Studies On Monitoring And Mechanism Of Cyfluthrin Resistance In Pieris Rapae

Pieris rapae is a worldwide distributed polyphagous pest on various cultivated crops, including vegetables, cotton, fruittrees, ornamentals, and so on. In past two decades Pieris rapae has emerged as a serious pest in many countries. Resistance to 10 insecticides in five field populations of Pieris rapae, was evaluated in laboratory.Reistance to cyhalothrin is the most.Biochemical mechanism of resistance in Pieris rapae, to cyhalothrin has been investigated by enzyme synergists (PBO, SV1, DEF and DEM) and enzyme activities assays of esterase, glutathione S-transferase and microsomal O-demethylase. The synergism ratios of PBO, SV1,, DEF and DEM to cyhalothrin were 1.3, 1.6, 1.1 and 1.5 folds in susceptible strain, respectively; 47.0, 29.0, 7.1and 5.9-fold in resistant strain, respectively. Ratios between resistant and susceptible strain were 36.2, 18.1, 6.5 and 4.0 folds, respectively. The result shows that synergism to cyhalothrin by PBO was the most distinct. This implied that mixed-function oxidase was involved in the resistance to cyhalothrin. Synergism to cyhalothrin by DEF and DEM was not much significant. The ratios of enzymatic activity of esterase, glutathione S-transferase in susceptible and resistant strains were 1.08, 1.14, respectively, no significant difference. All these indicated that detoxification enzymes such as esterase, glutathione S-transferase contributed little to the resistance of pieris rapae to cyhalothrin.