Abstract: Systematic investigations were carried out on the effect of transgenic Bt cotton on the population dynamics of non-target pests and natural enemies of pests in Hubei province in 2000-2001.This experiment included three treatments. The first was a transgenic Bt cotton field that utilized pesticides to control pests (FPC), the second was a transgenic Bt cotton field that used natural enemies to control pests (FNEC), and the third was a normal cotton field that adopted IPM (integrated pest management) to control pests (FIPM). The results showed that the population densities of non-target pests in transgenic Bt cotton fields were obviously increased. The cumulative and peak numbers of aphids in FPC and FNEC increased by 37.9% and 71.4%, respectively, than those recorded in FIPM in 2000 and by 92.5% and 134.9% than those recorded in FIPM in 2001. Cumulative and peak numbers of red spider mites in FPC and FNEC increased by 181.1% and 298.3%,respectively, than those recorded in FIPM in 2000 and by 69.9% and 105.0% than those recorded in FIPM in 2001. Transgenic Bt cotton had no obvious resistance to Prodenia infecta and tobacco whitefly, which have become more serious pests of cotton in recent years. Populations of natural enemies was also significantly higher in transgenic Bt cotton fields. Cumulative and peak values of spiders in FPC and FNEC increased by 66.3% and 112.1%,respectively, than those recorded in FIPM in 2000 and by 95.1% and 111.7% than those recorded in FIPM in 2001. Cumulative and peak values of Propylaea japonica in FPC and FNEC increased by 140.8% and 135.4%,respectively, than those recorded in FIPM in 2000 and by 67.2% and 109.5% than those recorded in FIPM in 2001. An important natural enemy in transgenic Bt cotton fields, Geocoris pallidipennis was almost absent in normal cotton fields. These results suggest that optimizing the utilization of natural enemies in transgenic Bt cotton would be a valuable addition to the existing IPM techniques.

Key words: transgenic Bt cotton, non-target pests, natural enemy, population dynamics