Cypermethrin Insecticide Residues in Vegetable Soybean, Glycine max (L.) Merrill, at Different Days of Pre-harvest Interval

Abstract

The experiments were conducted to investigate cypermethrin insecticide residues in vegetable soybean at different days of pre-harvest interval for two growing seasons. Soybean pods were collected at 0, 1, 3, 5 and 10 days after last application with cypermethrin. Residues were extracted from pods and determined using gas liquid chromatography with an electron capture detector. Cypermethrin when applied at the rate of 100 g ai/ha using a knapsack sprayer showed a mean residue level of 0.71 and 0.52 mg/kg at 0 and 1 day, respectively, in dry season (December- February) whereas the residues were 1.62 and 1.17 mg/kg at 0 and 1 day, respectively, in early wet season (April-June). A pre-harvest interval of 3 days was found safe (0.42 mg/kg) for consumers in dry season whereas early wet st season soybean exhibited residue level of 0.48 mg/kg at 10 day which fell below maximum residue limit of 0.5 mg/kg as prescribed by Food and Agriculture Organization/World Health Organization. Therefore, a pre-harvest interval of 10 days should be considered for cypermethrin residues in vegetable soybean to avoid any health risk of consumers. The dissipation rates of cypermethrin on soybean pods were more or less similar at the same days for both seasons which was 70% (based on 0 day) at 10 days.