Studies On Monitoring Insecticide Resistance And Resistance Mechanism To Isoprocarb Of Nilaparvata Lugens St(?)l

Nilaparvata lugens St(a|¨)l is a worldwide distributed polyphagous pest on rice.Resistance to 6 insecticides in six field populations of Nilaparvata lugensSt(a|¨)l, was evaluated in laboratory.Biochemical mechanism of resistance in Nilaparvata lugens St(a|¨)l toIsoprocarb has been investigated by enzyme synergists (PBO, SVI, DEF andDEM) and enzyme activities assays of esterase,ghtathione S-transferaseand microsomal O-demethylase. The synergism ratios of PBO, SV,, DEF andDEM to Isoprocarb were 1.5, 2.8, 1.9, 2.1folds in susceptible strain,respectively; 54.9, 16.5, 11.2, 4.9-fold in resistant strain,respectively. Ratios between resistant and susceptible strain were 36.6,5.9, 5.9, 2.2 folds, respectively. The result shows that synergism tofenvalerate by PBO was the most distinct. This implied that mixed-functionoxidase was involved in the resistance to Isoprocarb. Synergism toIsoprocarb by DEF and DEM was not much significant. The ratios ofenzymatic activity of esterase, ghtathione-S-transferase and microsomalO-demethylase in susceptible and resistant strains were 1.11,1.01, 1.13-fold, respectively, no significant difference. All theseindicated that detoxification enzymes such as esterase, glutathioneS-transferase and microsomal O-demethylase contributed little to theresistance of beet armyworm to Isoprocarb.