Studies On Monitoring And Mechanism Of Insecticide Resistance In Spodoptera Exigua

Spodoptera exigua is a worldwide distributed polyphagous pest on various cultivated crops, including vegetables, cotton, fruitrees, ornamentals, and so on. In past two decades Spodoptera exigua has emerged as a serious pest in many countries. Resistance to 10 insecticides in five field populations of Spodoptera exigua, was evaluated in laboratory.Reistance to cyhalothrin is the most.Biochemical mechanism of resistance in Spodoptera exigua, to cyhalothrin has been investigated by enzyme synergists (PBO, SVI, DEF and DEM) and enzyme activities assays of esterase, glutathione S-transferase. The synergism ratios of PBO, SV, DEF and DEM to cyhalothrin were 1.2, 1.6, 1.7 and 1.6 folds in susceptible strain, respectively; 47.1, 38.6, 9.1and6.9-fold in resistant strain, respectively. Ratios between resistant and susceptible strain were 39.3, 24.1, 5.4 and 4.3 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 were1.04, 1.10, respectively, no significant difference. All these indicated that detoxification enzymes such as esterase, glutathione S-transferase contributed little to the resistance of spodoptera exigua to cyhalothrin.