Study On Resistance Monitoring, Resistance Selection And Resistance Biochemical Mechanism To Diamondback Moth (Plutella Xylostella) Of Indoxacard

Plutella xylostella(L.) is one of the most important crucifers vegetables pests in the world. It has developed resistance to chemical insecticides because of large-scale use chemical insecticides. Through resistance monitoring and resistance selection, study on sublethal effect, cross-resistance and resistance biochemical mechanism to Plutella xylostella of indoxacard is conducted.Four field populations of Plutella xylostella were collected from Luoyuang, Wuxue, Yixhang, and Yueyang. The toxicity of five insecticides to the four populations was done by dipping leaves method. The results showed that four field populations of Diamondback moth produced high level to extremely high level resistance to beta-cypermethrin. The field populations to abamectin was middle to lower level resistant, and the resistance level increased in two years. The resistance level increased in two years from Yueyang and Luoyang. The results also showed that four field populations of Diamondback moth produced high level to middle level resistance to fipronil and susceptible to tebufenozide, while the resistance level decreased in two years.Based on the bioassay results,3rd instar larvae of Plutella xylostella(L.) were treated with indoxacarb at concentrations corresponding to 0.1 mg/L,0.2 mg/L and 0.4 mg/L by dipping leaves methods. Lower feeding amount, pupation rate, eclosion rate and egg hatchability were observed compared with control, adult emergence rate, egg number per female decreased significantly when Plutella xylostella(L.) exposed to indoxacarb.After selection with indoxacarb after 18 generations, a resistant strain was achieved with resistance ratio of 5.14 compared with the relative susceptibe strain. Plutella xylostella (L) had low capability of developing resistance to indoxacarb, as was confirmed by resistance risk assessment. Through Bioassay, analysis and comparison the LC50 values of beta-cypermethrin, abamectin, fipronil and tebufenozide between the resistant strain and susceptible strain, suggesting that indoxacarb-resistant Plutella xylostella(L) had little cross-resistance to these insecticides.The activities of detoxification enzymes were analyzed in both the resistant and susceptible strains. The results showed that the activity of esterase increased by 1.37 fold compared with the susceptible strain, while the activities of mixed function oxidase was 1.36 and glutathione-S-transferase was 1.15, but the difference had no significant.