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Sample records for lissorhoptrus oryzophilus kuschel

  1. Effect of depth of flooding on the rice water weevil, Lissorhoptrus oryzophilus, and yield of rice.

    PubMed

    Tindall, Kelly V; Bernhardt, John L; Stout, Michael J; Beighley, Donn H

    2013-01-01

    The rice water weevil, Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is a semi-aquatic pest of rice and is the most destructive insect pest of rice in the United States. Adults oviposit after floods are established, and greenhouse studies have shown that plants exposed to deep floods have more eggs oviposited in leaf sheaths than plants exposed to a shallow flood. Experiments were conducted in three mid-southern states in the USA to determine if the depth of flooding would impact numbers of L. oryzophilus on rice plants under field conditions. Rice was flooded at depths of approximately 5 or 10 cm in Arkansas in 2007 and 2008 and Louisiana in 2008, and at depths between 0-20 cm in Missouri in 2008. Plants were sampled three and four weeks after floods were established in all locations, and also two weeks after flood in Missouri. On all sampling dates in four experiments over two years and at three field sites, fewer L. oryzophilus larvae were collected from rice in shallow-flooded plots than from deep-flooded plots. The number of L. oryzophilus was reduced by as much as 27% in shallow-flooded plots. However, the reduction in insect numbers did not translate to a significant increase in rice yield. We discuss how shallow floods could be used as a component of an integrated pest management program for L. oryzophilus. PMID:23906324

  2. Integrating flood depth and plant resistance with chlorantraniliprole seed treatments for management of rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae).

    PubMed

    Lanka, Srinivas K; Blouin, David C; Stout, Michael J

    2015-10-01

    Chlorantraniliprole seed treatments in rice provide effective suppression of rice water weevil populations in the United States; however, heavy reliance on prophylactic insecticide treatments as a sole strategy could destabilize management programs for this insect. The present research evaluated the compatibility of seed treatments with two other potential management tactics-plant resistance and shallow flooding-by conducting two split-plot experiments in 2009 and 2011. In both experiments, no substantial antagonism was found among the 3 different tactics. Statistical interactions in these experiments arose from the strong and persistent effects of chlorantraniliprole on larval densities rather than incompatibility of tactics. In 2009, weevil densities differed among varieties and were significantly lower on the cultivar "Jefferson." In 2011, weevil densities were reduced significantly in shallow-flooded plots compared to deep-flooded plots. Significant reductions in weevil numbers by chlorantraniliprole seed treatments, even at application rates 5 fold lower than commercially recommended rates, demonstrated the potential to reduce application rates of this highly potent larvicide. These latter results suggest that future studies on the relationship between chlorantraniliprole seed treatment rate and weevil fitness are warranted. PMID:25176158

  3. Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice.

    PubMed

    Adams, A; Gore, J; Musser, F; Cook, D; Catchot, A; Walker, T; Awuni, G A

    2015-06-01

    Two experiments were conducted at the Delta Research and Extension Center in Stoneville, MS, during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel. Larval densities and yield were compared for plots treated with labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin and an untreated control. In the first experiment, plots were subjected to flood initiated at 6 and 8 wk after planting. Seed treatments significantly reduced larval densities with the 8-wk flood timing, but not the 6-wk flood timing. Overall, the treated plots yielded higher than the control plots. In the second experiment, the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated. Plots were subjected to zero, one, or two flushes with water. All seed treatments reduced larval densities compared with the untreated control. Significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush. All seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments. When two flushes were applied, yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots, while the chlorantraniliprole treated plots yielded significantly higher than the control. These data suggest that time from planting to flood did not impact the efficacy of seed treatments, but multiple flushes reduced the efficacy of thiamethoxam and clothianidin. PMID:26470232

