Evaluation of Insecticides against Onion Thrips (Thrips tabaci Lindeman) and Estimation of Carbaryl Residues in/on Onion
Relative efficacy of six insecticides viz., quinalphos, carbaryl, endosulfan, lindane, malathion and parathion spray was evaluated against the thrips, Thrips tabaci L. infesting onion. Significant control was obtained by 0.25% carbaryl and 0.05% endosulfan 3 and 7 days after spraying. The residues in/on onion leaves, bulbs and soil were also estimated for carbaryl on 3.5 months old onion crop. The initial deposits of 48.575,120.813 and 233.563 ppm resulted from 0.1, 0.25 and 0.5% carbaryl spray on onion leaves reached below detectable level in 30, 30 and 35 days respectively. The residues dissipated faster upto 7–10 days and reached below the tolerance limit of 10 ppm in 10, 20 and 30 days from the corresponding three dosages. The half-life values were 4–6 days and there was no translocation of residues into bulbs.