化学杀虫剂对不同类型棉田害虫、天敌种群的影响

研究了化学杀虫剂对6种不同类型棉田的害虫、天敌种群数量及其相互作用的影响。结果表明，化学防治使棉花苗期棉蚜数量下降，但不能抑制中后期棉蚜数量；除豆间棉田外，其他类型棉田化防区棉红蜘蛛和棉铃虫数量低于未防区。化学防治使各类型棉田天敌数量减少，以单作棉田天敌数量减少最明显，间套作棉田天敌数量下降幅度较小；此外，棉田不同天敌种群所受的影响存在一定差异，化学防治对瓢虫、捕食蝽类的影响显著，数量下降剧烈，但蜘蛛类群下降幅度比前两者小。化学防治对棉田害虫与天敌的相互关系的影响随棉田类型或害虫、天敌种类的不同而有所差异。

Effects of chemical insecticides on populations of insect pests and natural enemies in different cotton fields

Effects of chemical insecticides on populations of insect pests and natural enemies in 6 types of cotton field were studied in Raoyang County, Hebei Province, China in 1999. The cotton field types included: spring-planting cotton (planted on 27 April), late-planting cotton (planted on 15 May), summer-planting cotton (planted on 15 June), cotton-wheat intercropping in spring (planted on 27 April), cotton-bean intercropping (planted on 27 April), and cotton-wheat intercropping in summer (planted on 30 May). T...