生态恢复状态下天敌对小菜蛾的自然控制作用

通过组建不同防治措施下的小菜蛾自然种群生命表，结果表明，化学防治区小菜蛾自然种群趋势指数为52.52；在生态恢复区，天敌因子对目标害虫的自然控制作用得到恢复和增强，连续4个世代的小菜蛾种群趋势指数分别为16.9、7.16、3.71和4.02，其种群数量的发展得到有效地抑制.影响小菜蛾春季第一、第二、第三及第四代种群数量的重要因子分别为绒茧蜂寄生、4龄幼虫的捕食及其它、赤眼蜂寄生和绒茧蜂寄生，其相应的排除作用控制指数分别为1.39、1.56、1.74和1.54.从天敌与小菜蛾种群相互作用的过程来看，前者对后者的控制作用表现出明显的时滞效应，其种群数量的发展需要一个累积过程.能否采取积极的田间保护、增强措施，将是充分发挥天敌控害潜能的关键因素之一.

Control effect of natural enemies on Plutella xylostella under ecological restoration condition

A field study on the life table of diamondback moth(DBM)Plutella xylostella showed that the population increase index of DBM in chemical control plot was 52.52,while that of four continuous generations of DBM in ecological restoration plot was 16.9,7.16,3.71 and 4.02,respectively,indicating that the control effect of natural enemies on target pest was greatly improved.The main factor affecting the first and forth generations of DBM was the parasitism of Cotesia plutella,while those affecting the second and third generations of DBM were the predator of the 4 th instar larva and the parasitism of Trichogramma,with the corresponding exclusive index of population control(EIPC)being 1.39,1.54,1.56 and 1.74,respectively.There was an obvious time lag effect of natural enemies on their target pest,and thus,to protect and multiply the population of natural enemies in the field should be the key point of fully exerting the potential of natural enemies in their pest control.