Residues of Spirotetramat and its metabolite in Tea and Soil

Abstract

Spirotetramat is a systemic, ambimobile, keto-enol group of insecticide developed by Bayer Crop Science against sucking insects, eg. aphids, mites, thrips and white flies. To generate data on residues in tea and soil after application of Movento (Spirotetramat 150 OD) supervised field trials were carried out at 4 locations viz. Borbhetta Tea Estate, North Bank, Dikom & Nagrakata, West Bengal during the year 2017. The formulation was sprayed twice consecutively in 7 days interval @ 90 g a.i./ha (X) and 180 g a.i./ha (2X). Sampling was done at intervals of 0 (2 hr), 1, 3, 5, 7, 10 and 14 DAS. About 2 kg of tea shoots plucked on 0, 7, and 14 days after treatment was processed to CTC black tea and green tea at Tocklai. Samples of tea shoots, black tea, green tea and tea brew were analyzed for residues of spirotetramat and spirotetramat enol by a modified QUECHERS based LC-MS/MS method. The average recoveries of spirotetramat and its metabolite were found to be 76% to 120%. The half-life was found to be 2.53 & 2.32 days for single and double the recommended dose, respectively. The residues in black tea sample corresponding to 7day PHI were 0.21 to 2.71 mg/kg while the same in green tea was 0.30 to 2.00 mg/kg at recommended (X) dose. No residues were found in 14 D soil sample. Transfer rate of residues to tea brew were also very much limited.