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

Five field populations of Plutella xylostella were collected from Hainan, Sandong, Wuhan, Guangdong and Xiangfan, respectively. The toxicity of nine insecticides to the five populations was done by dipping leaves method. The results showed that five field populations of Diamondback moth produced middle level resistance to cypermethrin with 36.69, 34.97, 11.46, 20.34 and 22.75-fold respectively. The field population from Sandong to abamectin was highly resistant with 135.06-fold resistance, and sensitive to other seven insecticides including fipronil, spinosad, flufenoxuron, phoxim, chlorfluazuron, chlorfenapyr and dimehypo. The field population from Guangdong produced middle level resistance to abamectin, chlorfluazuron, flufenoxuron , with 30.47, 10.21 and 19.85-fold resistance, and sensitive or low resistant to other five insecticides including fipronil, spinosad, phoxim, chlorfenapyr and dimehypo. Whereas the field populations from Hainan, Wuhan, Xiangfan were sensitive or low resistant to other eight insecticides except of cypermethrin, respectively. Selection of a susceptible strain of diamondback moth {Plutella xylostella) with fipronil and spinosad resulted in a moderate level resistance. After 20 generation, the resistance ratios of diamondback moth to fipronil and spinosad were 12.31 and 14.47 compared with that of the unselected parental strain respectively. Between the strain unselected and the strain selected by fipronil the activity of glutathione S-transferases(GSTs) was highly remarkable different, whereas the activities of acetylcholinesterase(AchE), carboxylesterase(CarE) and polyphenol oxidase(PPO) were not remarkable different. The result indicated that glutathione S-transferases(GSTs) might be involved in resistance mechanism of Diamondback moth to fipronil. Between the strain unselected and the strain selected by spinosad the activities of glutathione S-transferases(GSTs) and acetylcholinesterase(AchE) were highly remarkable different, whereas the activities of carboxylesterase(CarE) and polyphenol oxidase(PPO) were not remarkable different. Thisindicated that glutathione S-transferases(GSTs) and acetylcholinesterase(AchE) might be involved in resistance mechanism of Diamondback moth to spinosad.