Monitoring Of Insecticide Resistance And Baseline Susceptibility Of Chilo Suppressalis (Lepidoptera:Pyralidae) To Chlorantraniliprole

The striped stem borer, Chilo suppressails Walker (Lepidoptera:Pyralidae), is an important pest of rice in all rice-growing areas of China, especially in the southeastern provinces around the Yangtze River. Control of this insect in China relies mainly on chemical insecticide, however, the development of insecticide resistance by insect seriously impacted the efficient control in practice.In this study, the resistance of this pest collected from11regions in China to4insecticides were assayed in2010-2011, the bioassay on each population of C.suppressalis was performed by topical application. The results indicated that the resistance levels of the12populations to4insecticides were significantly different among geographic populations. Field populations from Cangnan, Ri’an, Jinhua and Xiangshan in Zhejiang province, Taihe in Jiangxi province, Wuxue and Xiaogan in Hubei province, Lujiang in Anhui province were found to have highly or extremely highly resistant level to triazophos, the resistance ratio was ranging from42.5to302.5fold. However, those populations collected from Yizheng, Hanjiang in Jiangsu province and Dazhou in Sichuan province remained susceptible (RR=1.3-3.9) to this insecticide, the most sensitive population was that from Yizheng in Jiangsu province. High level of resistance to chlopyrifos was observed in the field population collected from Xiangshan in Zhejiang (RR=64.5) province and Lujiang (RR=78.4) in Anhui province. The populations from Cangnan, Ri’an, Jinhua in Zhejiang, Taihe in Jiangxi, Xiaogan in Hubei, Youxian in Hunan and Hanjiang in Jiangsu were of medorate resistance to the compound, whereas other field populations from Wuxue in Hubei, Dazhou in Sichuan and Yizheng in Jiangsu were susceptible or of lower resistant to chlopyrifos (RR<10). The resistance level of the tested12field populations to monosultap was not very high with resistance ratio between1.1and16.2, field populations from Dazhou in Sichuan provinces, Yizheng and Hanjiang in Jiangsu province and Lujiang in Anhui province had became susceptible to monosultap (RR=1.1-2.1), among which Hanjiang population was the most susceptible, and the other populations were of low to moderate resistance to monosultap with the resistance ratio between7.1and16.2. The assay results revealed that rice stem borer in most locations sustained the susceptibility to abamection, among which only four strains from Taihe in Jiangxi, Cangnan and Jinhua in Zhengjiang and Lujiang in Anhui showed low level of resistance to this chemical with resistance ratio between5.6-7.5. The other eight populations maintained susceptibility or only had lower resistance to abamectin (RR<5), among which Dazhou population in Sichuan province was the most susceptible to this insecticide. In conclusion, among the12different geographic populations reported in this dissertation only Cangnan, Lujiang, Ri’an and Taihe strains had developed higher resistance to the tested four insecticides, on the contrary, Dazhou and Yizheng stains were relatively susceptible to the assayed chemicals. And the susceptibility of this insect pest decreased from the north and west part to south and east part of China.In order to implement the integrated resistance management (IRM) of C.suppressalis to chlorantraniliprole in China, the baseline toxicity of this new insecticide to rice stem borer was established, the toxicity responses of stem borer from22different geographic regions to chlorantraniliprole were assayed by rice seedling dipping method. The assay data showed that C.suppressalis populations from different areas displayed wide variation in susceptibilities to chlorantraniliprole, The LC50values varied from0.821mg ai/L for the most susceptible population (Fushun, in2011) to16.704mg ai/L for the least susceptible one (Wuxue, in2011). There were significant difference in susceptibilities among the22tested populations, nonetheless, geographic distribution pattern of insecticidal susceptibility could not deduced from these toxicity data of this insect species. No difference in susceptibility in field populations between2010and2011were found with only one exception that the LC50of Lujiang population in Anhui province was lower in2011than in2010. According to the two year’s data from different geographic locations, the pooled toxicity response of rice stem borer to chlorantraniliprole were calculated, the baseline response was established, Y=1.014X-0.654could be considered as the susceptibility baseline.In the same time of bioassay, the metabolic enzyme activities were also measured for these field populations. Significant difference in activities of esterase, p450mono-oxygenases and glutathione S-transferases existed in the field-collected populations. However no correlation between the levels of insecticide resistance and enzyme activities were found in our research.