自然天敌对苗蚜和伏蚜控制作用的定量分析

Effects of suppression of natural enemies on cotton aphids

【目的】为了合理利用自然天敌,定量评价棉田自然天敌对苗蚜和伏蚜的控制作用。【方法】采用接虫罩笼法结合系统调查。【结果】发现苗蚜的主要自然天敌是龟纹瓢虫Propylaea japonica Thunberg和异色瓢虫Harmonia axyridis Pallas,大部分时间能够有效的控制苗蚜种群在防治指标以下,控害指数高达91%;伏蚜主要自然天敌是蜘蛛、草蛉和龟纹瓢虫,由于其种群数量太少,益害比低,对伏蚜控害指数始终低于20%,无法有效的控制伏蚜种群。【结论】结果提示,应根据苗蚜和伏蚜自然天敌控制作用不同,制定合理的保护利用自然天敌的策略。

[Objectives] To evaluate the effects of suppressing natural enemies on cotton aphids on cotton seedlings and during summer. [Methods] Field investigations and enclosures. [Results] Propylaeajaponica and Harmonia axyridis were the main natural enemies of aphids during the cotton seedling stage and could effectively suppress the aphid population achieving a biocontrol services index （BSI） 〉 91%. Araneae, Chrysopidae and Propylaeajaponica were the main natural enemies of aphids in summer. These predators could not effectively suppress the population of summer aphids; because of low population densities and low natural enemy to aphid ratio the BSI was always 〈 20%. [Conclusion] The results indicate that the effectiveness of natural enemies to control aphids in cotton fields varies between the seedling stage and summer.