Effects of chemical insecticides on populations of insect pests and natural enemies in different cotton fields
化学杀虫剂对不同类型棉田害虫、天敌种群的影响

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...