Corn Rootworm (Diabrotica spp.) and Bt Corn: Effects on Pest Survival, Emergence and Susceptibility

The northern and western corn rootworm (Coleoptera:Chrysomelidae) are major pests of corn (Zea mays L). The development of Bt corn, corn that has been genetically modified to produce toxins from Bacillus thuringiensis, has been valuable in controlling the damage these pests can inflict on a grower’s corn. With the large acreage being planting to Bt corn especially in the Midwest, there has been great selection pressure for these pests to adapt and overcome the effects of Bt toxins. The refuge strategy, as mandated by the EPA, helps maintain the susceptibility of the pest population to Bt toxins, thereby ensuring the continued success of this management strategy. This field experiment tested the interaction of northern and western corn rootworm beetles with Bt corn. Data were collected on beetle emergence time, survival and beetle size. We tested two hybrids of corn used to control corn rootworm: YieldGard VT Triple, a single-toxin hybrid producing the toxin Cry3Bb1 and SmartStax, a pyramided toxin hybrid producing Cry3Bb1 and Cry 34/35Ab1. The study was conducted at two field sites for two years. Each site contained 16 plots composed of four treatments: pure stands of YieldGard VT Triple and SmartStax, SmartStax with approximately 5% blended non-Bt corn as a refuge and