  4. Efficacy of Selected Insecticides Applied to Hybrid Rice Seed.

    PubMed

    Adams, A; Gore, J; Musser, F; Cook, D; Catchot, A; Walker, T; Dobbins, C

    2016-02-01

    Hybrid rice and insecticide seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel, have altered the landscape of rice production. The effect of reduced seeding rates on seed treatment efficacy in hybrid rice has not been studied. During 2011 and 2012, an experiment was conducted at seven locations to determine the relationship between low seeding rates used in hybrid rice and efficacy of selected insecticidal seed treatments as measured by rice water weevil densities and yield. Labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin were compared with higher rates of these products to determine if labeled rates provide an acceptable level of control of the rice water weevil. Study locations were divided into low, moderate, and high groups based on rice water weevil larval densities. All seed treatments and seed treatment rates reduced rice water weevil densities. However, there was no observed yield or economic benefit from the use of an insecticidal seed treatment in areas of low pressure. Differences in yield were observed among seed treatments and seed treatment rates in moderate and high pressure locations, and all seed treatments yielded better than the untreated plots, but these differences were not always economical. All seed treatments showed an economic advantage in areas of high weevil pressure, and there were no differences among seed treatment products or rates, suggesting that currently labeled seed treatment rates in hybrid rice are effective for rice water weevil management. PMID:26537671

  5. Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice

    PubMed Central

    Adams, A.; Gore, J.; Musser, F.; Cook, D.; Catchot, A.; Walker, T.; Awuni, G. A.

    2015-01-01

    Two experiments were conducted at the Delta Research and Extension Center in Stoneville, MS, during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel. Larval densities and yield were compared for plots treated with labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin and an untreated control. In the first experiment, plots were subjected to flood initiated at 6 and 8 wk after planting. Seed treatments significantly reduced larval densities with the 8-wk flood timing, but not the 6-wk flood timing. Overall, the treated plots yielded higher than the control plots. In the second experiment, the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated. Plots were subjected to zero, one, or two flushes with water. All seed treatments reduced larval densities compared with the untreated control. Significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush. All seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments. When two flushes were applied, yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots, while the chlorantraniliprole treated plots yielded significantly higher than the control. These data suggest that time from planting to flood did not impact the efficacy of seed treatments, but multiple flushes reduced the efficacy of thiamethoxam and clothianidin. PMID:26470232

  6. Efficacy of Selected Insecticides Applied to Hybrid Rice Seed

    PubMed Central

    Adams, A.; Gore, J.; Musser, F.; Cook, D.; Walker, T.; Dobbins, C.

    2016-01-01

    Hybrid rice and insecticide seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel, have altered the landscape of rice production. The effect of reduced seeding rates on seed treatment efficacy in hybrid rice has not been studied. During 2011 and 2012, an experiment was conducted at seven locations to determine the relationship between low seeding rates used in hybrid rice and efficacy of selected insecticidal seed treatments as measured by rice water weevil densities and yield. Labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin were compared with higher rates of these products to determine if labeled rates provide an acceptable level of control of the rice water weevil. Study locations were divided into low, moderate, and high groups based on rice water weevil larval densities. All seed treatments and seed treatment rates reduced rice water weevil densities. However, there was no observed yield or economic benefit from the use of an insecticidal seed treatment in areas of low pressure. Differences in yield were observed among seed treatments and seed treatment rates in moderate and high pressure locations, and all seed treatments yielded better than the untreated plots, but these differences were not always economical. All seed treatments showed an economic advantage in areas of high weevil pressure, and there were no differences among seed treatment products or rates, suggesting that currently labeled seed treatment rates in hybrid rice are effective for rice water weevil management. PMID:26537671

  7. The impact of planting date on management of the rice water weevil in Louisiana rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rice water weevil, Lissorhoptrus oryzophilus, is the most destructive insect pest of rice in the United States. Early planting of rice to avoid damaging infestations of the rice water weevil has long been suggested as a management tactic. A five-year study was conducted to characterize the influ...

  8. Efficacy of Rice Insecticide Seed Treatments at Selected Nitrogen Rates for Control of the Rice Water Weevil (Coleoptera: Curculionidae).

