播种时间对棉田害虫和天敌种群的影响

通过对3种不同时间播种的棉田内害虫、天敌系统调查，分析和比较了播种时间对棉田害虫、天敌种群和群落的影响。结果表明，播种期推后，可减轻或避免第二代棉铃虫的为害，加重第三代和第四代棉铃虫的为害；但不同播种日期对不同时期的棉蚜影响不同，苗蚜以迟播棉田内种群数量最高，伏蚜则以夏播棉田内种群数量最高。播种期的推后，不利于棉田捕食性瓢虫、蝽类、蜘蛛和寄生性天敌种群增长。棉田害虫和天敌群落多样性指数也随播种期的推后而下降．因此．应针对不同时间播种的棉田开展相应的害虫生态管理。

Effect of planting-date on the population dynamics of pest and its natural enemies in cotton agroe-cosystem

The population dynamics of pests and natural enemies from 3 types of cotton field, in which cotton seeds were sowed on April 27, May 15 and June 15 of 2000, were investigated and compared, respectively. The less number of 2nd generation cotton bollworm ( Helicoverpa armigia ) and more number of 3rd and 4th generation cotton bollworms were observed in late sowed cotton than in early sowd cotton. The greatest population of seedling aphids ( Aphis gossyppi ) and summer aphids were found in cotton field in which cotton seeds were sowed on May 15 and June 15, respectively. With the delay of planting date, population number of natural enemies and community diversity index of pests and their natural enemies were decreased. The pest management strategies for 3 types of different sowting date for cotton agroecosystem were also discussed in this paper.