菜蛾绒茧蜂和小菜蛾对杀虫剂的敏感性及酶学特性的比较研究

分别采用药膜法和浸叶法测定了菜蛾绒茧蜂Apanteles plutellae和小菜蛾Plutella xylostella对杀虫剂的敏感度。结果显示： 有机磷、氨基甲酸酯、拟除虫菊酯类杀虫剂、阿维菌素和锐劲特对菜蛾绒茧蜂高毒，而抑太保和Bt为低毒，然而，短时间(1 h)接触常规防治剂量的锐劲特、氰戊菊酯、氯氰菊酯和乙酰甲胺磷对菜蛾绒茧蜂低毒。增效剂胡椒基丁醚（PB）、磷酸三苯酯（TPP）和马来酸二乙酯（DEM）对菜蛾绒茧蜂的甲胺磷、克百威、氰戊菊酯、氯氰菊酯、阿维菌素和锐劲特敏感性增效显著，但对抑太保无增效作用。PB的增效作用显著高于TPP 和DEM。PB和TPP对菜蛾绒茧蜂羧酸酯酶(CarE)，以及DEM对谷胱甘肽S转移酶(GST)具显著的活体抑制作用，但PB,TPP和 DEM对菜蛾绒茧蜂乙酰胆碱酯酶（AChE）无抑制作用。菜蛾绒茧蜂AChE的米氏常数(K_m)、最大反应速度(V_max)、CarE和GST活性分别为小菜蛾的0.22、2.08、4.60和0.45倍，甲胺磷、敌敌畏和克百威对菜蛾绒茧蜂AChE的双分子速度常数(Ki)分别为对小菜蛾的14.7、10.5 和26.0倍。酶与抑制剂反应温度增高将导致酶抑制率增高，尤其对菜蛾绒茧蜂AChE的抑制作用更为显著。上述结果表明，菜蛾绒茧蜂对有机磷和氨基甲酸酯类杀虫剂的高敏感性与其显著高的AChE敏感性有关，氧化代谢的解毒作用对菜蛾绒茧蜂耐药性的影响大于水解作用。此外，对小菜蛾和菜蛾绒茧蜂杀虫剂敏感性差异的毒理学原因进行了讨论。

Susceptibility to insecticides and enzymetic characteristics in the parasitoid Apanteles plutellae Kurdj.(Hymenoptera:Braconidae) and its host Plutella xylostella (L.)( Lepidoptera:Yponomeutidae)

The susceptibility to insecticides in the larval pa rasitoid Apanteles plutellae Kurdjumov (Hymenoptera: Braconidae) and its ho s t Plutella xylostella (L.) (Lepidoptera: Yponomeutidae),collected in Fuzho u, China, were detected usi ng residual film and leaf-dip bioassays, respectively. The results showed that o rganophosphates, carbamates, pyrethroids, avermectins and fipronil were highly t oxic to A. plutellae, but chlorfluazuron and Bt were not. However, A. plut ellae could survive from the conventional control doses of fipronil, fenvalera te, cype rmethrin and acephate if the parasitoid was left in contact with the insecticide s only for short time (1 h). In A. plutellae, there were obvious synergisms of pip eronyl butoxide (PB), triphenyl phosphate (TPP) and diethyl maleate (DEM) on me thamidophos, carbofuran, fenvalerate, cypermethrin, avermectins and fipronil, b ut no synergisms on chlorfluazuron were found. The synergism of PB was the highe st. Acetylcholinesterase (AChE) activity could not be inhibited by PB, TPP and D EM, but strong inhibition could be found in carboxylesterase (CarE) activity by PB and TPP, and in glutathione-S-transferase (GST) activity by DEM, in vivo . The apparent Michaelis-Menten constant (K_m), the maximal velocity ( V_(max)) of AChE, and the activities of CarE and GST in A. plutellae w ere 0.22, 2.08, 4.60 and 0.45-fold as those in P. xylostella, respectiv ely. The bimolecular rate constants (K_i) of AChE to methamidophos, dichlor vos and carbofuran in A. plutellae were 14.7, 10.5 and 26.0-fold as thos e in P. xylostella, respectively. High inhibition o f AChE was found in both species when being incubated with insecticides at high temperature, especially in A. plutellae. The results indicated that the high sus ceptibilities to organophosphates and carbametes in A. plutellae were relate d to its high sensitivity of AChE to the insecticides, and the oxidative metabolism might be more effective in tolerance to insecticides than non-oxidative metabol ism in A. plutellae. In addition, the causes of the intrinsic differences i n insecticide selectivity in the two species were also discussed.