Location: Vegetable Crops Research
Project Number: 5090-21220-006-023-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 30, 2019
End Date: Jun 29, 2023
Objective:
Objective 1. Compare the emergence phenology of select Colorado potato beetle populations representing field sites previously documented as neonicotinoid-resistant or susceptible.
Objective 2. (A) Characterize and compare the unique fatty acid profiles of select Colorado potato beetle populations representing field sites previously documented as neonicotinoid-resistant or susceptible. (B) Identify potential fatty acid targets in the pesticide detoxification pathway(s) that encode for heightened resistance for ribonucleic acids (RNA) interference (RNAi).
Objective 3. Compare the fatty acid composition of multiple cultivars of Solanum tuberosum for differential dietary sources of fatty acid compositions that could influence insect fitness or resistance potential.
Approach:
Objective 1. We will monitor emergence patterns at six field locations; three previously classified as neonicotinoid-resistant populations, and three classified as susceptible. Beginning after the first recorded adult has been observed to emerge and colonize the potato crop, all adult Colorado potato beetles (CPB) will be counted and collected directly into plastic cups every week over four successive weekly intervals. To compare emergence patterns for each population, a nonlinear regression analysis will be used to fit three-parameter logistic regression growth curves to cumulative CPB counts over time. Bioassay dose–response assessments will be performed on sets of 350 adult CPB collected weekly and analyzed against imidacloprid concentrations with a Log10 probit regression analysis. LD50 estimates and 95% CIs will be calculated to determine relative neonicotinoid susceptibility of these weekly, field-collected populations.
Objective 2. (A) Using CPB and potato foliage collected in Objective 1, we will uncover the fatty acid composition associated with both insecticide susceptible and resistant phenotypes. We will examine the fatty acid profiles of four replicates from six insect populations at four time points, resulting in 96 insect samples. We will also examine the lipid composition of potato foliage that the insects are feeding on to standardize insect fatty acid composition between cultivar and location. Total fat content of insects and potato foliage will be extracted using published best management practices.
Objective 3. We aim to compare the fatty acid composition of cultivars of Solanum tuberosum for differential dietary sources of fatty acid that could influence insect fitness or resistance potential. Using fatty acid analysis outlined in Objective 2 we will examine the relative fatty acid composition of six different potato cultivars to determine relative fatty acid composition. We will then perform a randomized choice assay to determine CPB feeding preference. Using 20 replicate sets of adult Colorado potato beetles from both an insecticide resistant and susceptible lab populations, we will determine if insects prefer to consume certain potato cultivars. We can relate the insects feeding preference back to the fatty acid composition of potato cultivar to determine if there are underling fatty acids that are insect attractants or repellents. By the completion of this objective, we will be able to determine the relative importance of fatty acids to insect dietary preferences, which could be incorporated into potato breeding programs.
