Residues of Thiamethoxam 12.6%+ Lambda Cyhalothrin 9.5%ZC in Vegetable Cowpea

A field experiment was conducted to study the rate of dissipation of insecticide mixture (thiamethoxam 12.6%+ lambda cyhalothrin 9.5%ZC) in vegetable cowpea. The insecticide mixture @ 0.30 ml l^-1 was sprayed at pod formation stage, and samples of pods were harvested at 0 (2 hr after spray), and 1, 3, 5, 7, 10, 15 days after spray. The residues were estimated using liquid chromatography tandem mass spectrometer (LC MS/ MS) and GC-ECD at the All India Network Project on Pesticides Residues, College of Agriculture, Vellayani, Kerala. The residues of thiamethoxam and lambda cyhalothrin were found to be 0.12 and 0.21 µg g^-1, respectively. Residues were observed to persist up to three days, and were below detectable level on the fifth day.