    PubMed

    Everett, Mallory; Lorenz, Gus; Slaton, Nathan; Hardke, Jarrod

    2015-08-01

    Seed-applied insecticides are the standard control method used in the United States to minimize rice water weevil (Lissorhoptrus oryzophilus Kuschel) injury to rice (Oryza sativa L.) roots, and often results in greater yields than rice that receives no seed-applied insecticide. Yield increases from seed-applied insecticides often occur even when insect pressure is low and should not cause yield loss. The research objective was to evaluate the effect of urea-nitrogen rate and seed-applied insecticide on number of rice water weevil larvae, nitrogen uptake, and rice grain yield. Six trials were conducted at the Pine Tree Research Station (PTRS) and the Rice Research Extension Center (RREC) to examine the response of rice plants receiving different insecticide-seed treatments and urea-nitrogen rate combinations. Insecticide-seed treatments included label rates of clothianidin, thiamethoxam, and a no-insecticide (fungicide only) control, in combination with season-total nitrogen rates of 0, 50, 100, 150, and 200 kg urea-nitrogen/ha. Rice seed that was treated with clothianidin or thiamethoxam generally had equal numbers of rice water weevil larvae, which were significantly fewer compared with rice that received no insecticide with an equivalent urea-nitrogen rate. Nitrogen uptake at panicle differentiation was not affected by insecticide-seed treatments at four of six sites and usually increased positively and linearly as urea-nitrogen rate increased. As urea-nitrogen rate increased, grain yield increased either linearly or nonlinearly. Averaged across urea-nitrogen rates, both insecticide seed treatments had similar yields that were 4 to 7% greater than the grain yields of rice that received no insecticide at four of the five harvested sites. PMID:26470317

  9. Scanning electron micrographs of Oryzophagus oryzae (Coleoptera, Curculionidae), plastron structure and swimming behavior.

    PubMed

    Martins, Camila B C; de Almeida, Lúcia M; Zarbin, Paulo H G

    2012-02-01

    The morphological structures that permit Oryzophagus oryzae aquatic activities and swimming behavior were studied and compared with various weevils and other relevant species. The use of scanning electron microscopy facilitated the recognition of three different hydrofuge scales and sensilla. Based on the microscopic observations of behavior, morphological evidence, and comparisons with other curculionid species, it was supported that the gas exchange in O. oryzae adults relies on a subelytral air store maintained by hydrofuge scales and a ribbed margin on the adult elytra. The plastron structure is identical to Lissorhoptrus oryzophilus supporting the application of similar control measures for both species. PMID:22055468

  10. New Curculionoidea (Coleoptera) records for Canada

    PubMed Central

    Douglas, Hume; Bouchard, Patrice; Anderson, Robert S.; de Tonnancour, Pierre; Vigneault, Robert; Webster, Reginald P.

