杀虫双和杀螟丹选育对小菜蛾抗药性的形成及其抗性机制

用杀虫双和杀螟丹在实验室以点滴法处理小菜蛾Plutella xylostella L.四龄幼虫，以连续继代药剂淘汰选育其抗药性。至35代，药剂汰选的小菜蛾对杀虫双和杀螟丹的抗药性较选育前正常品系分别提高了51倍和25倍。其抗药性的形成发展均呈S形，可认为已成为抗性品系。以有机磷、氨基甲酸酯、拟除虫菊酯及有机氮等11种杀虫剂测试抗杀虫双小菜蛾品系和抗杀螟丹小菜蛾品系对常用药剂的敏感度结果表明：对杀虫双、杀螟丹和杀虫环之间有较严重的正交互抗性；对敌敌艮、马拉硫磷和杀螟松有轻微交互抗性产生；对溴氰菊酯、氯氰菊酯、氯菊酯和灭多威、久效威等药剂更加敏感，呈负交互抗性。用聚丙烯酰胺凝胶电泳(PAGE)法测定表明，抗药性产生与特异性酯酶的形成有一定关系。用比色法和酸度法测定，抗性品系的乙酰胆碱酯酶(AchE)活性降低，羧酸酯酶(CarE)活性无差异。加增效剂Pb和SV₁：于四龄幼虫表皮，对抗杀虫双小菜蛾晶系分别有6.28及1.45倍的增效作用；对抗杀螟丹小菜蛾品系分别有4.85及1.39倍的增效作用，可见多功能氧化酶(MFO)为小菜蛾抗杀虫双和抗杀螟丹的重要因子。

DEVELOPMENT OF DIAMOND-BACK MOTH STRAINS RESISTANT TO DIMEHYPO AND CARTAP WITH REFERENCE TO THE MECHANISM OF RESISTANCE

Diamond-back moth (Plutella xylostella) larvae in fourth instar were topically applied with dimehypo and cartap in successive generations in the laboratory to develop resistant strains of the moth. After 35 generations, the resistance of the moth to dimehypo and cartap increased by 51 and 25 folds, respectively. The time course of resistance development appeared to be in S shape.The sensitivities of the dimehypo-resistant and cartap-resistant strains to 11 insecticides were tested. The results showed that the resistant strains had marked positive cross-resista'nce to dimehypo, cartap and thiocydam and slight positive cross-resistance to DDVP, malathion and feni-trothion, but showed negative cross-resistance to deltamethrin, cypermethrin, permethrin, me-thomyl and thiofonox. PAGE demonstrated that the resistance to insecticides was related to the activity of special types of esterase. Activities of CarE and AchE were measured by colori-metry and acidity analysis. The results indicated that in the resistant strains the AchE activity decreased, but he CarE showed on difference in activity. Topical application of the synergist Pb or Svi to the fourth instar larvae would increase their sensitivity to the insecticides, the synergism in dimehypo-resistant strain was 6.28 times for Pb and 1.45 for Svi, and in the cartap-resistant srain 4.85 and 1.39 times, respectively. It seems that MFO is an important factor for the moth to resist dimehyp and cartap.