Residues of some synthetic pyrethroids and endosulfan in/on pigeon pea, Cajanus cajan (L.) Millsp*

Residues of cypennethrin, fenvalerate, deltamethrin and endosulfan onlin pigeonpea, Cajanus cajan (L.) Milsp. were determined at 0 (lh) 3, 5, 7 and 9 days after spraying; and pod shell and seeds at harvest. The residues were estimated by GLC with Ni63 electron capture detector. The initial deposit was 0.029, 0.096, 0.087 and 1.436 μg g−1 for cypermethrin (45 g a.i.), fenvalerate (60 g a.i), deltamethrin (15 g ai) and endosulfan (525 g a.i/ha). Deltamethrin residues were detected on plant only up to 7th day, while the residues of other insecticides persisted till the 9th day after spraying. The order of dissipation was deltamethrin > endosulfan > cypermethrin > fenvalerate with half life values as 1.5, 1.7, 1.8 and 3.43 days, respectively. At harvest, residues of cypemethrin and endosulfan were detected in pod shell while in seed samples, residues of only endosulfan were present. A waiting period of three days was suggested for all the insecticides.