Fitness costs of Bt resistance in western corn rootworm

Resistance of insects to transgenic crops producing insecticidal toxins from Bacillus thuringiensis (Bt) has the potential to cut short the benefits these crops provide. Bt corn provides effective control of western corn rootworm, Diabrotica virgifera virgifera Le Conte (WCR), which is a significant pest of corn. Fitness costs arise in the absence of Bt toxin when insects that harbor Bt resistance alleles have lower fitness than Bt-susceptible insects. Fitness costs are important because they can delay or prevent the evolution of Bt resistance. We tested for the presence of fitness costs using a WCR strain that had been selected in the laboratory for Bt resistance. We reared Bt-resistant and Bt-susceptible insects on three corn hybrids and measured their survival to adulthood, longevity, fecundity, and egg viability. These data address the extent to which fitness costs of Bt resistance may be present in WCR and whether certain non-Bt corn hybrids can magnify fitness costs.