Studies On Monitoring And Echanism Of Insecticide Resistance In Tetranychus Urticae Koch

Tetranychus urticae Koch is a worldwide distributed polyphagous pest on various cultivated crops, including vegetables, cotton, fruitrees, ornamentals, and so on. In past two decades Tetranychus urticae Koch has emerged as a serious pest in many countries. Resistance to 8 insecticides in five field populations of Tetranychus urticae Koch, was evaluated in laboratory.Reistance to bifenthrin is the most.Biochemical mechanism of resistance in Tetranychus urticae Koch, to bifenthrin has been investigated by enzyme synergists (PBO, SVI, DEF and DEM) and enzyme activities assays of esterase, glutathione S-transferase and microsomal O-demethylase. The synergism ratios of PBO, SV,, DEF and DEM to cyhalothrin were 2.41,1.53, 1.16 and 1.79 folds in susceptible strain, respectively;38.97, 32.02, 4.61and 5.16-fold in resistant strain, respectively. Ratios between resistant and susceptible strain were 16.17, 20.93, 3.97 and 2.88 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 bifenthrin. Synergism to bifenthrin by DEF and DEM was not much significant. The ratios of enzymatic activity of esterase, glutathione S-transferase and microsomal O-demethylase in susceptible and resistant strains were 1.01, 1.14 and 1.05 respectively, no significant difference. All these indicated that detoxification enzymes such as esterase, glutathione S-transferase and microsomal O-demethylase contributed little to the resistance of beet armyworm to bifenthrin.