Multiple mechanisms responsible for differential susceptibilities ofSitobion avenae(Fabricius) andRhopalosiphum padi(Linnaeus) to pirimicarb

Abstract

AbstractBothSitobion avenae(Fabricius) andRhopalosiphum padi(Linnaeus) are the most important pests of wheat in China and usually coexist on the late period of wheat growth. Pirimicarb was introduced into China for wheat aphid control in early 1990s, and differential susceptibilities ofSitobion avenae(Fabricius) andRhopalosiphum padi(Linnaeus) to pirimicarb have been observed. A bioassay exhibited thatRhopalosiphum padipossessed significantly higher susceptibility to pirimicarb thanSitobion avenae. The addition of synergists DEF, an esterase inhibitor, PBO, a cytochrome P450 monooxygenase inhibitor, and DEM, a glutathioneS-transferase inhibitor, resulted in apparent reductions in the differential susceptibilities, suggesting the involvement of the above three detoxification enzymes in the differential susceptibility to pirimicarb betweenSitobion avenaeandRhopalosiphum padi. A biochemical analysis showed that the activities of carboxylesterases and glutathioneS-transferases were significantly higher inSitobion avenaethan inRhopalosiphum padi, consistent with the results of synergism. Acetylcholinesterase is the target enzyme of pirimicarb and the sensitivity of acetylcholinesterase to pirimicarb was significantly higher inRhopalosiphum padithan inSitobion avenae. The combined results suggest that multiple mechanisms are likely to be responsible for differential susceptibilities to pirimicarb betweenSitobion avenaeandRhopalosiphum padi. The results obtained from this study should be helpful in the rational applications of insecticides.