化学防治对不同类型棉田害虫和捕食性天敌群落多样性的影响

分析比较了化学防治对8种不同类型棉田害虫、捕食性天敌群落多样性的影响。研究结果表明，化学防治对棉田害虫、捕食性天敌群落的多样性指数、均匀性指数、丰富度及个体数的变化有较大的影响，尤其对捕食性天敌群落的影响显著。但这种作用依不同类型棉田或棉花不同生育阶段而异：化学防治对套作棉田害虫、捕食性天敌群落的影响较小，而对单作棉田和豆间棉棉田害虫、捕食性天敌群落的影响较大；晚播棉田害虫与捕食性天敌群落较早播棉田受化学防治的影响更大；化学防治对免耕棉田害虫、天敌群落的影响更大，非免耕棉田害虫、捕食性天敌群落受其干扰较小；春套棉边害虫、捕食性天敌群落与其它棉田类型相比，受化学防治的影响较少；棉花害虫在棉花生育前期对化学防治较棉花生育后期敏感，而捕食性天敌在棉花整个生育期均对化学防治敏感。

Effects of chemical control on diversity of insect pests and predatory natural enemy communities in cotton fields under different cultivating regimes

Effects of chemical control on diversity of insect pests and predatory natural enemy were investigated in 8 types of cotton fields in Raoyang County, Hebei Province in 1999. The results showed that chemical control affected diversity and homogeneity indices, richness and the numbers of pests and predators in different types of cotton fields. Chemical control had a more significant effect on the diversity of predator than pest communities. The effects of chemical control differed in different types of cotton fields and in different stages of the growing cycle: the effects were more prominent in cotton monocultures or cotton bean intercropped fields than in those with cotton wheat intercropping, in late sown than early sown fields, and in untilled fields than tilled fields. The effect was less on the edges of intercropped cotton fields than in the middle. The insect pest community was more sensitive to chemical insecticides at the early stage of the growing cycle, while chemical control significantly influenced the insect predator community throughout the growth period of cotton plants.