Increased tolerance of fall armyworms (Lepidoptera : Noctuidae) to Cry1Ac delta-endotoxin when fed transgenic Bacillus thuringiensis cotton: Impact on the development of subsequent generations

Increased tolerance to Cry1Ac protein was found in a population of fall arm yworms, Spodoptera frugiperda (J. E. Smith), after selection for a single g eneration with transgenic Bacillus thuringiensis Berliner (Bt) cotton folia ge. When fed Cry1Ac treated artificial diet, larvae whose parents had fed o n transgenic Bt cotton leaves had significantly higher larval weights and a shorter time to pupation than those larvae whose parents had fed on conven tional cotton leaves. In addition, there was no evidence to suggest any fit ness or vigor differences existed from progeny of fall armyworms that fed p reviously on conventional or transgenic Bt cotton. Furthermore, tolerance o f fall armyworms to Cry1Ac had a heritable component in the subsequent gene ration based on larval weights and time to pupation. These data show that u sing a common approach designed to control all intrinsically tolerant lepid opteran species of transgenic Bt cotton identically may not be desirable.