shifted as L. decemlineata density increased, such that less herbicide was required to achieve control. For instance, the herbicide rate needed to achieve 90% reduction in potato biomass was reduced from 62 to 0 g fluroxypyr per hectare and 711 to 0 g prometryn per hectare as L. decemlineata density was increased to 40 larvae per plant. Herbivory at higher L. decemlineata population densities and herbicides above certain rates resulted in large reductions in cutleaf and hairy nightshade biomass. Differences in rate response functions among L. decemlineata population densities indicated that L. decemlineata contributed to weed suppression in combination with herbicides. These data suggest that integrated weed management systems targeting volunteer potato, cutleaf nightshade, and hairy nightshade can be more effective when herbicide applications are combined with herbivory by naturally occurring Colorado potato beetles.

Metzger, Chase; Boydston, Rick; Ferguson, Holly; Williams, Martin M.; Zack, Richard; Walsh, Doug

2008-01-01

437

Interactions between population density of the Colorado potato beetle, Leptinotarsa decemlineata, and herbicide rate for suppression of solanaceous weeds.  

PubMed

The presence of volunteer potato Solanum tuberosum L., cutleaf nightshade, S. triflorum N., and hairy nightshade, S. physalifolium Rusby (Solanales: Solanaceae), throughout potato crop rotations can diminish the effectiveness of crop rotations designed to control disease and pest problems associated with growing potatoes. In greenhouse bioassays, larvae of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) were placed in population densities of 0, 5, 10, and 40 per potato (cv. Russet Burbank) plant and 0, 5, 10, and 15 per cutleaf nightshade and hairy nightshade plant. Plants were treated with different rates of herbicides including fluroxypyr, prometryn, and mesotrione rates, and the physiological response on the potato plants was assessed by weighing shoot biomass 14 days after treatment. Consistently, across all bioassays, rate response functions were shifted as L. decemlineata density increased, such that less herbicide was required to achieve control. For instance, the herbicide rate needed to achieve 90% reduction in potato biomass was reduced from 62 to 0 g fluroxypyr per hectare and 711 to 0 g prometryn per hectare as L. decemlineata density was increased to 40 larvae per plant. Herbivory at higher L. decemlineata population densities and herbicides above certain rates resulted in large reductions in cutleaf and hairy nightshade biomass. Differences in rate response functions among L. decemlineata population densities indicated that L. decemlineata contributed to weed suppression in combination with herbicides. These data suggest that integrated weed management systems targeting volunteer potato, cutleaf nightshade, and hairy nightshade can be more effective when herbicide applications are combined with herbivory by naturally occurring Colorado potato beetles. PMID:20298117

Metzger, Chase; Boydston, Rick; Ferguson, Holly; Williams, Martin M; Zack, Richard; Walsh, Doug

2008-01-01

438

Trends in atmospheric concentrations of weed pollen in the context of recent climate warming in Pozna? (Western Poland)  

NASA Astrophysics Data System (ADS)

A significant increase in summer temperatures has been observed for the period 1996-2011 in Pozna?, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Pozna? by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann-Kendall test and Sen's slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman's rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July-September daily minimum temperatures (r = -0.644, p < 0.01). In contrast, no significant correlations were found between temperature and characteristics of Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Pozna?, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.

Bogawski, Pawe?; Grewling, ?ukasz; Nowak, Ma?gorzata; Smith, Matt; Jackowiak, Bogdan

2014-01-01

439

Record of Decision Noxious Weed Management Project, Dakota Prairie Grasslands: Billings, Slope, Golden Valley, Sioux, Grant, McHenry, McKenzie, Ransom and Richland Counties in North Dakota; Corson, Perkins and Ziebach Counties in South Dakota.  

National Technical Information Service (NTIS)

This decision accompanying the Final Environmental Impact Statement (FEIS) approves the use of many different treatment methods to control noxious weeds through an integrated management strategy. Interestingly, even though weve been using herbicides, goat...

2007-01-01

440

Changes in Energy Metabolism and Antioxidant Defense Systems During Seed Germination of the Weed Species Ipomoea triloba L. and the Responses to Allelochemicals  

Microsoft Academic Search

The relationships between changes in energy metabolism and the antioxidant defense system in the weed species Ipomoea triloba L. during seed germination and early seedling growth were investigated. The effects of some common allelochemicals on these\\u000a parameters also were studied. Respiratory activity and the activities of alcohol dehydrogenase, superoxide dismutase, catalase,\\u000a guaicol peroxidase, ascorbate peroxidase, glutathione reductase, and lipoxygenase were

Érica Marusa Pergo; Emy Luiza Ishii-Iwamoto

2011-01-01

441

A field study of pollen-mediated gene flow from Mediterranean GM rice to conventional rice and the red rice weed  