    2013-01-01

    ; Scolytus schevyrewi Semenov Tjan-Shansky, 1902; Tyloderma foveolatum (Say, 1832); (all Curculionidae); Ontario – Trichapion nigrum (Herbst, 1797); Nanophyes marmoratus marmoratus (Goeze, 1777) (both Brentidae); Asperosoma echinatum (Fall, 1917); Micracis suturalis LeConte, 1868; Orchestes alni (Linnaeus, 1758); Phloeosinus pini Swaine, 1915; Scolytus schevyrewi Semenov Tjan-Shansky, 1902; Xyleborinus attenuatus (Blandford, 1894) (all Curculionidae); Quebec – Trigonorhinus alternatus (Say, 1826); Trigonorhinus tomentosus tomentosus (Say, 1826) (both Anthribidae); Trichapion nigrum (Herbst, 1797); Trichapion porcatum (Boheman, 1839); Nanophyes marmoratus marmoratus (Goeze, 1777) (all Brentidae); Lissorhoptrus oryzophilus Kuschel, 1952 (Brachyceridae); Acalles carinatus LeConte, 1876; Ampeloglypter ampelopsis (Riley, 1869); Anthonomus rufipes LeConte, 1876; Anthonomus suturalis LeConte, 1824; Ceutorhynchus hamiltoni Dietz, 1896; Curculio pardalis (Chittenden, 1908); Cyrtepistomus castaneus (Roelofs, 1873); Larinus planus (Fabricius, 1792); Mecinus janthinus (Germar, 1821); Microhyus setiger LeConte, 1876; Microplontus campestris (Gyllenhal, 1837); Orchestes alni (Linnaeus, 1758); Otiorhynchus ligustici (Linnaeus, 1758); Rhinusa neta (Germar, 1821); Trichobaris trinotata (Say, 1832); Tychius liljebladi Blatchley, 1916; Xyleborinus attenuatus (Blandford, 1894); Xyleborus affinis Eichhoff, 1868 (all Curculionidae); Sphenophorus incongruus Chittenden, 1905 (Dryophthoridae); New Brunswick – Euparius paganus Gyllenhal, 1833; Allandrus populi Pierce, 1930; Gonotropis dorsalis (Thunberg, 1796); Euxenus punctatus LeConte, 1876 (all Anthribidae); Loborhynchapion cyanitinctum (Fall, 1927) (Brentidae); Pseudanthonomus seriesetosus Dietz, 1891; Curculio sulcatulus (Casey, 1897); Lignyodes bischoffi (Blatchley, 1916); Lignyodes horridulus (Casey, 1892); Dietzella zimmermanni (Gyllenhal, 1837); Parenthis vestitus Dietz, 1896; Pelenomus squamosus LeConte, 1876; Psomus armatus Dietz

  11. Is the Invasive Species Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae) (Argentine Stem Weevil) a Threat to New Zealand Natural Grassland Ecosystems?

    PubMed Central

    Barratt, Barbara I. P.; Barton, Diane M.; Philip, Bruce A.; Ferguson, Colin M.; Goldson, Stephen L.

    2016-01-01

    Listronotus bonariensis (Argentine stem weevil) is a stem-boring weevil that has become a major pasture pest in New Zealand, and cool climate turf grass in Australia. This species is also frequently found in native tussock grassland in New Zealand. Laboratory and field trials were established to determine the risk posed to both seedlings and established plants of three native grass species compared to what happens with a common host of this species, hybrid ryegrass (L. perenne X L. multiflorum). Adult weevil feeding damage scores were higher on Poa colensoi and Festuca novae-zelandiae than Chionochloa rigida. Oviposition was lower on P. colensoi than hybrid ryegrass, and no eggs were laid on F. novae-zelandiae. In field trials using the same four species established as spaced plants L. bonariensis laid more eggs per tiller in ryegrass in a low altitude pasture site than in ryegrass in a higher altitude site. No eggs were found on the three native grass species at the tussock sites, and only low numbers were found on other grasses at the low altitude pasture site. Despite this, numbers of adult weevils were extracted from the plants in the field trials. These may have comprised survivors of the original weevils added to the plants, together with new generation weevils that had emerged during the experiment. Irrespective, higher numbers were recovered from the tussock site plants than from those from the pasture site. It was concluded that L. bonariensis is likely to have little overall impact, but a greater impact on native grass seedling survival than on established plants. PMID:27507979

  12. A fungal endophyte helps plants to tolerate root herbivory through changes in gibberellin and jasmonate signaling.

    PubMed

    Cosme, Marco; Lu, Jing; Erb, Matthias; Stout, Michael Joseph; Franken, Philipp; Wurst, Susanne

    2016-08-01

    Plant-microbe mutualisms can improve plant defense, but the impact of root endophytes on below-ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction. Glasshouse experiments with wild-type rice and coi1-18 and Eui1-OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions. The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte-elicited GA biosynthesis suppressed the herbivore-induced JA in roots and recovered plant growth. Our study shows for the first time the impact of a root endophyte on plant defense against below-ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress. PMID:27061745

