Field and laboratory performance of transgenic Bt cotton containing Cry1Ac against beet armyworm larvae (Lepidoptera: Noctuidae)

The efficacy of transgenic Bt cotton genotype containing Cry1Ac was investigated against beet armyworm, Spodoptera exigua (Hubner) in the field and laboratory experiments. The results showed that S. exigua larvae had low susceptibility to Bt. cotton. No significant differences in larval densities between transgenic Bt. and conventional cotton under unsprayed conditions were observed and insecticides were used to control the population in sprayed Bt. and non-Bt cotton plots. The laboratory bioassays showed no significant impacts of Bt. cotton plant structures (leaves and flower-bolls) on the larval mortality as compared to conventional non-Bt cotton. However, the results indicated sublethal effects with significant differences in larval development time and pupal weight.