Aim The objective of this research was to screen fungal isolates originally isolated from cotton ... more Aim The objective of this research was to screen fungal isolates originally isolated from cotton plants and measure their effects on the interactions between soybean and two aboveground pests (cabbage looper; Trichoplusia ni and soybean looper; Chrysodeixis includens) as well as a belowground pest (soybean cyst nematode; Heterodera glycines). Methods and Results For aboveground pests, we measured the leaf area consumed and larval weight. For our belowground pest tests, we measured shoot height, shoot fresh weight, root fresh weight and number of cysts. Out of the 50 fungal isolates tested, we tested 30 fungi in the interaction with cabbage looper, 36 for soybean looper, 41 for soybean cyst nematode. We tested 23 isolates against all pests and identified multiple isolates that significantly changed the response of pests on inoculated soybean plants versus controls. Conclusions We identified three fungal isolates that significantly reduced both leaf area consumed aboveground by caterp...
Background: At the time of publication, the most devastating desert locust crisis in decades is a... more Background: At the time of publication, the most devastating desert locust crisis in decades is affecting East Africa, the Arabian Peninsula and South-West Asia. The situation is extremely alarming in East Africa, where Kenya, Ethiopia and Somalia face an unprecedented threat to food security and livelihoods. Most of the time, however, locusts do not occur in swarms, but live as relatively harmless solitary insects. The phenotypically distinct solitarious and gregarious locust phases differ markedly in many aspects of behaviour, physiology and morphology, making them an excellent model to study how environmental factors shape behaviour and development. A better understanding of the extreme phenotypic plasticity in desert locusts will offer new, more environmentally sustainable ways of fighting devastating swarms. Methods: High molecular weight DNA derived from two adult males was used for Mate Pair and Paired End Illumina sequencing and PacBio sequencing. A reliable reference genome...
Many animals, including insects, demonstrate a remarkable ability to regulate their intake of key... more Many animals, including insects, demonstrate a remarkable ability to regulate their intake of key macronutrients (e.g., soluble protein and digestible carbohydrates), which allows them to optimize fitness and performance. Additionally, regulating the intake of these two macronutrients enhances an animal's ability to defend itself against pathogens, mitigate the effects of secondary plant metabolites, and decrease susceptibility to toxins. In this study, we first compared how Bt-resistant and -susceptible lines of Helicoverpa armigera and Helicoverpa punctigera regulate their intake of protein (p) and digestible carbohydrates (c). We found that there was no difference in the self-selected protein-carbohydrate intake target between resistant and susceptible genotypes of either species. We then explored the extent to which food protein-carbohydrate content altered the susceptibility of these species to three Bt toxins: Cry1Ac, Cry2Ab, and Vip3Aa. We found that H. armigera on diets ...
Plant soluble protein and digestible carbohydrate content significantly affect insect herbivore f... more Plant soluble protein and digestible carbohydrate content significantly affect insect herbivore fitness, but studies reporting plant protein and carbohydrate content are rare. Instead, the elements nitrogen and carbon often are used as surrogates for plant protein and digestible carbohydrate content, respectively. However, this is problematic for two reasons. First, carbon is found in all organic molecules, which precludes strong correlations with ecologically important dietary macronutrients (e.g., digestible carbohydrates, the primary energy source for most insect herbivores). Second, some elements (e.g., nitrogen) are present in both macronutrients (e.g., protein) and non-nutritive secondary compounds (e.g., alkaloids, protease inhibitors); in these cases N values would greatly overestimate protein available for an insect herbivore. Thus, the objective of this study was to explicitly document plant protein-carbohydrate content and assess its variation in cotton (Gossypium hirsutu...
