Location: Pest Management and Biocontrol Research
Project Number: 2020-22620-022-000-D
Project Type: In-House Appropriated
Start Date: Jul 1, 2015
End Date: Jun 30, 2020
1: Improve biological control of key pests by quantifying interactions between prey & generalist predators, including predators occupying different trophic levels, using molecular marking & gut content assays in the field & defining impacts of transgenic crops on non-target species through meta-analyses. Sub-objective 1A through 1B: See uploaded project plan. Sub-objective 1C: Examine temporal and spatial dynamics of whitefly, Lygus, predator and pollinator movements between cotton and Vernonia, a new industrial crop.(New, May, 2018) Sub-objective 1D: Assess the risk of disruption of biological control of whiteflies by the introduction of a new Bt cotton with activity against Lygus bugs and thrips.(New, May, 2018) 2: Refine resistance management strategies based on improved knowledge of host (species & phenology) & environmental (temperature) influences on inducible mechanisms of stress response in whitefly & lygus & of Cry-toxin binding & mechanisms of Bt (Bacillus thuringiensis) toxin resistance in pink bollworm. Sub-objective 2A through 2C: See uploaded project plan. 3: Refine knowledge of factors regulating mate-finding & the dynamics of reproduction in lygus & whitefly by optimizing lygus sex pheromone doses & component ratios, defining insect phenology-dependent roles of short-range cues of lygus mating receptivity, & quantifying impacts of host, environmental, & population density-based factors on whitefly sex ratios. Sub-objective 3A through 3D: See uploaded project plan. 4: Define key life history parameters including the development & survival strategies of lygus & key species of beneficial insects in relation to the environment by quantifying consequences of extreme thermal environments & defining insect stage- dependent & environment-dependent diapause responses & associated transcriptional- based & endocrine-based patterns in lygus. Sub-objective 4A through 4C: See uploaded project plan. 5: Describe molecular genetic responses, facilitating survival & adaptation in pest insects by identifying lygus & whitefly transcripts responsive to xenobiotics & environmental (thermal, water, oxidative) stressors, identify molecular targets for disruption by chemical or genetic agonists or antagonists, & develop methods to deliver dsRNA for functional disruption of aquaporins or other targets essential to maintain homeostasis. Sub-objective 5A through 5B: See uploaded project plan. Sub-objective 5C: Examine the potential of an ornamental plant to disrupt the osmotic water permeability of B. tabaci aquaporin water channel proteins using cage studies and in vitro heterologous insect cell expression functional assays.(New, May, 2018)
Interactions among key prey and predator species will be quantified using molecular marking and gut content assays in laboratory, greenhouse and field experiments. Meta-analyses of updated databases will examine the impacts of transgenic Bt crops on non-target arthropod abundance, community diversity, and biological control services. Insecticide susceptibility of whitefly in relation to host and environmental conditions will be determined using laboratory assays of field-collected insects. Results of field studies will guide controlled experiments to determine mechanisms by which host condition, population density, and temperature influence susceptibility to insecticides, including expression of detoxification enzymes. Inheritance, dominance, and allelism of Cry2Ab resistance in the pink bollworm will be determined using crosses among laboratory strains of the insect. Roles of pink bollworm cadherin and ABC transporter protein as functional receptors of Cry-toxins will be examined by fluorescent imaging of cell cultures transfected with tagged clones of the target cDNA. Cytotoxicity of Cry-proteins will be determined for each putative receptor. Seasonal patterns in whitefly sex ratios will be documented in the field and association of symbionts with sex ratio shifts will be examined using PCR. Respective roles of male availability and copulation interference in determining sex ratios will be evaluated in greenhouse studies. Potential insect- and plant-derived semiochemicals for manipulating or monitoring whitefly will be identified by GC and screened using olfactometry. Attractiveness of the recently identified sex pheromone of Lygus hesperus will be optimized using electro-antennographic detection followed by field trap studies and experiments to determine the diel pattern of pheromone emission. Influences of male lygus reproductive phenology, time since mating, and concentration of a chemical inhibitor of mating on mating frequency will be determined in laboratory assays. Also, potential of the mating inhibitor as a mating disruptant will be evaluated based on responses of insects to treated substrates. Influences of environmental extremes on development and survival of lygus and selected predators, and on mating, reproduction, and longevity of lygus adults, will be examined in controlled studies incorporating constant and variable temperature regimes. Stage-specific sensitivity of the lygus diapause response will be examined in photoperiod-switching and controlled environment experiments. Companion studies will examine hemolymph protein and transcript profiles to identify potential molecular markers indicative of diapause. Molecular responses of whitefly and lygus to xenobiotic and environmental stressors, especially temperature, will be assessed based on transcriptomic responses to experimentally induced stress, and links between stress responses and susceptibility to insecticides will be examined in bioassays. dsRNA will be used against selective targets to silence genes important to biological fitness in lygus and whitefly.