Susceptibility of European and Asian corn borers (Lepidoptera: Crambidae) to Bacillus thuringiensis toxins

Comparative susceptibility of the European, Ostrinia nubilalis (Hübner) and Asian, Ostrinia furnacalis (Guenée) corn borer neonates was determined for six different toxins from Bacillus thuringiensis. Susceptible populations of European and Asian corn borers originated from northern Italy and Tanjung Karang, Malaysia, respectively were used in all bioassays. Corn borer larvae were exposed to artificial diet, surface-treated with increasing concentrations of Bt toxin. Each toxin (Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba, Cry1F and Cry2a) was prepared from fermentation of transformed Escherichia coli, except for Cry1F which was supplied as purified crystals from Dow AgroSciences, Indianapolis, IN. Mortality and growth inhibition were evaluated after 7 days. The range of variation in Bt susceptibility indicated by growth inhibition was similar to variation indicated by mortality. Importantly, both species exhibited similar sensitivity to all 6 toxins suggesting shared toxin receptors and mechanisms of toxicity for both species.