Research Accomplishment Reports 2007

Ecology and Management of European Corn Borer and Other Lepidopteran Pests of Corn

J. Obrycki
Department of Entomology

 

Project Description

Beginning in 1995, the use of Bt-transgenic corn for pest suppression has increased significantly in the United States. The widespread planting of Bt-corn results in the exposure of non-target arthropods to Bt endotoxin proteins which were designed to reduce pest populations. Feeding on components of the corn agroecosystem food web could increase the likelihood of uptake of Bt-endotoxins by predator communities.

In this project we document and quantify the pathways between transgenic insecticidal crops expressing cry1ab and cry3bb1-endotoxins and the non-target arthropod food web. Using antibody-based quantitative technology we have tested the hypothesis that transgenic endotoxins flow through the arthropod food chain. These interaction pathways will likely include significant flow through the detrital food web to carabids (by consumption of molluscs and annelids) and Araneae (through the consumption of collembola). These species are major food resources for generalist predators in corn agroecosystems. Many generalist predators are exposed to Bt-endotoxins from transgenic corn through direct consumption of plant material and feeding on herbivorous and/or detritivorous prey. These endotoxins can be taken up by herbivores, detritivores and arthropod predators, but there is little understanding of the mechanisms associated with their movement into higher trophic levels. Slugs and earthworms, important components of the carabid food chain, could provide important linkages between Bt-containing plants and these predators, given their uptake of such proteins. In this study we will determine the significance of Bt endotoxin linkages   between Bt-corn and arthropod predators. 

Impact

Using an enzyme-linked immunosorbent assay, the uptake of Bt endotoxins by predatory coccinellids and the importance of anthesis to this trophic pathway was examined. Adult Coleomegilla maculata, Harmonia axyridis, Cycloneda munda, and Coccinella septempunctata contained detectable quantities of Bt-endotoxin when screened by ELISA. Thirteen percent of 775 adult C. maculata tested positive for Bt-endotoxins. The presence of Bt-endotoxins in the guts of adult coccinellids was not confined to periods around anthesis. These field studies present the first evidence for temporal variability in Bt-endotoxin uptake in coccinellid food chains and the lack of a direct correlation between anthesis and Bt-endotoxin concentrations in predator guts.

Publications

Harwood, J.D. & J.J. Obrycki. 2007. Temporal detection of Cry1Ab-endotoxins in coccinellid predators from fields of Bacillus thuringiensis corn. Bulletin of Entomological Research 97: 643-648.