Assessment Of Resistance Risk And Resistance Machanism In Spodoptera Exigua(H(u|¨)bner) To Chlorantraniliprole

In this paper, chlorantraniliprole resistance was selected in S. exigua, the resistance risk was estimated. The resistance to other insecticides of this strain, the change of detoxification enzymes activities after selection and the influence of chlorantraniliprole sublethal dose to detoxification enzymes activities in S. exigua were studied.1. Assessment of resistance risk in S. exigua to chlorantraniliproleBased on22generations of chlorantraniliprole selection in S. exigua, writer was in charge of selection from23to48generation, and the LC50raised from1.8821mg/L to6.3807mg/L with3.4-fold increase.Compared with the susceptible strain, the resistance ratio had reached465.7-fold.The realized heritability (h2) of resistance was estimated as0.0597by using threshold trait analysis, when the slope is2.30, h2is0.0597,70%-90%of the population is killed at each generation,10-fold increase in LC50need21.9-31.1generations, indicating that the risk of resistance development exists in S. exigua to chlorantraniliprole after continuous application.2. The resistance to conventional insecticides of selected strainUsing leaf dipping bioassay to determine12conventional insecticides resistance of selected strain, the results showed that the resistance to chlorpyrifos (RR>12526.8), cyhalothrin (RR>864), chlorfluazuron (RR=679.2), metaflumizone (RR=535.9), indoxacarb (R-R=151.7), pyridalyl (RR=47.7) were very high, the resistance to spinosad and methomyl belong to moderate resitance with resistance ratio of23.7and11, and the resistance to endosulfan, flubendiamide, emamectin enzoate were low with RR of9.9,7.7,1.9respectively. As the original population of selected strain was collected on Brassica rapa chinensis in Shanghai in2008, low and moderate resistance maybe caused by different genetic and environmental background with susceptible strain, high level resistance to7conventional insecticides was related to original population’s resistance developed during the long-term application of some commonly used insecticides before2008, which is also maybe the reason of some novel pesticides’s resistance, such as metaflumizone and Pyridalyl. All the resistance above didn’t reverse during the selection, so they don’t suggest to be used mixing with chlorantraniliprole.In order to investigate the resistance biochemical mechanism, PBO, DEF, DEM and methimazole were used with five insecticides. DEF significately synergized chlorantraniliprole with synergism ratios (SR) of2.3, means the esterase involved in the detoxification mechanism to chlorantraniliprole in S.exigua. DEF, DEM, methimazole showed2.6-,2.7-,2.2-fold SR on metaflumizone respectively, indicating that esterase, glutathione-S-transferase enzymes and FMO may involve in the detoxification of S. exigua to metaflumizone.Pretreating with PBO, the toxicity of cyhalothrin was significately synergized with SR of3.6, means P450plays an important role in the high resistance to pyrethroid in S. exigua. Methimazole obviously synergized emamectin benzoate (SR=2.7), maybe because compared with the concentration of synergist, emamectin benzoate’s LC50was low, which can provide guidance for synergist concentration selection in the future.3. The influence of chlorantraniliprole’s sublethal dose to detoxification enzymse in the body of the beet armywormThe weight of larvae which exposed to chlorantraniliprole’s LC15maitained around2mg, and the development delayed obviously, while larvae weight of control group increased signicantely. All the detoxification enzymes activities in the control group almost didn’t change at first, and went up later. P450had a significant rise after16h, FMO raised after24h, esterase significantly increased after72h, GST increased after36h. But all the detoxification enzymes activities in the treated group were almost unchanged during the96h, indicating that they all can’t be induced by chlorantraniliprole. But esterase involved in detoxification to chlorantraniliprole in the selected strain, maybe because the selective pressure killed larvaes whose detoxification enzymes activities were low.