Residual behaviour of endosulfan,chlorpyriphos and chlorpyriphos methy1 in pigeon pea, Cajanus cajan (L.) Millsp.

Investigations were carried out to evaluate the residue behaviour of endosulfan, chlorpyriphos and chlorpyriphos methyl sprayed at their recommended dosage at initiation of flowering in pigeon pea. Quantitative estimation of all the residues of three insecticides revealed chlorpyriphos with higher initial deposition of 0.631 μg/g in leaves. A rapid decrease from high initial deposition was observed for chlorpyriphos and chlorpyriphos methyl wtihin 3 days. Chlorpyriphos methyl, a newer insecticide showed lower residual deposition on leaves after each spray with a rapid reduction up to 50% within 3 days. However, the residue concentration of all the three insecticides were below the limit of detection in leaves and pods after third spray collected at final harvest. In grains, chlorpyriphos methyl gave the lowest residual concentration of 0.046 μg/g followed by chlorpyriphos and endosulfan, 0.063 μg/g and 0.110 μ/g, respectively. Half lives of endosulfan, chlorpyriphos and chlorpyriphos methyl in the leaves of pigeonpea varied from 2.9 to 4.3 days, 2.6 to 3.7 days and 2.3 to 4.3 days, respectively.