Population Dynamics and Distribution of Common Predacious Natural Enemies in Transgenic Bt Cotton Fields in Jiangsu Provincial Coastal Area

The population dynamics of predacious natural enemies in transgenic Bt cotton and traditional cotton fields in Jiangsu provincial coastal area was systematically investigated. The results indicated that the predacious natural enemies mainly included sixteen common species in six families. Six families of natural enemies in two kinds of cotton fields were ranked by population density as follows:spidersladybird beetlesgreen lacewingspredacious stink bugspredacious mitessyrphids.The population density of spiders and ladybird beetles accounted for 78%～79% and 19%～20% of total natural enemies, respectively.In comparison with traditional cotton field, the population density of spiders, ladybird beetles, predacious stink bugs and total natural enemies in Bt cotton field was increased by 78.26%,61.91%,114.28% and 73.85%, respectively, while that of green lacewings and predacious mites in Bt cotton field was decreased by 2.78% and 14.29%, respectively. Predacious mites and syrphids broke out mainly at earlier growth stage of cotton, but the other four kinds of natural enemies broke out mainly at middle and later growth and development stage of cotton. The general investigation showed that the total density of natural enemies in transgenic Bt cotton fields increased by 25.63%～47.50% as compared with that in traditional cotton fields.