Monitoring Insecticide Resistance And Studies On Resistance Mechanisms Of Chlorantraniliprole In Spodoptera Exigua

The beet armyworm, Spodoptera exigua(L.), is a worldwide distributed and polyphagous pest which has developed resistance to many insecticides, including Chlorantraniliprole. In this paper, beet armyworm populations from four areas were resistance monitored. The biological assay and resistant mechanism of Spodoptera exigua to chlorantraniliprole were also tested in this study. In addition, research on the expression quantities of GSTs1mRNA in Spodoptera exigua larvae was studied by quantitative RT-PCR method.1、 In this study,susceptibility to several classes of insecticides was determind using leaf-dipping method in field populations of Spodoptera exigua from4areas of Hunan and Guangxi Provinces, in China. The results showed that the beet armyworm collected from4filed populations developed high levels of resistance to beta-cypermethrin. Morderate levels to monosultap and chlorpyrifos. Low and morderate levels to methoxyfenozide, chlorantraniliprole, Chlorfenapyr, fipronil, avermectin. Low levels to emamectin benzoate and endosulfan.2、Three enzyme synergists were tested to find out the synergism to chlorantraniliprole. The results showed that the synergism ratios of DEM to chlorantraniliprole in the susceptible and Changsha strain was not much significant which was1.33and1.72folds respectively. But it showed a significant synergism in Yueyang strain with3.42folds high. Meanwhile the study on activities of three metabolism enzyme were compared among the susceptible and resistant strains. The result indicated that the enzyme activities of carboxylesterase was the highest in the fifth larvae of the resistant strains. The enzyme activities of cytochrome GST was the highest and lowest respectively in the third (3.64folds) and the first to second larvae(1.73folds) of the Yueyang strain. And it was in the third (2.53folds) and first to second (1.64folds) larvae of the Changsha strain.The activities of P450was the highest in third larvae(1.197folds) and lowest in the fifth larvae(1.131folds) of the Yueyang strain. And it was in the forth (1.138folds) and fifth (1.052folds) larvae of the Changsha strain.3、The expression quantities of GSTsl mRNA in Spodoptera exigua larvae in different stages, as well as different tissues and parts of the third larvae were studied by quantitative RT-PCR method. The results showed that the highest expression level was in the third larvae with a7.4-fold higher than that in the fifth larvae; moreover, the expression level in fat body was relatively higher than that in integument, mid-gut and malpighian tubule, and the expression level in thorax was also higher than that in head and abdomen.The expression level of GSTs1gene in the third larve treated with chlorantraniliprole was2.31-fold comparing with that of the susceptible strain.