Enhanced activity of esterases and glutathion-s-transferases in abamectin resistant populations of Panonychus citri (Acari: Tetranychidae)

Citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae) is one of the most important pest of citrus in the citrus regions of the world and Northern provinces of Iran. Application of various chemical pesticides against citrus pests has destroyed natural enemies, the occurrence of resistance and the resurgence of the pests. In this research, resistance mechanisms of citrus red mite to abamectin were investigated in four populations. To determine the LC50, the spray potter tower method was used. In this method, the resistance level in Gorgan, Ramsar, and Sari populations was 6.48, 6.19 and 5.11 times higher than the susceptible population. The measurement of esterase activity in Gorgan's resistant population using α-naphthyl acetate and β-naphthyl acetate substrate was 7.960 and 3.575 times more than that of the susceptible population. Estimation of kinetic parameters and glutathione-s-transferase activity level using 1-chloro-2,4-dinitrobenzene (CDNB) as substrate also showed a significant difference between the four populations, so that the activity of this enzyme in resistance population was 2.79 fold higher than that of resistant population. Also, Km and Vmax in resistant population were 16.12 and 5.33 fold than susceptible population, respectively. Due to the increasing trend of resistance, the results of this study indicated the role of esterase and glutathione-s-transferase enzymes in resistance mechanism to abamectin.