Location: Crop Protection and Management Research2012 Annual Report
1a. Objectives (from AD-416):
Determine effects of landscapes on population growth of major pests, stink bugs in Bt cotton. Conduct research to understand why stink bugs are important pests on Bt cotton.
1b. Approach (from AD-416):
1) Sample stink bug populations at the landscape level to confirm sequence of habitats used. 2) Estimate net reproductive rate and inter-patch movement, parametize and fit model using data to predict colonization of cotton and effects of landscape structure on colonization.
3. Progress Report:
This is the final year of a study of the effects of landscapes on stink bug populations in southern Georgia. This project was related to objectives 1A, 1B and 1D of the inhouse project: (1A) Study the role of landscape make-up on populations of stink bugs; (1B) Evaluate semi-field bioassays for the effects of relative crop quality on major crops used simultaneously by stink bugs; (1D) Assess survival of stink bug egg masses in soybean, cotton, and peanut. All of the field data in the regional analysis and most of the data for parameterization of the model predicting stink bug populations in cotton have been collected. Stink bug populations were found not to originate from the woodland adjacent to four major crops grown in the region, regardless of the landscape. There were also competitive interactions between heliothine larvae and stink bugs that were species dependent; fourth instar H. zea reduced growth rates of both stink bug species by 60% when caged on a single cotton boll and reduced growth rates of only E. servus by 36% when caged on a cotton branch. In contrast, H. virescens had no effect on stink bug growth rates. Resource competition was apparent in the interactions between H. zea and E. servus, but interference competition contributed to the interactions as well. Competitive release of stink bug populations in Bt cotton is possible, and should be more likely for E. servus than for N. viri-dula. Additionally, prior H. zea feeding inhibited, whereas H. virescens feeding facilitated, E. servus feeding on damaged plants. Caterpillar feeding did not affect N. viridula feeding behavior. Caterpillar herbivory caused an overall reduction in phenolic concentration with a particularly strong reduction in chlorogenic acid in bolls from plants damaged by H. virescens. Euschistus servus preference was strongly influenced by host selection and host edibility but phenolics did not likely influence plant choice. Stink bugs prefer to oviposit on undamaged cotton over cotton damaged by heliothine larvae.