Screening field populations of western corn rootworm for susceptibility to Bt corn

The western corn rootworms Diabrotica virgifera virgifera is a major pest of corn in the United States that is currently managed by planting of corn that produces insecticidal toxins derived from the bacterium Bacillus thuringiensis. During the summer of 2009, we sampled western corn rootworm populations from several fields throughout Iowa. Some of these populations were collected from fields in which growers complained of poor performance of Bt corn, and others were from areas where Bt corn performed well. Eggs were collected from each population and then used to conduct laboratory bioassays. Neonate larvae from each population were assayed against two Bt hybrids, one producing Cry3Bb1 and another producing Cry34Ab1/Cry35Ab1. Larvae also were evaluated on the non-Bt near isogenic hybrid of each transgenic. Larval development and survival were recorded after 17 days. These data provide a measure of the variation in Iowa populations of western corn rootworm for survival and development on some of the current Bt transgenic technologies.