Incidents of insecticide resistance in agricultural pest species represent a costly and ever-incr... more Incidents of insecticide resistance in agricultural pest species represent a costly and ever-increasing problem that poses significant challenges for meeting the nutritional demands of our growing global population. The development and spread of genetic mutations conferring resistance is the primary explanation for observations of low pesticide efficacy and population outbreaks in agricultural systems. Unfortunately, in many cases it takes years to identify the mutations and alleles responsible for these resistant phenotypes, with most incidents assumed to be the result of mutations without any substantiation. As a result, the potential for gene-by-environment interactions to play a dominant role in mediating pesticide resistance is often overlooked. One environmental factor that has been shown to be highly variable is plant macronutrient content. Macronutrients such as protein (P) and carbohydrates (C) have also been shown to strongly affect insect behavior, physiology, and perform...
ABSTRACT Background/Question/Methods Understanding the nutritional preferences and constraints on... more ABSTRACT Background/Question/Methods Understanding the nutritional preferences and constraints on insect herbivores is integral to predicting when and where they will occur in ecosystems. Advances in the fields of nutritional ecology and physiology have shown that the balance of dietary macronutrients, particularly protein and carbohydrates, have significant impacts on insect performance. Despite this, information regarding plant macronutrient content is poorly documented, and data on the variability of these nutrients within individual plants and between species and environments are even more obscure. Elemental data on nitrogen (N) and carbon (C) content is common in the literature; however, it is difficult to accurately extrapolate protein and carbohydrate content from these data given that a large portion of plant N and C pools include non-nutritional compounds, such as cellulose/lignin, or toxic compounds, such as C- and N-containing allelochemicals. In this study protein and digestible carbohydrate content of cotton tissues (true leaves, terminal growth, squares, and bolls) were measured, as well as N and C, across several varieties in the field and greenhouse to: (1) determine the macronutrient content of different cotton tissues, (2) compare these concentrations across different varieties and environments, (3) and to determine how total N and C measures correspond to macronutrient concentrations. Results/Conclusions Results show that there was a significant amount of variation in macronutrient content across tissues and environments; however, there were no differences in either nutrient across varieties. In both environments bolls had the highest carbohydrate content and the lowest protein content, a surprising result considering that many insect herbivores are thought to be more protein-limited and feed preferentially on fruiting bodies. In general, the foliar tissues had relatively high amounts of both carbohydrates and protein. Under greenhouse conditions terminal growth, true leaves, and squares had similar carbohydrate values, while true leaves and squares showed a significant reduction in carbohydrate content in the field. There was also a significant decrease in true leaf protein content in the field. Overall, there was greater variability in protein content across tissues in the greenhouse and greater variability in carbohydrate content across tissues in the field. These results show that cotton macronutrient content is highly variable across different tissues, providing a broad nutritional gradient for insect herbivores even within a single plant. These results also show that plant nutrient content is likely to be a large contributor to the environmental variability in these systems, which have important implications for insect performance and pest population dynamics.
Pesticide resistance represents a major challenge to global food production. The spread of resist... more Pesticide resistance represents a major challenge to global food production. The spread of resistance alleles is the primary explanation for observations of reduced pesticide efficacy over time, but the potential for gene-by-environment interactions (plasticity) to mediate susceptibility has largely been overlooked. Here we show that nutrition is an environmental factor that affects susceptibility to Bt toxins. Protein and carbohydrates are two key macronutrients for insect herbivores, and the polyphagous pest Helicoverpa zea self-selects and performs best on diets that are protein-biased relative to carbohydrates. Despite this, most Bt bioassays employ carbohydrate-biased rearing diets. This study explored the effect of diet protein-carbohydrate content on H. zea susceptibility to Cry1Ac, a common Bt endotoxin. We detected a 100-fold increase in LC50 for larvae on optimal versus carbohydrate-biased diets, and significant diet-mediated variation in survival and performance when chal...
