Field-evolved insecticide resistance and biochemical validation of enzyme activities in diamondback moth, Plutella xylostella

In the study against diamondback moth (DBM), 11 field populations were collected from cabbage during 2012 and 2013 to monitor the level of resistance to organophosphorus compounds (acephate and chlorpyriphos), synthetic pyrethroid (cypermethrin), oxadiazine (indoxacarb), naturalyte (spinosad) and diflubenzoylureas (novoluron) by using leaf dip bioassay method. DBM showed moderate to high resistance to chlorpyriphos, cypermethrin and acephate where the Oddanchatram (PX-3) population being the most resistant (275.61-fold, 108-fold and 52.07-fold for chlorpyriphos, cypermethrin and acephate, respectively). Biochemical validation of enzyme activity was also investigated by quantifying carboxylesterase, glutathione S transferase (GST) and cytochrome P-450. Metabolic inhibitors viz., S, S, S-tributylphosphorotrithioate (DEF), piperonylbutoxide (PBO) and diethyl malate (DEM) clearly proved the role of carboxylesterase and cytochrome P-450 in conferring high level of resistance to Oddanchatram population (PX-3) for chlorpyriphos, cypermethrin and acephate.