Transgenic Bt (Bacillus thuringiensis) cotton has been effectively used to control the cotton bollworm,
Helicoverpa armigera (Hübner) in China. However, in recent years, following the wide commercialization
of Bt cotton in northern China there have been frequent outbreaks of the non-target pest Apolygus
lucorum (Meyer-Dür). To clarify how transgenic cotton contributes to these outbreaks, a four-year field
investigation of population dynamics and laboratory life table studies were carried out from 2007 to
2010 to evaluate the impact of two transgenic cotton cultivars (SGK321 expressing Cry1Ac þ CpTI and
GK12 expressing Cry1Ac) and their corresponding parental non-transgenic lines (Shiyuan321 and
Simian3) on A. lucorum. There were no significant differences in the population densities of A. lucorum
found in Bt cotton and non-Bt cotton plots, whether one compared those that had received insecticide
treatments or those that had not. However, population densities of A. lucorum were significantly lower in
pesticide treated plots than in controls. Furthermore, there were no significant differences in the net
reproductive rates, generation times or intrinsic rates of increase of A. lucorum when reared on either Bt
or non-Bt cotton cultivars. These results suggest that Bt cotton has no direct positive or negative effects
on the biology of A. lucorum, so the most logical explanation for the observed outbreaks is the decrease in
pesticide applications following the commercial release of Bt cotton.