氰戊菊酯残留对菜蛾绒茧蜂成虫的致死和亚致死效应

室内测定了氰戊菊酯残留对菜蛾绒茧蜂成虫的致死和亚致死效应。结果发现,氰戊菊酯对菜蛾绒茧蜂成虫的毒力比对小菜蛾2龄幼虫的高10倍以上,因此可以肯定田间施用氰戊菊酯后,可以直接(喷雾)或间接(残留)杀死部分菜蛾绒茧蜂成虫。小菜蛾2龄幼虫LC_(50)剂量的氰戊菊酯残留显著降低了雌蜂的产卵量和供试小菜蛾幼虫的被寄生率,在氰戊菊酯残留存在的情况下,雌蜂的死亡率高于雄蜂,蜂子代存活率及性比显著低于对照。氰戊菊酯残留对菜蛾绒茧蜂的搜索行为也有显著的影响,雌蜂在叶片上停留的时间及用于搜索的时间均高于对照,表明残留对菜蛾绒茧蜂雌蜂的搜寻有刺激作用,但产卵寄生的发生次数与对照间无显著差异。文中对产生上述结果的原因进行了讨论。

Lethal and sublethal effects of fenvalerate residue on adults of Cotesia plutellae

Lethal and sublethal effects of fenvalerate residue on adult wasps of Cotesia plutellae, a larval parasitoid of the diamondback moth, Plutella xylostella, were measured in the laboratory. The toxicity of fevalerate to adults of C. plutellae was more than 10 times higher than that to the second instar larvae of P. xylostella, indicating that, when fenvalerate is applied in the field, a proportion of the parasitoid adults can be killed directly by the spray or indirectly by contact with the residue. When the wasps were exposed to fenvalerate residue at a dose of LC50 to the second instar larvae of P. xylostella, the number of eggs laid per female and the proportion of host larvae parasitized were significantly reduced. In the presence of fenvalerate residue, mortality of female wasps was higher than that of males, and the survival rate and female sex ratio of the parasitoid offspring were significantly reduced compared to those in the control. In addition, the foraging behavior of female wasps was significantly changed by fenvalerate residue. In the presence of fenvalerate residue, female wasps spent more time on the plant leaves and also more time searching around than those in the control, indicating some stimulating effect from the residue on searching by the female wasps. However, the number of ovipositions by female wasps in the presence of fenvalerate residue did not differ significantly from that in the control. Mechanisms for the above results are discussed.