The boll weevil (Anthonomus grandis Boheman) reproduces on a reported 13 species of wild host pla... more The boll weevil (Anthonomus grandis Boheman) reproduces on a reported 13 species of wild host plants in North America, two in the United States and 12 in Mexico. The distributions of these plants are of economic importance to pest management and provide insight into the evolutionary history and origin of the BW. However, detailed information regarding the distributions of many of these species is lacking. In this article, we present distribution models for all of the reported significant BW host plants from Mexico and the United States using spatial distribution modelling software. Host plant distributions were divided into two groups: “eastern” and “western.” In Mexico, Hampea nutricia along the Gulf Coast was the most important of the eastern group, and the wild cottons, Gossypium aridum and Gossypium thurberi were most important in the western group. Other species of Hampea, Gossypium, and Cienfuegosia rosei have relatively restricted distributions and are of apparent minimal eco...
Microbes have the potential to affect multitrophic plant–insect–predator interactions. We examine... more Microbes have the potential to affect multitrophic plant–insect–predator interactions. We examined whether cotton plants treated with potentially beneficial fungi affect interactions between cotton aphids Aphis gossypii and predatory lady beetles Hippodamia convergens. We used Y-tube olfactometer assays to test lady beetle behavioral responses to stimuli emitted by aphid-infested and non-infested cotton plants grown from seeds treated with either Phialemonium inflatum (TAMU490) or Chaetomium globosum (TAMU520) versus untreated control plants. We tested a total of 960 lady beetles (480 males and 480 females) that had been deprived of food for approximately 24 h. In the absence of any fungal treatments, males preferred stimuli from aphid-infested plants, and females spent more time associated with stimuli from aphid-infested versus non-infested plants. When fungal treatments were added, we observed that lady beetles preferred non-aphid-infested P. inflatum plants, and males responded ...
Abstract. Since the success of the U.S. Boll Weevil Eradication Program and widespread adoption o... more Abstract. Since the success of the U.S. Boll Weevil Eradication Program and widespread adoption of genetically modified crops, the cotton fleahopper, Pseudatomoscelis seriatus (Reuter), has reemerged as a significant cotton pest. Current management strategies for the pest are based primarily on foliar applications of insecticides. A line of cotton that produces modified Bt Cry51Aa2 protein was developed for Lygus spp., but the protein has also shown activity against the cotton fleahopper. Consequently, before this new Bt line can be released commercially, refuge requirements and other Insect Resistance Management (IRM) strategies mandated by the Environmental Protection Agency need to be established to prevent or delay development of resistance by cotton fleahopper to the new toxin. In response, we provide and discuss relevant information on the biology and ecology of the cotton fleahopper, including life history, host preference, dispersal, and population genetic structure, that may be useful for developing IRM strategies for the pest.
Many methods for trajectory simulation, such as Hybrid Single-Particle Lagrangian Integrated Traj... more Many methods for trajectory simulation, such as Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), have been developed over the past several decades and contributed greatly to our knowledge in insect migratory movement. To improve the accuracy of trajectory simulation, we developed a new numerical trajectory model, in which the self-powered flight behaviors of insects are considered and trajectory calculation is driven by high spatio-temporal resolution weather conditions simulated by the Weather Research and Forecasting (WRF) model. However, a rigorous evaluation of the accuracy of different trajectory models on simulated long-distance migration is lacking. Hence, in this study our trajectory model was evaluated by a migration event of the corn earworm moth, Helicoverpa zea, in Texas, USA on 20–22 March 1995. The results indicate that the simulated migration trajectories are in good agreement with occurrences of all pollen-marked male H. zea immigrants monitored in ...
Plant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insec... more Plant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insect pest groups impacting cotton production in the USA today, but are not controlled by current transgenic cotton varieties. Thus, seed or foliar-applied chemical insecticides are typically required to protect cotton from these pest groups. Currently, these pests are resistant to several insecticides, resulting in fewer options for economically viable management. Previous publications documented the efficacy of transgenic cotton event MON 88702 against plant bugs and thrips in limited laboratory and field studies. Here, we report results from multi-location and multi-year field studies demonstrating efficacy provided by MON 88702 against various levels of these pests. MON 88702 provided a significant reduction in numbers of Lygus nymphs and subsequent yield advantage. MON 88702 also had fewer thrips and minimal injury. The level of control demonstrated by this transgenic trait was signific...
