Abstract：Transgenic cotton expressing the Cry1Ac toxin from Bacillus thuringiensis has been widely planted in China since 1997, which reached to 70% of the total cotton area in 2006.The monitoring results on environmental impacts of Bt cotton commercialization indicated that the target pests, cotton bollworm and pink bollworm were effectively controlled while the mirids evolved to be key pests in cotton system. There were no significant changes in resistance gene frequency of field populations of cotton bollworm, but a shift toward tolerance increase was apparent in the intensive planting area of Bt cotton, indicating that potential resistance risk from the target pest has become a major threat for sustainable planting of Bt cotton. In consideration of the factors associating with the resistance evolution, a risk management strategy is discussed in this paper.
