Resistance Effects of Transgenic Bt Cotton on Helicoverpa armigera in the Cotton Fields

The effects of transgenic Bt cotton on resisting Helicoverpa armigera were studied.The results showed that compared with routine cotton fields,numbers of the survival larvae of every generation de- creased by 81.82%—100.00%,and the difference was obviously significant.The damage rate of buds and leaves of cotton decreased by 92.30%—100.00% in the 2nd generation,and the difference was sig- nificant;the damage rate of mature bolls,young bolls,buds and flowers of cotton reduced by 35.43%—100.00% in the 3rd and 4th generations,and the differences were significant and obviously significant, respectively.The resistance of transgenic Bt cotton to Helicoverpa armigera is the 2nd generationthe 3rd generationthe 4th generation in transgenic Bt cotton fields.But the numbers of the survival larvae of the 3rd and the 4th generations H.armigera increased in the cotton fields.Then the damage rate of the cotton organs increased.So we must control H.armigera in time.