江苏沿海棉区常见捕食性天敌在Bt棉田的消长动态与分布

以常规棉为对照,对江苏沿海地区Bt棉田捕食性天敌种群消长动态进行了系统调查,结果表明:捕食性天敌主要涉及6个科共16个常见种。两类棉田内6类天敌的种群数量均表现为蜘蛛类>瓢虫类>草蛉类>捕食蝽类>捕食螨类>食蚜蝇类,其中前2类分别占天敌总量的78%～79%和19%～20%。与常规棉比较,Bt棉田内蜘蛛类、瓢虫类、捕食蝽类和天敌总量分别增加78.26%、61.91%、114.28%和73.85%,草蛉类和捕食螨类分别减少2.78%和14.29%。捕食螨类和食蚜蝇类主要在棉花生长前期发生,其他4类天敌则主要在棉花生育中后期发生。面上普查结果表明,Bt棉田捕食性天敌总量比常规棉田增加25.63%～47.50%。

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:spiders>ladybird beetles>green lacewings>predacious stink bugs>predacious mites>syrphids.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.