寄主抗药性对菜蛾绒茧蜂生物学特性的影响

以小菜蛾Plutella xylostella敏感品系SP作寄主饲育的菜蛾绒茧蜂Cotesia plutellae SC品系分别寄生于小菜蛾的SP品系(SC-SP组合)或抗性RP品系(SC-RP组合)，还以小菜蛾RP品系作寄主饲育的菜蛾绒茧蜂RC品系分别寄生于小菜蛾的SP品系(RC-SP组合)或RP品系(RC-RP组合)，均在幼虫中期施用氰戊菊酯，考察了药剂对该蜂生物学特性的影响。结果发现：在不施用杀虫剂时，SC-RP组合中蜂的结茧率为45.8%，显著低于其它组合, 所结茧长0.76 mm，育出雌蜂前翅和后足胫节长分别为3.28 mm和2.33 mm，也分别小于其它各组合的结果，表明寄主抗药性对该蜂有不利影响；施用杀虫剂后，RC-RP、SC-RP组合中，蜂的结茧率分别为95.5%和37.8%，显著高于SC-SP和RC-SP组合中蜂的结茧率（22.5%，25.8%），表明寄主抗性能保护其体内的幼蜂少受杀虫剂的影响；RC-SP组合在受到和未受到杀虫剂作用时茧的羽化率分别为95.2%和93.6%，无显著差异，卵+幼虫及雌蛹的发育历期在处理和对照间也无显著差异，表明用抗性寄主饲育的菜蛾绒茧蜂在寄生敏感寄主时仍表现一定的耐药性，有利于该蜂抗药性的发展，即寄主 寄生蜂之间在抗药性方面存在协同进化。

Effects of host insecticide resistance on the biological characteristics of Cotesia plute-llae

The effects of strains of Plutella xylostella (Lepidoptera: Plutellidae), strains of Cotesia plutellae (Hymenoptera: Braconidae), fenvalerate and their interactions on the biological characteristics of C. plutellae were studied in the laboratory. Two strains of P. xylostella, one susceptible to fenvalerate (SP) and the other resistant (RP), and two strains of C. plutellae , one that had been reared using SP as host (SC) and the other which had been reared using RP as host (RC), were arranged in four host parasitoid combinations, i.e., SC SP, SC RP, RC SP, and RC RP. The results showed that, in the absence of the insecticide, the parasitoids in the SC RP combination had a lower percentage of cocoon formation (45 8%), shorter cocoon length (7 8 mm) and females had shorter forewings (3 28 mm) and hind tibia (2 33 mm), compared to those in SC SP, RC SP, and RC RP combinations. This indicated that insecticide resistance in the host had detrimental effects on the parasitoid. When fenvalerate was applied to the host parasitoid system, percentages of cocoon formation in the RC RP and SC RP combinations were 95 5% and 37 8%, respectively, significantly higher than those in the SC SP (22 5%) and RC SP (25 8%) combinations, suggesting that host insecticide resistance offered some protection to the parasitoid larvae inside the hosts. When the RC SP combination was either unexposed or exposed to the insecticide, the parasitoids had similar percentages of adult emergence (93 6% vs 95 2%) as well as similar development times, indicating that the parasitoids, which had been reared on a resistant host strain, still showed some tolerance to the insecticide when parasitizing a susceptible host strain, and this effect should favour the development of insecticide resistance in the parasitoid. This demonstrates co evolution in the development of insecticide resistance in this host parasitoid system.