Progress has been made in understanding the mechanisms underlying directional navigation in migra... more Progress has been made in understanding the mechanisms underlying directional navigation in migratory insects, yet the magnetic compass involved has not been fully elucidated. Here we developed a flight simulation system to study the flight directionality of the migratory armyworm Mythimna separata in response to magnetic fields. Armyworm moths were exposed to either a 500nT extreme weak magnetic field, 1.8T strong magnetic field, or a deflecting magnetic field and subjected to tethered flight trials indoors in the dark. The moths were disoriented in the extreme weak magnetic field, with flight vectors that were more dispersed (variance=0.60) than in the geomagnetic field (variance=0.32). After exposure to a 1.8T strong magnetic field, the mean flight vectors were shifted by about 105°in comparison with those in the geomagnetic field. In the deflecting magnetic field, the flight directions varied with the direction of the magnetic field, and also pointed to the same direction of the...
Phase polyphenism is a form of phenotypic plasticity in which the expression of a variety of trai... more Phase polyphenism is a form of phenotypic plasticity in which the expression of a variety of traits can be affected by local population density. We tested for the expression of density-dependent phase polyphenism in the fall armyworm, Spodoptera frugiperta. Larval coloration, development time, pupal weight and pathogen resistance were compared between individuals reared under isolated versus crowded conditions. When reared at high densities, the larvae exhibited a smaller body size and darker cuticular melanization than larvae reared singly. The phenotypic switch to a rapidly developing dark phase at high densities could be interpreted as an adaptive responses to reach pupation before food supplies are depleted, thereby minimizing the effects of intraspecific competition when larval density is high. However, larvae reared singly appeared to be more cannibalistic than crowd-reared larvae. This is inconsistent with the prediction that cannibalism increases at high densities in respons...
Aim The objective of this research was to screen fungal isolates originally isolated from cotton ... more Aim The objective of this research was to screen fungal isolates originally isolated from cotton plants and measure their effects on the interactions between soybean and two aboveground pests (cabbage looper; Trichoplusia ni and soybean looper; Chrysodeixis includens) as well as a belowground pest (soybean cyst nematode; Heterodera glycines). Methods and Results For aboveground pests, we measured the leaf area consumed and larval weight. For our belowground pest tests, we measured shoot height, shoot fresh weight, root fresh weight and number of cysts. Out of the 50 fungal isolates tested, we tested 30 fungi in the interaction with cabbage looper, 36 for soybean looper, 41 for soybean cyst nematode. We tested 23 isolates against all pests and identified multiple isolates that significantly changed the response of pests on inoculated soybean plants versus controls. Conclusions We identified three fungal isolates that significantly reduced both leaf area consumed aboveground by caterp...
Background: At the time of publication, the most devastating desert locust crisis in decades is a... more Background: At the time of publication, the most devastating desert locust crisis in decades is affecting East Africa, the Arabian Peninsula and South-West Asia. The situation is extremely alarming in East Africa, where Kenya, Ethiopia and Somalia face an unprecedented threat to food security and livelihoods. Most of the time, however, locusts do not occur in swarms, but live as relatively harmless solitary insects. The phenotypically distinct solitarious and gregarious locust phases differ markedly in many aspects of behaviour, physiology and morphology, making them an excellent model to study how environmental factors shape behaviour and development. A better understanding of the extreme phenotypic plasticity in desert locusts will offer new, more environmentally sustainable ways of fighting devastating swarms. Methods: High molecular weight DNA derived from two adult males was used for Mate Pair and Paired End Illumina sequencing and PacBio sequencing. A reliable reference genome...
