Studies on dissipation kinetics and risk assessment of imidacloprid residues and bioefficacy of some insecticides against Hemipteran pest in okra
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Date
2018-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
In the present study field investigations were carried out at Vegetable Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar during spring and rainy season of 2017, respectively. Three species of hemipteran insect pest viz., leafhopper (Amrasca biguttula biguttula Ishida), Whitefly (Bamisia tabaci Genn.), Aphid (Aphis gossypii Glover) were observed to attack the okra crop during both spring and rainy season 2017. Among all the insecticidal treatment, imidacloprid 17.8 SL @ 100ml/ha followed by acetamiprid 20 SP @ 75 gm/ha was found to be highly effective against aphid and leafhopper population and thiamethoxam 25% WG @ 100 gm/ha was found most effective to suppress whitefly population. Yield was recorded maximum in acetamiprid 20 SP@ 75gm/ha treated plots. Yield of okra in rainy season (15.17/ha) was more than spring season (13.04 T/ha). Seasonal incidence of all the pest under study was observed from 13th standard meteorological week to 25th standard meteorological week of 2017. Maximum mean population of leafhopper (16.10 leafhopper/3 leaves) and whitefly (15.31 whiteflies/3 leaves) was recorded during 21st SMW of 2017.And peak population of aphid (31.52 aphids/3 leaves) was observed during 21st SMW of 2017 in spring season. During rainy season of 2017, seasonal incidence of all the pest species under study was studied from 32nd standard meteorological week to 43rd standard meteorological week of 2017. Maximum mean populations of leafhopper (12.12 leafhopper/3 leaves), whitefly (12.85 whiteflies/3 leaves) and aphid (20.98 aphids/3 leaves) were recorded during 40th SMW of 2017. Residue of imidacloprid was dissipated to more than 80 % after 3 days of spraying and it was found to be below detectable limit at 7 and 10 days. Half life period for imidacloprid at tarai region of north western Himalaya was estimated to be 2.094 days at recommended dose. As the RQ (Risk Quotient) value was found to be less than 1 after 3 day (0.85).Hence, 3 days waiting period have been suggested for imidacloprid in okra crop in agroclimatic region of tarai during rainy season.
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