氰戊菊酯施用于寄主幼虫对菜蛾绒茧蜂的致死和亚致死效应

Lethal and sublethal effects of fenvalerate applied to host larvae on the parasitoid Cotesia plutellae

25℃下,分别在菜蛾绒茧蜂产卵寄生后的第1、3、5、7天(幼蜂分别处于卵、初龄幼虫、中龄幼虫、末龄幼虫期)将20％氰戊菊酯乳油1000倍水溶液以喷雾法施用于被寄生的小菜蛾幼虫。第1天和第7天处理使蜂的存活率明显下降,第1天处理导致育出雌蜂的产卵量低于对照,而第3天和第5天处理使蜂存活率下降幅度相对较小,且第5天的处理引起育出雌蜂的产卵量高于对照。不同时间处理均显著延长了该蜂卵+幼虫的发育历期,其中以第5天延长最为显著。除第3天外,其余时间处理导致育出蜂个体小于对照,且以第1天和第7天处理影响更为显著。羽化雌蜂的寿命均短于对照。对存活率和产卵量进行综合分析表明,氰戊菊酯施用于寄主幼虫对菜蛾绒茧蜂幼蜂的影响随后者发育阶段不同而变化,卵、末龄幼虫期较初龄、中龄幼虫期受到的不利作用更大。

The parasitized larvae of Plutella xylostella were sprayed with 1000 X water solution of 20% fenvalerate emulsifiable concentrate on the first, third, fifth, and seventh day (which corresponded to the egg, early larval instar, mid larval instar and last larval instar of the parasitoid respectively) , after oviposition by Cotesia plutellae at 25℃. Treatment on the first and seventh day caused substantial reduction of parasitoid survival, and the treatment on first day also resulted in reduction of adult fecundity compared to that of the control. However, treatment of the parasitized host larvae on the third and fifth day after oviposition by the parasitoid produced less adverse effect on the survival of the parasitoid, and treatment on the fifth day resulted in higher fecundity than that of the control. Treatment with fenvalerate increased the development duration of egg and larva, with treatment on the fifth day having the most significant effect. With the exception of treatment on the third day, treatment with fenvalerate reduced the size of resultant adult wasps, with more significant effects observed for the treatment on the first and seventh day. Treatment with the insecticide also reduced the longevity of the resultant adult wasps. Integrated analysis of both survival and fecundity indicated that toxicity of fenvalerate to the parasitoid varied with the developmental stage of the wasp at treatment, and treatment on the egg and last instar caused more adverse effect on the parasitoid than treatment on early and mid instar larvae.