Many animals, including insects, demonstrate a remarkable ability to regulate their intake of key... more Many animals, including insects, demonstrate a remarkable ability to regulate their intake of key macronutrients (e.g., soluble protein and digestible carbohydrates), which allows them to optimize fitness and performance. Additionally, regulating the intake of these two macronutrients enhances an animal's ability to defend itself against pathogens, mitigate the effects of secondary plant metabolites, and decrease susceptibility to toxins. In this study, we first compared how Bt-resistant and -susceptible lines of Helicoverpa armigera and Helicoverpa punctigera regulate their intake of protein (p) and digestible carbohydrates (c). We found that there was no difference in the self-selected protein-carbohydrate intake target between resistant and susceptible genotypes of either species. We then explored the extent to which food protein-carbohydrate content altered the susceptibility of these species to three Bt toxins: Cry1Ac, Cry2Ab, and Vip3Aa. We found that H. armigera on diets ...
Plant soluble protein and digestible carbohydrate content significantly affect insect herbivore f... more Plant soluble protein and digestible carbohydrate content significantly affect insect herbivore fitness, but studies reporting plant protein and carbohydrate content are rare. Instead, the elements nitrogen and carbon often are used as surrogates for plant protein and digestible carbohydrate content, respectively. However, this is problematic for two reasons. First, carbon is found in all organic molecules, which precludes strong correlations with ecologically important dietary macronutrients (e.g., digestible carbohydrates, the primary energy source for most insect herbivores). Second, some elements (e.g., nitrogen) are present in both macronutrients (e.g., protein) and non-nutritive secondary compounds (e.g., alkaloids, protease inhibitors); in these cases N values would greatly overestimate protein available for an insect herbivore. Thus, the objective of this study was to explicitly document plant protein-carbohydrate content and assess its variation in cotton (Gossypium hirsutu...
Incidents of insecticide resistance in agricultural pest species represent a costly and ever-incr... more Incidents of insecticide resistance in agricultural pest species represent a costly and ever-increasing problem that poses significant challenges for meeting the nutritional demands of our growing global population. The development and spread of genetic mutations conferring resistance is the primary explanation for observations of low pesticide efficacy and population outbreaks in agricultural systems. Unfortunately, in many cases it takes years to identify the mutations and alleles responsible for these resistant phenotypes, with most incidents assumed to be the result of mutations without any substantiation. As a result, the potential for gene-by-environment interactions to play a dominant role in mediating pesticide resistance is often overlooked. One environmental factor that has been shown to be highly variable is plant macronutrient content. Macronutrients such as protein (P) and carbohydrates (C) have also been shown to strongly affect insect behavior, physiology, and perform...
ABSTRACT Background/Question/Methods Understanding the nutritional preferences and constraints on... more ABSTRACT Background/Question/Methods Understanding the nutritional preferences and constraints on insect herbivores is integral to predicting when and where they will occur in ecosystems. Advances in the fields of nutritional ecology and physiology have shown that the balance of dietary macronutrients, particularly protein and carbohydrates, have significant impacts on insect performance. Despite this, information regarding plant macronutrient content is poorly documented, and data on the variability of these nutrients within individual plants and between species and environments are even more obscure. Elemental data on nitrogen (N) and carbon (C) content is common in the literature; however, it is difficult to accurately extrapolate protein and carbohydrate content from these data given that a large portion of plant N and C pools include non-nutritional compounds, such as cellulose/lignin, or toxic compounds, such as C- and N-containing allelochemicals. In this study protein and digestible carbohydrate content of cotton tissues (true leaves, terminal growth, squares, and bolls) were measured, as well as N and C, across several varieties in the field and greenhouse to: (1) determine the macronutrient content of different cotton tissues, (2) compare these concentrations across different varieties and environments, (3) and to determine how total N and C measures correspond to macronutrient concentrations. Results/Conclusions Results show that there was a significant amount of variation in macronutrient content across tissues and environments; however, there were no differences in either nutrient across varieties. In both environments bolls had the highest carbohydrate content and the lowest protein content, a surprising result considering that many insect herbivores are thought to be more protein-limited and feed preferentially on fruiting bodies. In general, the foliar tissues had relatively high amounts of both carbohydrates and protein. Under greenhouse conditions terminal growth, true leaves, and squares had similar carbohydrate values, while true leaves and squares showed a significant reduction in carbohydrate content in the field. There was also a significant decrease in true leaf protein content in the field. Overall, there was greater variability in protein content across tissues in the greenhouse and greater variability in carbohydrate content across tissues in the field. These results show that cotton macronutrient content is highly variable across different tissues, providing a broad nutritional gradient for insect herbivores even within a single plant. These results also show that plant nutrient content is likely to be a large contributor to the environmental variability in these systems, which have important implications for insect performance and pest population dynamics.
