Emergence of adult Diabrotica virgifera virgifera LeConte from volunteer Bt corn in fields of commercial soybean (Glycine max)

Transgenic volunteer corn expressing herbicide resistance (HR) traits is a significant problem weed in corn/soybean rotational systems. This issue is particularly timely due to the increasing prevalence of stacking both herbicide and insect-resistant (mainly B.t.) traits into the same genetically-modified plant. Collection and analysis of volunteer corn plants from Indiana soybean fields indicate that volunteer corn plants testing positive for B.t. may sustain significant damage due to western corn rootworm (WCR) (Diabrotica virgifera virgifera) feeding. We placed emergence traps over volunteer plants expressing the insecticidal protein Cry3Bb1 and volunteer plants not expressing Cry3Bb1 in 2008 to determine the average number of WCR beetles emerging from HR/B.t. corn plants under natural infestation conditions. Our data indicate that these plants may support development to the adult stage under field conditions. Furthermore, we found that these corn plants also express a high level of resistance to glyphosate (i.e. Round-up®), indicating that glyphosate-only herbicide applications (a common weed management practice in glyphosate-resistant soybean) will have little or no effect. Volunteer corn plants stacked with both HR and insect resistant traits have the potential to impose additional, unforeseen selection pressure upon western corn rootworm (WCR) populations.