关键词: 小菜蛾, 杀虫双, 杀螟丹, 抗性

Abstract: 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-resistam and cartap-resistant strains to 11 insecticides were tested. The results showed that the resistant strains had marked positive cross-resistance 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 merry 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 Sv₁ to the fourth instar larvae would increase their sensitivity to the insecticides, thesynergism in dimehypo-resistant strain was 6.28 times for Pb and 1.45 for Svt, and in the cartap-resistant stain 4.85 and 1.39 times, respectively. It seems that MFO is an important factor for the moth to resist dimehyp and cartap.

Key words: Plutella xylostella——dimehypo——cartap——insecticide resistance