Research Accomplishment Reports 2009

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

J. White
Department of Entomology

 

Non-Technical Summary

The planting of transgenic corn in the United States has increased dramatically since the mid-1990s. However, the widespread planting of Bt-corn throughout the United States means that many non-target arthropods are exposed to endotoxin proteins which were initially designed to restrict pest populations. Feeding on the abundant components of the detrital food chain could increase the likelihood of uptake of Bt-endotoxins by predator communities. We propose to quantify, for the first time, the interaction pathways between transgenic insecticidal crops expressing Cry1Ab and Cry3Bb1-endotoxins and the non-target arthropod food web.

Using antibody-based quantitative technology (which has already been developed and optimized) for the detection of these proteins in invertebrates, we will test the hypothesis that transgenic endotoxins flow through the arthropod food chain. These interaction pathways are predicted to 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.

2009 Project Description

In this first year of participation in NC-205, we collected European corn borers from two locations (MN and KY), evaluated parasitism by Macrocentrus grandii in both locations, determined the flight period for Macrocentrus in KY, and evaluated both populations for presence of a Wolbachia, a bacterial symbiont that could be responsible for recently observed biased sex ratios in this species.

2009 Impact

Change of knowledge: We found that M. grandii parasitism of overwintering European corn borer larvae was approximately 10% in a collection from Lexington Kentucky, but 0/320 larvae collected in Rosemount, MN were parasitized. This absence of parasitism at the MN location is particularly surprising, given that the Rosemount location had consistent levels of 10-20% parasitism during the first half of the decade.

In Kentucky, we outplanted European corn borer larvae weekly from June to mid-August, and returned the larvae to the lab after 1 week of exposure to field parasitism. We recovered M. grandii parasitoid broods from the larvae outplanted between July 29 and August 12, probably corresponding to the second generation flight period of the parasitoid.

Finally, we have not found evidence of the presence of Wolbachia in our initial survey of MN-collected European corn borers, but will conduct a more thorough survey in the coming year using DGGE (Denaturing Gradient Gel Electrophoresis), which may uncover the presence of other bacterial symbionts capable of reproductive manipulation.