FIELD BIOEFFICACY AND RESIDUE DYNAMICS OF THIACLOPRID AND EMAMECTIN BENZOATE IN CHILLI AGAINST THRIPS, Scirtothrips dorsalis Hood
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Date
2022
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DRPCAU, PUSA
Abstract
“Field Bioefficacy and Residue Dynamics of Thiacloprid and Emamectin Benzoate in Chilli against Thrips, Scirtothrips dorsalis Hood” was carried out at “Dr. Rajendra Prasad Central Agricultural University, Pusa” during the summer season of 2022. Thiacloprid 21.7% SC and Emamectin benzoate 5% SG was sprayed three times on the chilli crop at their recommended dose, 1.5 times the recommended dose and twice the recommended dose for bioefficacy study. Emamectin benzoate at its double dose reduced the thrips population to 1.20 / 3 leaves / plant after 10 days from the 3rd spray, with the highest overall mean reduction over control (86.63 %). Highest green chilli yield of 76.30 q/ha was obtained from this treatment with an 18.72 % increase in yield over control and ICBR of 1:3.86. For residue study insecticides were sprayed at recommended and double the recommended dose. Representative chilli samples were analysed by UHPLC following slightly modified QuEChERS technique. After second and third application, initial residue deposit for thiacloprid at recommended and twice the recommended dose varied from 0.67-0.69 mg/kg and 1.14-1.19 mg/kg, respectively. Initial emamectin benzoate residues at 0 day for recommended and double dose ranged from 0.29-0.30 mg/kg and 0.42-0.48 mg/kg, respectively. Thiacloprid residue dissipated below the LOQ level after 7 and 10 days
for recommended and double dose, respectively. Residue of emamectin benzoate at recommended and double dose reached below LOQ level after 5 days. After assessment of dissipation pattern of thiacloprid, its half-life value in chilli was found to be 2.01-1.94 days at recommended dose and 1.96-2.30 days at double dose. Initial residue amount from recommended dose decreased to reach below the prescribed MRL value after 8.79-8.75 days. Similarly, initial deposit from the double dose reduced below MRL value after 10.22-11.96 days. Residue of emamectin benzoate at recommended and double dose reached half-life value at 0.76-0.88 days and 1.25 days, respectively. The residue level of emamectin benzoate at recommended and double dose was calculated to reach below the prescribed MRL value after 2.08-2.42 days and 3.85-4.02 days, respectively. Thus, a safe waiting period of 9 days is suggested for thiacloprid in chilli at recommended dose. Similarly, a safe waiting period of 3 days is found suitable for emamectin benzoate when sprayed at its recommended dose. Among the three doses of thiacloprid, its application at 72 g a.i./ha effectively decreased thrips population, with good ICBR and had an acceptable waiting period. Similarly, emamectin benzoate at 10 g a.i. per ha was found to effectively manage thrips population, besides having a high ICBR value, safe waiting period and posing less residue load on the environment. Between both the insecticides, the recommended dose of emamectin benzoate is more effective in managing thrips population along with high returns, high ICBR and low waiting period for safe consumption of chilli by following GAP.