Microsoft Academic Search

The objective of this study was to assess the frequency of pollen-mediated gene flow from a transgenic rice line, harbouring the gusA and the bar genes encoding respectively, ß-glucuronidase and phosphinothricin acetyl transferase as markers, to the red rice weed and conventional rice in the Spanish japonica cultivar Senia. A circular field trial design was set up to investigate the

J. Messeguer; V. Marfà; M. M. Català; E. Guiderdoni; E. Melé

2004-01-01

442

Use of different plastics for soil solarization in strawberry growth and time–temperature relationships for the control of Macrophomina phaseolina and weeds  

Microsoft Academic Search

The aim of this study was to determine the effect of soil solarization on soilborne diseases, weeds and plant yields by using\\u000a polyethylene film (30-?m-thick) containing different additives [ultraviolet (UV), ultraviolet + infrared (UV + IR), ultraviolet\\u000a + infrared + anti-fog + anti-dust (UV + IR + AF + AD)], and used polyethylene film (260-?m-thick). Trials were conducted in\\u000a commercial

Ayhan Yildiz; Seher Benlio?lu; Özhan Boz; Kemal Benlio?lu

2010-01-01

443

Superfund Record of Decision (EPA Region 9): J. H. Baxter Superfund site, Weed, CA. (First remedial action), September 1990. Final report  

SciTech Connect

The J.H. Baxter site is in Weed Siskiyou County, north-central California, and consists of the 33-acre J.H. Baxter facility and the adjacent 870-acre Roseburg Forest Products facility. Since 1937, wood treatment operations at the site have involved a variety of chemicals including ammonical copper-zinc-arsenate, creosote, and PCP. The primary contaminants of concern affecting the soil, sediment, ground water, and surface water are organics including PAHs and dioxins; and metals including arsenic.

Not Available

1990-09-27

444

The effect of externally applied electrostatic fields, microwave radiation and electric currents on plants and other organisms, with special reference to weed control  

Microsoft Academic Search

A wide-ranging review is presented of the effects of various forms of externally applied electrical energy upon plants and\\u000a other organisms. Although investigations involving both small and large amounts of energy directed at the targets are considered,\\u000a a particular emphasis of this review is the feasibility of each type of electrical stimulation for weed control.\\u000a \\u000a Electrostatic fields ranging from 100

M. F. Diprose; F. A. Benson; A. J. Willis

1984-01-01

445

The Interacting Effect of Using Urea with Fluazifop-P Herbicide on Increasing Growth and Controlling Weeds in Mungbean in the New Reclaimed Land  

Microsoft Academic Search

2 Abstract: Two field experiments were performed at summer seasons of 2006-2007 to study the promoting effect of using urea with Fluazifop -P ( fusilade) on increasing growth and controlling weeds in mungbean. The herbicide was applied alone (2 L\\/fed. as a recom. dose) and in combination (1, 1.5, and 2L) with urea (1, 2, 3%) as a post emergence

A. A. Sharara

2009-01-01

446

The origin and evolution of a recent agricultural weed: population genetic diversity of weedy populations of sunflower (Helianthus annuus L.) in Spain and France  

PubMed Central

The recurrent evolution of crop-related weeds during agricultural history raises serious economic problems and challenging scientific questions. Weedy forms of sunflower, a species native from America, have been reported in European sunflower fields for a few decades. In order to understand their origin, we analysed the genetic diversity of a sample of weedy populations from France and Spain, and of conventional and ornamental varieties. A crop-specific maternally inherited marker was present in all weeds. At 16 microsatellite loci, the weedy populations shared most of their diversity with the conventional varieties. But they showed a large number of additional alleles absent from the cultivated pool. European weedy populations thus most probably originated from the unintentional pollination of maternal lines in seed production fields by wild plants growing nearby, resulting in the introduction of crop-wild hybrids into the farmers’ fields. The wide diversity and the low population structure detected were indicative of a multiplicity of introductions events rather than of field-to-field propagation. Further studies are required to understand the local evolutionary dynamics of a weedy population, and especially the respective roles of crop-to-weed gene flow and selection in the fate of an initial source of crop-wild hybrids.

Muller, Marie-Helene; Latreille, Muriel; Tollon, Christine

2011-01-01

447

Circadian response of annual weeds in a natural setting to high and low application rates of four herbicides with different modes of actions.  

PubMed

Four herbicides [glyphosate (GLYT), an amino acid synthesis inhibitor; glufosinate (GLUF), a glutamine synthetase inhibitor; fomesafen (FOME), a protoporphyrinogen oxidase inhibitor, and chlorimuron ethyl (CLIM), an acetolactate synthase inhibitor] were used to examine the influence of time of day of application on the control of a variety of annual broadleaf weeds in field studies conducted in Minnesota (five studies on GLYT and GLUF, three studies on FOME and CLIM). All herbicides were applied with an adjuvant at recommended high and low (half or quarter strength) rates every 3h between 06:00 and 24:00h local time. Visual ratings of percent weed control evaluated at