Evaluating susceptibility of the western corn rootworm (Diabrotica virgifera virgifera LeConte) to Bt corn through application of an F1 screen

The western corn rootworm (Diabrotica virgifera virgifera LeConte) is a major pest of corn in North America. Genetically modified corn that produces insecticidal proteins from Bacillus thuringiensis (Bt) provides effective control of western corn rootworm, however, appropriate resistance management strategies are needed to ensure long-term durability of Bt corn. We applied an F1 screen to measure the standing level of genetic variation for survival of western corn rootworm on Bt corn. We tested the F1 progeny of adults collected from four treatments: 1) a single trait event with Cry3Bb1 (YieldGard VT Triple), 2) a pyramided event with Cry3Bb1 and Cry34Ab1/35Ab1 (SmartStax), 3) the pyramided event with a blended non-Bt refuge and 4) a near isogenic line that did not contain a Bt trait. Progeny from each family were evaluated on three corn types: a pyramided event (SmartStax) producing Cry3Bb1 and Cry34/35Ab1, a single trait event (YieldGard Vt Triple) producing Cry3Bb1, and a near isogenic non-Bt hybrid. We collected data on larval survival and instar after 17 days of exposure. Our results address the added durability derived from pyramiding multiple Bt toxins that target the same pest.