Study On Indoxacarb Resistance In Diamondback Moth, Plutella Xylostella

Diamondback moth, Plutella xylostella (L.), has become a worldwide important pest of cruciferous vegetables, it has seriously affected the cultivation of cabbage, broccoli and other cruciferous vegetables. Chemical control is still a dominant measure to control diamondback moth. Due to the frequent use of all kinds of insecticides, P. xylostella has developed different degrees of resistance, it leds great difficulties to control them. In order to control diamondback moth effectively, we did some research on montoring resistance of field populations to indoxacarb in central China, screening the optimum ratios on the mixtures of indoxacarb and other insecticides, resistance selection by indoxacarb, resistance biochemical mechanism and the synergism of the synergists to indoxacarb.1Rsisitance monitoring of P. xylostella to indoxacarb in central ChinaFive field populations (Luoyang, Yichang, Yunmeng, Wuxue, Yueyang) of P. xylostella were collected from cabbage fields in central China from2012to2013to monitor their resistance to indoxacarb by using a leaf-dipping bioassay method. Results indicated that resistance ranged from low to moderate level in this area, the resistance level was relatively higher in the field population of Luoyang and Yueyang, with the resistance ratio from19.42to26.6fold, low to moderate resistant level was occurred in Wuxue and Yichang population, with resistance ratio was8.76to20.4fold, the resistance was the minimum in Yunmeng among the populations, with the resistance ratio from7.1to12.33fold.2Co-toxicity of indoxacarb with other three insecticides against P. xylostellaThe co-toxicity of indoxacarb with three insecticides was tested by leaf-dipping bioassay method. The results showed that indoxacarb mixed with spinosad or chlorfenapyr had no synergistic effect, indoxacarb with diafenthiuron of0.33:7.84,0.28:9.81,0.11:15.69had remarkable synergistic effect, with the co-toxicity coffiecient were174.32126.01、133.64respectively. 3Resistance selection of P. xylostella by indoxacarb and synergistic effectTo undersand the development of generated resistance, the resistance selection of P. xylostella to indoxacarb was carried out in laboratory. After24generations of continuous selection pressure, resistance to indoxacarb was12.77-folds in thisstrain compared with the unselected parents, the resistance ratio rose faster during F0to F4, but it changed a little during F4to F10, after F14it rose faster. The addition of diethyl maleate (DEM) had almost no effect on the toxicity of indoxacarb to F17generation while piperonyl butoxide (PBO) could increase the toxicity of indxacarb to it, with the synergism ratio were1.02and3.78respectively.4Resistance biochemical mechanism to indoxacarb of P. xylostellaThe effect on activities of detoxification enzymes in indoxacarb-selected P. xylostella were investigated. Results indicated that the activities of glutathione S-transferases (GST) and mixed-function oxidase (MFO) in P. xylostella larvae of F23generation increased1.63and1.46fold respectively, whereas the activities of carboxylesterase (CarE) was distinctly inhibited, it is0.65fold compared with the unselected strain.