Biochemical basis of insecticide resistance and determination of esterase enzyme patterns in field collected populations of Cotesia vestalis (Haliday) (Hymenoptera: Braconidae) from India.

Abstract

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 thethree 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 esteraseactivity was observed in the resistant populations of the parasitoid collected from Hyderabad, Pune, Tirupathi andVaranasi. The enzyme activity was more pronounced with respect to Novoluron 10% EC (0.15-0.34IU/mg/protein/min) than Indoxacarb14.5% SC (0.13-0.31 IU/mg/protein/min) and Spinosad 45% SC (0.03-0.32IU/mg/protein/min). Native PAGE and α-naphthyl acetate staining, revealed carboxylesterase bands in the variouspopulations of the parasitoid. Variations in populations and degree of resistance accounted for the detoxifyingenzyme activity. The use of potentially resistant parasitoids in biological control programmes is discussed.