  13. Induced jasmonate signaling leads to contrasting effects on root damage and herbivore performance.

    PubMed

    Lu, Jing; Robert, Christelle Aurélie Maud; Riemann, Michael; Cosme, Marco; Mène-Saffrané, Laurent; Massana, Josep; Stout, Michael Joseph; Lou, Yonggen; Gershenzon, Jonathan; Erb, Matthias

    2015-03-01

    Induced defenses play a key role in plant resistance against leaf feeders. However, very little is known about the signals that are involved in defending plants against root feeders and how they are influenced by abiotic factors. We investigated these aspects for the interaction between rice (Oryza sativa) and two root-feeding insects: the generalist cucumber beetle (Diabrotica balteata) and the more specialized rice water weevil (Lissorhoptrus oryzophilus). Rice plants responded to root attack by increasing the production of jasmonic acid (JA) and abscisic acid, whereas in contrast to in herbivore-attacked leaves, salicylic acid and ethylene levels remained unchanged. The JA response was decoupled from flooding and remained constant over different soil moisture levels. Exogenous application of methyl JA to the roots markedly decreased the performance of both root herbivores, whereas abscisic acid and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid did not have any effect. JA-deficient antisense 13-lipoxygenase (asLOX) and mutant allene oxide cyclase hebiba plants lost more root biomass under attack from both root herbivores. Surprisingly, herbivore weight gain was decreased markedly in asLOX but not hebiba mutant plants, despite the higher root biomass removal. This effect was correlated with a herbivore-induced reduction of sucrose pools in asLOX roots. Taken together, our experiments show that jasmonates are induced signals that protect rice roots from herbivores under varying abiotic conditions and that boosting jasmonate responses can strongly enhance rice resistance against root pests. Furthermore, we show that a rice 13-lipoxygenase regulates root primary metabolites and specifically improves root herbivore growth. PMID:25627217

  14. Induced Jasmonate Signaling Leads to Contrasting Effects on Root Damage and Herbivore Performance1

    PubMed Central

    Lu, Jing; Robert, Christelle Aurélie Maud; Riemann, Michael; Cosme, Marco; Mène-Saffrané, Laurent; Massana, Josep; Stout, Michael Joseph; Lou, Yonggen; Gershenzon, Jonathan; Erb, Matthias

    2015-01-01

    Induced defenses play a key role in plant resistance against leaf feeders. However, very little is known about the signals that are involved in defending plants against root feeders and how they are influenced by abiotic factors. We investigated these aspects for the interaction between rice (Oryza sativa) and two root-feeding insects: the generalist cucumber beetle (Diabrotica balteata) and the more specialized rice water weevil (Lissorhoptrus oryzophilus). Rice plants responded to root attack by increasing the production of jasmonic acid (JA) and abscisic acid, whereas in contrast to in herbivore-attacked leaves, salicylic acid and ethylene levels remained unchanged. The JA response was decoupled from flooding and remained constant over different soil moisture levels. Exogenous application of methyl JA to the roots markedly decreased the performance of both root herbivores, whereas abscisic acid and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid did not have any effect. JA-deficient antisense 13-lipoxygenase (asLOX) and mutant allene oxide cyclase hebiba plants lost more root biomass under attack from both root herbivores. Surprisingly, herbivore weight gain was decreased markedly in asLOX but not hebiba mutant plants, despite the higher root biomass removal. This effect was correlated with a herbivore-induced reduction of sucrose pools in asLOX roots. Taken together, our experiments show that jasmonates are induced signals that protect rice roots from herbivores under varying abiotic conditions and that boosting jasmonate responses can strongly enhance rice resistance against root pests. Furthermore, we show that a rice 13-lipoxygenase regulates root primary metabolites and specifically improves root herbivore growth. PMID:25627217

  15. A Mutation in S6 of Shaker Potassium Channels Decreases the K+ Affinity of an Ion Binding Site Revealing Ion–Ion Interactions in the Pore

    PubMed Central

    Ogielska, Eva M.; Aldrich, Richard W.

