Temporal And Spatial Dynamics of Transgenic Bt Cotton Toxins to Cotton Bollworm in North China

Transgenic Bt cotton line GK- 12 developed in China was used to test the temporal and spatial dynamics of Bt cotton toxins to the cotton bollworm, Helicoverpa armigera Hubner. Toxins of Bt cotton leaves to H. armigera decreased as crop maturation and significantly declined after flowering stage. The efficacy of deferent flower parts of Bt cotton was high in the period of third gen eration but declined in fourth generation of H. armigera in North China. In modeling natural condition, the survival rate of H. armitera in fourth generation was 0.4 %, and significantly higher than in second generation. The toxin order of Bt cotton organs was as fol- lowing: leavessquaresbollsflowers, maturated leavesyong leaves.