What we have learnt on impacts of Bt cotton on non-target organisms in China

Abstract Bt transgenic cotton, containing a Bacillus thuringiensis toxin gene, has been widely planted in cotton growing areas in China since 1997. One of the major concerns of environmental risk is the impact on non-target organisms in the agriculture ecosystem. Results obtained in recent years indicate that the predator levels in Bt cotton fields are significantly higher than those in conventional cotton fields where insecticide has been used for control of the cotton bollworm, Helicoverpa armigera . However, the population density of parasitic wasps which parasitize on H. armigera larvae decreases dramatically due to the lower density and poor quality of H. armigera larvae in Bt cotton fields. As the predator population increases, the outbreak of cotton aphid [ Aphis gossypii ] in mid-season is effectively controlled, while the mirids become key insect pests in Bt cotton fields because of a reduced number of insecticides used against H. armigera . The diversity of the arthropod community in Bt cotton fields is higher than that in conventional cotton, suggesting that Bt cotton is highly favourable for integrated management of cotton pests. An assessment on the impact of Bt cotton pollen on two important economic insects, the Chinese tussah silkworm, Antnaea perngicuerin [ Antheraea pernyi ] and the silkworm, Bombyx mori , was conducted, from which it was concluded that the adverse effect is negligible.