    1998-01-01

    Under physiological conditions, potassium channels are extraordinarily selective for potassium over other ions. However, in the absence of potassium, certain potassium channels can conduct sodium. Sodium flux is blocked by the addition of low concentrations of potassium. Potassium affinity, and therefore the ability to block sodium current, varies among potassium channel subtypes (Korn, S.J., and S.R. Ikeda. 1995. Science. 269:410–412; Starkus, J.G., L. Kuschel, M.D. Rayner, and S.H. Heinemann. 1997. J. Gen. Physiol. 110:539–550). The Shaker potassium channel conducts sodium poorly in the presence of very low (micromolar) potassium due to its high potassium affinity (Starkus, J.G., L. Kuschel, M.D. Rayner, and S.H. Heinemann. 1997. J. Gen. Physiol. 110:539–550; Ogielska, E.M., and R.W. Aldrich. 1997. Biophys. J. 72:A233 [Abstr.]). We show that changing a single residue in S6, A463C, decreases the apparent internal potassium affinity of the Shaker channel pore from the micromolar to the millimolar range, as determined from the ability of potassium to block the sodium currents. Independent evidence that A463C decreases the apparent affinity of a binding site in the pore comes from a study of barium block of potassium currents. The A463C mutation decreases the internal barium affinity of the channel, as expected if barium blocks current by binding to a potassium site in the pore. The decrease in the apparent potassium affinity in A463C channels allows further study of possible ion interactions in the pore. Our results indicate that sodium and potassium can occupy the pore simultaneously and that multiple occupancy results in interactions between ions in the channel pore. PMID:9689030

  16. Apparent Acquired Resistance by a Weevil to Its Parasitoid Is Influenced by Host Plant.

    PubMed

    Goldson, Stephen L; Tomasetto, Federico

    2016-01-01

    Field parasitism rates of the Argentine stem weevil Listronotus bonariensis (Kuschel; Coleoptera: Curculionidae) by Microctonus hyperodae Loan (Hymenoptera: Braconidae) are known to vary according to different host Lolium species that also differ in ploidy. To further investigate this, a laboratory study was conducted to examine parasitism rates on tetraploid Italian Lolium multiflorum, diploid Lolium perenne and diploid hybrid L. perenne ×L. multiflorum; none of which were infected by Epichloë endophyte. At the same time, the opportunity was taken to compare the results of this study with observations made during extensive laboratory-based research and parasitoid-rearing in the 1990s using the same host plant species. This made it possible to determine whether there has been any change in weevil susceptibility to the parasitoid over a 20 year period when in the presence of the tetraploid Italian, diploid perennial and hybrid host grasses that were commonly in use in the 1990's. The incidence of parasitism in cages, in the presence of these three grasses mirrored what has recently been observed in the field. When caged, weevil parasitism rates in the presence of a tetraploid Italian ryegrass host were significantly higher (75%) than rates that occurred in the presence of either the diploid perennial (46%) or the diploid hybrid (52%) grass, which were not significantly different from each other. This is very different to laboratory parasitism rates in the 1990s when in the presence of both of the latter grasses high rates of parasitism (c. 75%) were recorded. These high rates are typical of those still found in weevils in the presence of both field and caged tetraploid Italian grasses. In contrast, the abrupt decline in weevil parasitism rates points to the possibility of evolved resistance by the weevil to the parasitoid in the diploid and hybrid grasses, but not so in the tetraploid. The orientation of plants in the laboratory cages had no significant effect on

