STUDIES ON INSECTICIDE USAGE PATTERN AND DEVELOPMENT OF RESISTANCE IN DIAMONDBACK MOTH, PLUTELLA XYLOSTELLA LINNAEUS (LEPIDOPTERA: PLUTELLIDAE)
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Date
2019-08
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bengaluru).
Abstract
The study was conducted to know the insecticide usage pattern in major cole crops growing areas of Karnataka to develop baseline data for selected insecticides and variations in development of resistance in Diamondback moth (DBM) populations of different regions to selected insecticides and biochemical mechanisms involved in insecticide resistance. It was found that totally 24 insecticides were used by the farmers for the management of insect pests of cole crops. Dichlorvos 76 EC was found that most used insecticide (16.55%). Among the surveyed districts, maximum numbers of insecticides were used in Kolar (15) and least in Mysuru (6). The susceptible DBM population was used to establish baseline susceptibility data for selected insecticides. The LC50 value representing toxicity, varied across insecticides, emamectin benzoate 5 SG showed highest toxicity and dichlorvos 76 EC showed least toxicity. The mean resistance ratio observed to be varied across locations and across insecticides. The mean resistance ratio was highest for Kolar (2.54 fold) and least observed for Belagavi (1.99 fold). Among insecticides it was higher for chlorantraniliprole 18.SC (3.94 fold) and least for spinosad 45 SC (1.30 fold). The biochemical mechanisms involved in insecticide resistance was revealed by esterase enzyme activity, it varied across DBM population of different districts and also across insecticides. It was very low in untreated susceptible population (19.80 mol./min/g) compared to treated susceptible (24.89 mol./min/g), untreated field (34.71 mol./min/g) and treated field (39.91 mol./min/g) populations. The enzyme activity was positively correlated with the resistance ratio for all the insecticides studied in DBM populations. Overall study indicated that insecticide usage pattern influences development of resistance in DBM and is revealed by biochemical mechanisms of insecticide resistance.