Residue dynamics of some insecticides in cabbage and soil

Persistence of imidacloprid, λ-cyhalothrin and spiromesifen on cabbage head and soil was studied. Two foliar applications of imidacloprid, λ- cyhalothrin and spiromesifen @ 25, 15 and 96 g ai ha^-1 (single dose) and 50, 30 and 192 g ai ha^-1 (double dose), respectively, were given at 10 days interval. Treated samples were processed by using modified QuEChERS method and the residue data was subjected to statistical analysis. Studies revealed that the initial deposits of imidacloprid, λ- cyhalothrin and spiromesifen were 0.39, 0.20 and 0.74 mg kg^-1 for single dose and 0.80, 0.41 and 1.58 mg kg^-1 for double dose, respectively. Among three insecticides, spiromesifen was the most persistent insecticide (10 days for both doses) followed by λ-cyhalothrin (7 and 10 days) and imidacloprid (5 and 7 days) on cabbage head. The safe waiting period for imdacloprid, λ- cyhalothrin and spiromesifen were 5, 6 and 9 days for single dose and 6, 7 and 11 days for double dose with the half life of 1.6, 2.5-3.1 and 1.8-1.9 days, respectively.