Abstract: Effects of transgenic cotton (cv. SGK321, with inserted genes of Cry1Ac and CpTI) on population dynamics of pests and natural enemies were studied in Nanpi County, Hebei Province in 2002. It showed that the composition of pest and predatory species was similar between the plots of transgenic cotton SGK321 and its parental line, sy321 cotton, but with different accumulated numbers for each species. From 24 surveys during May 23-September 16, the accumulated number of the main pest species decreased in SGK321, compared to those of sy321, by 89.5%, 64.5%, 21.8%, 15.6% and 33.7% for Helicoverpa armigera, Aphis gossypii, Lygus lucorum, Bemisia tabaci and Empoasca flavescens, respectively. For the main natural enemies, the accumulated numbers of Propylaea japonica and Chrysopa sinica increased by 34.0% and 9.1%, respectively during the same period; but those of Harmonia axyridis, Orius minutus, Campylomma diversicornis, Lysiphlebia japonica and spiders decreased by 28.6%, 6.5%, 43.1%, 44.7% and 14.0%, respectively. Population dynamics of the main pest and predatory species showed that the population peak of A. gossypii, E. flavescens and B. tabaci occurred from the middle to late July, late August to mid-September, and late August to early and mid-September, respectively. And the individual number of each pest species was lower in SGK321 plot than in sy321 during its peak period. The population peak of P. japonica lasted from the early July to middle and late August, and its number is higher in SGK321 plot than in sy321 during this period. The results suggested that the transgenic cotton SGK321 had control efficiency not only to the cotton bollworm, but also to some non-target pests, such as the cotton aphid and the tobacco whitefly. The individual numbers of P. japonica and C. sinica increased in SGK321 plot, compared to those in sy321, but those of other main natural enemy species decreased, indicating some negative effects of the transgenic cotton SGK321 on natural enemy populations.

Key words: Transgenic Cry1Ac+CpTI cotton, pest insects, natural enemy, population dynamics, safety evaluation