  17. Apparent Acquired Resistance by a Weevil to Its Parasitoid Is Influenced by Host Plant

    PubMed Central

    Goldson, Stephen L.; Tomasetto, Federico

    2016-01-01

    Field parasitism rates of the Argentine stem weevil Listronotus bonariensis (Kuschel; Coleoptera: Curculionidae) by Microctonus hyperodae Loan (Hymenoptera: Braconidae) are known to vary according to different host Lolium species that also differ in ploidy. To further investigate this, a laboratory study was conducted to examine parasitism rates on tetraploid Italian Lolium multiflorum, diploid Lolium perenne and diploid hybrid L. perenne ×L. multiflorum; none of which were infected by Epichloë endophyte. At the same time, the opportunity was taken to compare the results of this study with observations made during extensive laboratory-based research and parasitoid-rearing in the 1990s using the same host plant species. This made it possible to determine whether there has been any change in weevil susceptibility to the parasitoid over a 20 year period when in the presence of the tetraploid Italian, diploid perennial and hybrid host grasses that were commonly in use in the 1990’s. The incidence of parasitism in cages, in the presence of these three grasses mirrored what has recently been observed in the field. When caged, weevil parasitism rates in the presence of a tetraploid Italian ryegrass host were significantly higher (75%) than rates that occurred in the presence of either the diploid perennial (46%) or the diploid hybrid (52%) grass, which were not significantly different from each other. This is very different to laboratory parasitism rates in the 1990s when in the presence of both of the latter grasses high rates of parasitism (c. 75%) were recorded. These high rates are typical of those still found in weevils in the presence of both field and caged tetraploid Italian grasses. In contrast, the abrupt decline in weevil parasitism rates points to the possibility of evolved resistance by the weevil to the parasitoid in the diploid and hybrid grasses, but not so in the tetraploid. The orientation of plants in the laboratory cages had no significant effect

  18. A taxonomic monograph of the genus Tylodinus Champion (Coleoptera: Curculionidae: Cryptorhynchinae: Tylodina) of Chiapas, Mexico.

    PubMed

    Luna-Cozar, Jesús; Anderson, Robert S; Jones, Robert W; León-Corté, Jorge L

    2014-01-01

    nodulosus species group (3) T. andersoni new species (Chiapas, Ángel Albino Corzo, Reserva El Triunfo, Polígono 1), T. nodulosus (Boheman), T. zilchi Kuschel; Tylodinus pusillus species group (2) T. porvenirensis new species (type locality: Chiapas, El Porvenir, El Porvenir (2 km NE)), T. pusillus new species (type locality: Chiapas, 4 km SE Custepec); Tylodinus spiniventris species group (2) T. lum new species (Chiapas, San Cristóbal de las Casas, Cerro Huitepec), and T. spiniventris new species (type locality: Chiapas, San Cristóbal de las Casas, Reserva Huitepec); Incertae sedis (13) T. pinguis new species (type locality: Chiapas, Ángel Albino Corzo, Reserva El Triunfo, Polígono 1) , T. kissingeri new species (type locality: Chiapas, Tapalapa, ca. 14 km NE Coapilla), T. complicatus new species (type locality: Chiapas, Pueblo Nuevo Solistahuacán, La Yerbabuena), T. dominicus new species (type locality: Chiapas, Villa Corzo, Reserva de la Biósfera La Sepultura), T. noctis new species (type locality: Chiapas, Coapilla, ca. 10.5 km NE Coapilla), T. rufus new species (type locality: Chiapas, San Cristóbal de las Casas, Cerro Huitepec); T. branstetteri new species (type locality: Chiapas, La Concordia, 4 km SE Custepec), T. kuscheli new species (type locality: Chiapas, Villa Flores, Ejido Sierra Morena), T. pappi new species (type locality: Chiapas, Unión Juárez, Volcán Tacan), T. gibbosus new species (type locality: Chiapas, Pueblo Nuevo Solistahuacán, Yerbabuena Reserve), T. immundus new species (type locality: Chiapas, San Cristóbal de las Casas Cerro Huitepec), T. intzin new species (type locality: Chiapas, Tenejapa, Yashanal), T. elongatus new species (type locality: Chiapas, Ángel Albino Corzo, Reserva El Triunfo, Polígono 1). Three species (T. nodulosus (Boheman), T. zilchi Kuschel and T. cavicrus Champion) are not known to occur in Chiapas but were included in this study to be more representative of inter- and intraspecific variation and to provide a