Abstract: Transgenic cotton line R93-4 expressing Bacillus thuringiensis CrylA genewas used for evaluating the effects of Bt cotton on the survival and growth of different instar larvae of the cotton bollworm, Helicoverpa arrnigera (Htibner). Significant insecticidal activity of Bt cotton leaves was observed only on the first instar larvae successively feeding for 3 days. No larva could survive to pupation when fed on Bt cotton leaves continuously starting at 1st, 2nd, 3rd or 4th instar. But started feeding on Bt cotton leaves at fifth instar, larvae could normally survive to pupae. The inhibition effect of Btcotton on the growth of larvae was more obvious than the lethal effect. The mortality and growth inhibition of larvae by Bt cotton were higher at 28℃ as compared with 25℃. The results are valuable for further research on the monitoring and management techniques of the pest resistance to Bt cotton.

Key words: transgenic Bt cotton, Helicoverpa armigera, host plant resistance