Location: Pest Management and Biocontrol Research
Project Number: 2020-30400-001-000-D
Project Type: In-House Appropriated
Start Date: Jul 1, 2025
End Date: Jun 30, 2030
Objective:
Objective 1: Expand existing knowledge of the major pests such as lygus bug, cotton seed bug, and whitefly in cotton and other relevant crop systems, and their natural enemies, by exploring fundamental aspects of their behavior, biology, and ecology. Emphasis will be placed on movement and feeding, biochemistry, molecular biology, and ecology of heat and drought stress.
Sub-objective 1A: Identify key predators within the cotton system and estimate ratios of predators to the western tarnished plant bug, Lygus hesperus, that provide sufficient suppression of pest populations to minimize chemical control.
Sub-objective 1B: Evaluate sesame as a beneficial intercrop for enhancing biological control services in cotton.
Sub-objective 1C: Identify the food plant host use patterns of the cotton seed bug, Oxycarenus hyalinipennis, in the ecological context of its invaded range in southern California.
Sub-objective 1D: Determine the efficacy of insecticides at different life stages of the cotton seed bug, Oxycarenus hyalinipennis.
Objective 2: Facilitate the design and implementation of new management approaches, such as genetic-based biocontrol, sterile insect release techniques, and the use of beneficial companion planting for control of cotton pest insects, including the cotton bollworm and cotton seed bug.
Sub-objective 2A: Develop genetic-based sterilization approaches for the western tarnished plant bug, Lygus hesperus.
Sub-objective 2B: Examine the molecular basis of sex differentiation in the western tarnished plant bug, Lygus hesperus.
Sub-objective 2C: Genetically engineer the western tarnished plant bug, Lygus hesperus.
Sub-objective 2D: Examine the molecular basis of sex differentiation in the cotton bollworm, Helicoverpa zea.
Sub-objective 2E: Genetically disrupt spermatogenesis in the cotton bollworm, Helicoverpa zea.
Objective 3: Preserve current transgenic Bacillus thuringiensis (Bt) insecticidal crop technology by determining resistance mechanisms in cotton bollworm, identifying genetic markers of resistance by machine learning, and enhancing biological control by better conservation of natural enemies.
Sub-objective 3A: Evaluate Arizona western tarnished plant bug, Lygus hesperus, field populations for susceptibility to the Bt toxin Cry51Aa2 and perform laboratory selection to evaluate potential for evolution of resistance.
Sub-objective 3B: Identify Vip3Aa Bt resistance mechanisms in the cotton bollworm, Helicoverpa zea.
Sub-objective 3C: Develop a machine learning approach to identify Bt resistance loci in the cotton bollworm, Helicoverpa zea.
Approach:
Objective 1: Biological control-informed thresholds, which determine pesticide treatment using the density of pests and their predators, will be developed for L. hesperus in cotton using experimental field research and data mining. Densities of L. hesperus and natural enemy communities will be manipulated and monitored to identify key predators of L. hesperus. Predictions of ratios that enable biological control will be tested and compared to conventional threshold models. To enhance the positive impact of reduced pesticide treatment regimes, companion plantings of sesame with cotton will be tested for desirable impact on the pest, natural enemy, and pollinator populations and on key cotton and sesame yield metrics. To improve predictions of the spread and potential threat of the invasive O. hyalinipennis, a gut content assay will be developed under lab conditions to reveal diet, then used on field caught insects to determine viable host plants at different life stages. O. hyalinipennis susceptibility to insecticides will also be tested at different life stages, using a panel of standard chemistries used to protect cotton.
Objective 2: CRISPR and RNAi will be used to screen a suite of genes in L. hesperus and H. zea to identify which are essential for sex determination and the fertility. Putative genes have been identified, and their functions will be confirmed knockout or knockdown. Once appropriate targets are identified they can be used as the basis for developing a genetic-based biocontrol strategy for these crop pests. One strategy is precision guided sterile insect technique. This approach will be validated by using CRISPR to create two independent transgenic lines with silenced target genes that when mated together produce only infertile male offspring.
Objective 3: Laboratory and field populations of L. hesperus will be tested for the capacity to evolve resistance to cotton engineered to express the Bacillus thuringiensis (Bt) toxin selective for this species using standard feeding assays. These will test for changes to susceptibility to Cry51Aa2 toxin over time with different exposure and selection regimes. Further, resistance mechanisms in H. zea to the Bt toxin Vip3Aa will be examined using genome-wide association studies (GWAS), fine-scale mapping, and RNA-seq. These will identify polymorphic genes with differential transcript abundance in field- and laboratory-selected Vip3Aa-resistant H. zea. Gene function will be confirmed using CRISPR knockout followed by toxicity screening. Existing genomic datasets for susceptible and resistant strains of H. zea will be used in a machine learning approach to train computer models to look for mutations that may confer resistance to Cry1Ac. If the models prove successful, they will be used on whole genome data available for a Vip3Aa-resistant strain (Vip3-R) relative to its susceptible parental strain (Vip3-S) to identify mutations possibly responsible for resistance.