Pesticide resistance represents a major challenge to global food production. The spread of resist... more Pesticide resistance represents a major challenge to global food production. The spread of resistance alleles is the primary explanation for observations of reduced pesticide efficacy over time, but the potential for gene-by-environment interactions (plasticity) to mediate susceptibility has largely been overlooked. Here we show that nutrition is an environmental factor that affects susceptibility to Bt toxins. Protein and carbohydrates are two key macronutrients for insect herbivores, and the polyphagous pest Helicoverpa zea self-selects and performs best on diets that are protein-biased relative to carbohydrates. Despite this, most Bt bioassays employ carbohydrate-biased rearing diets. This study explored the effect of diet protein-carbohydrate content on H. zea susceptibility to Cry1Ac, a common Bt endotoxin. We detected a 100-fold increase in LC50 for larvae on optimal versus carbohydrate-biased diets, and significant diet-mediated variation in survival and performance when chal...
The boll weevil (Anthonomus grandis Boheman) reproduces on a reported 13 species of wild host pla... more The boll weevil (Anthonomus grandis Boheman) reproduces on a reported 13 species of wild host plants in North America, two in the United States and 12 in Mexico. The distributions of these plants are of economic importance to pest management and provide insight into the evolutionary history and origin of the BW. However, detailed information regarding the distributions of many of these species is lacking. In this article, we present distribution models for all of the reported significant BW host plants from Mexico and the United States using spatial distribution modelling software. Host plant distributions were divided into two groups: “eastern” and “western.” In Mexico, Hampea nutricia along the Gulf Coast was the most important of the eastern group, and the wild cottons, Gossypium aridum and Gossypium thurberi were most important in the western group. Other species of Hampea, Gossypium, and Cienfuegosia rosei have relatively restricted distributions and are of apparent minimal eco...
Microbes have the potential to affect multitrophic plant–insect–predator interactions. We examine... more Microbes have the potential to affect multitrophic plant–insect–predator interactions. We examined whether cotton plants treated with potentially beneficial fungi affect interactions between cotton aphids Aphis gossypii and predatory lady beetles Hippodamia convergens. We used Y-tube olfactometer assays to test lady beetle behavioral responses to stimuli emitted by aphid-infested and non-infested cotton plants grown from seeds treated with either Phialemonium inflatum (TAMU490) or Chaetomium globosum (TAMU520) versus untreated control plants. We tested a total of 960 lady beetles (480 males and 480 females) that had been deprived of food for approximately 24 h. In the absence of any fungal treatments, males preferred stimuli from aphid-infested plants, and females spent more time associated with stimuli from aphid-infested versus non-infested plants. When fungal treatments were added, we observed that lady beetles preferred non-aphid-infested P. inflatum plants, and males responded ...
