INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT Biochemical Basis of Organophosphate and Carbamate Resistance in Asian Citrus Psyllid

TheAsiancitruspsyllid,Diaphorina citriKuwayama, is aworldwidepest of citrus,which vectors the putative causal pathogen of huanglongbing. Current management practices warrant continuous monitoring of Þeld populations for insecticide resistance. Baseline activities of acetylcholinesterase (AChE), general esterase, and glutathione S-transferase as well as sensitivity of AChE to selected organophosphate and carbamate insecticides were established for a susceptible laboratory strain (Lab) and comparedwith several Þeld populations ofD. citri from Florida. The speciÞc activity of AChE in various D. citri populations ranged from 0.77 to 1.29 Mmin 1 mg of protein ; the Lab strain was characterized by the highest activity. Although reduced AChE sensitivity was observed in the Lab strain compared with Þeld populations, overlap of 95% conÞdence intervals of I50 values (concentration required for 50%AChE activity inhibition) suggests no signiÞcant difference in AChE sensitivity among all populations tested for a given insecticide. There was no signiÞcant evidence of target site insensitivity in Þeld populations that were exposed to the selected organophosphate and carbamate insecticides tested. The speciÞc activity of general esterase and glutathione S-transferase was lowest in the Lab strain and was generally comparable to that of the Þeld populations evaluated. The current data provide a mode-of-action speciÞc baseline for future monitoring of resistance to organophosphate and carbamate insecticides in populations of D. citri.