Insecticide resistance in Cotesia vestalis, a braconid endolarval parasitoid of the Diamondback moth Plutella xylostella. Resistance was assessed in the parasitoid populations collected from Anand (Gujarat), Bangalore (Karnataka), Bhubaneshwar (Odisha), Coimbatore (Tamilnadu), Delhi , Hyderabad (Andhra Pradesh), Pune (Maharshtra), Jorhat (Assam), Tirupathi (Andhra Pradesh) and Varanasi (Uttar Pradesh). Three insecticides viz., Spinosad 45% SC, Indoxacarb 14.5% SC and Novoluron 10% EC were evaluated for resistance through qualitative and quantitative bioassays. The parasitoid population from Hyderabad was more resistant to all the three insecticides than others, based on the LC50 values with a resistant factor of 79.76, 12.92 and 17.28, respectively, while the population from Delhi was susceptible to all the insecticides. Enhanced carboxyl esterase activity was observed in the resistant populations of the parasitoid collected from Hyderabad, Pune, Tirupathi and Varanasi. The enzyme activity was more pronounced with respect to Novoluron 10% EC (0.15-0.34 IU/mg/protein/min) than Indoxacarb14.5% SC (0.13-0.31 IU/mg/protein/min) and Spinosad 45% SC (0.03-0.32 IU/mg/protein/min). Native PAGE and α-naphthyl acetate staining, revealed carboxylesterase bands in the various populations of the parasitoid. Variations in populations and degree of resistance accounted for the detoxifying enzyme activity. The use of potentially resistant parasitoids in biological control programmes is discussed