Abstract. Since the success of the U.S. Boll Weevil Eradication Program and widespread adoption o... more Abstract. Since the success of the U.S. Boll Weevil Eradication Program and widespread adoption of genetically modified crops, the cotton fleahopper, Pseudatomoscelis seriatus (Reuter), has reemerged as a significant cotton pest. Current management strategies for the pest are based primarily on foliar applications of insecticides. A line of cotton that produces modified Bt Cry51Aa2 protein was developed for Lygus spp., but the protein has also shown activity against the cotton fleahopper. Consequently, before this new Bt line can be released commercially, refuge requirements and other Insect Resistance Management (IRM) strategies mandated by the Environmental Protection Agency need to be established to prevent or delay development of resistance by cotton fleahopper to the new toxin. In response, we provide and discuss relevant information on the biology and ecology of the cotton fleahopper, including life history, host preference, dispersal, and population genetic structure, that may be useful for developing IRM strategies for the pest.
Many methods for trajectory simulation, such as Hybrid Single-Particle Lagrangian Integrated Traj... more Many methods for trajectory simulation, such as Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), have been developed over the past several decades and contributed greatly to our knowledge in insect migratory movement. To improve the accuracy of trajectory simulation, we developed a new numerical trajectory model, in which the self-powered flight behaviors of insects are considered and trajectory calculation is driven by high spatio-temporal resolution weather conditions simulated by the Weather Research and Forecasting (WRF) model. However, a rigorous evaluation of the accuracy of different trajectory models on simulated long-distance migration is lacking. Hence, in this study our trajectory model was evaluated by a migration event of the corn earworm moth, Helicoverpa zea, in Texas, USA on 20–22 March 1995. The results indicate that the simulated migration trajectories are in good agreement with occurrences of all pollen-marked male H. zea immigrants monitored in ...
Plant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insec... more Plant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insect pest groups impacting cotton production in the USA today, but are not controlled by current transgenic cotton varieties. Thus, seed or foliar-applied chemical insecticides are typically required to protect cotton from these pest groups. Currently, these pests are resistant to several insecticides, resulting in fewer options for economically viable management. Previous publications documented the efficacy of transgenic cotton event MON 88702 against plant bugs and thrips in limited laboratory and field studies. Here, we report results from multi-location and multi-year field studies demonstrating efficacy provided by MON 88702 against various levels of these pests. MON 88702 provided a significant reduction in numbers of Lygus nymphs and subsequent yield advantage. MON 88702 also had fewer thrips and minimal injury. The level of control demonstrated by this transgenic trait was signific...
Progress has been made in understanding the mechanisms underlying directional navigation in migra... more Progress has been made in understanding the mechanisms underlying directional navigation in migratory insects, yet the magnetic compass involved has not been fully elucidated. Here we developed a flight simulation system to study the flight directionality of the migratory armyworm Mythimna separata in response to magnetic fields. Armyworm moths were exposed to either a 500nT extreme weak magnetic field, 1.8T strong magnetic field, or a deflecting magnetic field and subjected to tethered flight trials indoors in the dark. The moths were disoriented in the extreme weak magnetic field, with flight vectors that were more dispersed (variance=0.60) than in the geomagnetic field (variance=0.32). After exposure to a 1.8T strong magnetic field, the mean flight vectors were shifted by about 105°in comparison with those in the geomagnetic field. In the deflecting magnetic field, the flight directions varied with the direction of the magnetic field, and also pointed to the same direction of the...
Phase polyphenism is a form of phenotypic plasticity in which the expression of a variety of trai... more Phase polyphenism is a form of phenotypic plasticity in which the expression of a variety of traits can be affected by local population density. We tested for the expression of density-dependent phase polyphenism in the fall armyworm, Spodoptera frugiperta. Larval coloration, development time, pupal weight and pathogen resistance were compared between individuals reared under isolated versus crowded conditions. When reared at high densities, the larvae exhibited a smaller body size and darker cuticular melanization than larvae reared singly. The phenotypic switch to a rapidly developing dark phase at high densities could be interpreted as an adaptive responses to reach pupation before food supplies are depleted, thereby minimizing the effects of intraspecific competition when larval density is high. However, larvae reared singly appeared to be more cannibalistic than crowd-reared larvae. This is inconsistent with the prediction that cannibalism increases at high densities in respons...
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