Assessing western corn rootworm resistance to Bt corn in the landscape

Western corn rootworm (Diabrotica virgifera virgifera) is a pest of concern to farmers in the Midwest. The ability of western corn rootworm (WCR) to develop resistance to transgenic Bt corn is of particular scientific and practical interest. Resistance to Cry3Bb1 corn and mCry3A corn is already present in some field populations. Integrated pest management practices may help to delay further evolution of resistance and may act to reduce the abundance of WCR within fields. These practices include scouting of western corn rootworm populations, crop rotation, and rotating modes of action against WCR. Continued research on WCR is necessary to assess the effectiveness of these approaches at mitigating the consequences of resistance in the field. Additionally, little is known about the correlations in the level of resistance among populations within the landscape. We will study fields with a history of injury to Cry3Bb1 corn to quantify WCR abundance, root injury, survival on Cry3Bb1 corn and the frequency of resistance alleles. These data will also be collected from surrounding fields to quantify the prevalence of resistance at the landscape level and the consequences for WCR abundance and feeding injury to corn.