The persistence of deltamethrin on blackgram (Phaseolus mungo Roxb.) during storage was studied under laboratory conditions. The grains were treated at 2 and 3 mg/kg levels of deltamethrin and stored for six months. The recovery of 1.44 and 2.11 mg/kg extractable residues after 6 months of treatment revealed its high persistence (74–75% of the applied insecticide). Dissipation of deltamethrin was biphasic with an initial phase of rapid decline upto 2 months followed by a phase of slow and steady dissipation. Culinary processes like washing and steaming dislodged the residues by 40 to 60% from treated grains. Steeping of the grains in water and deskinning thereafter made the cotyledons free of residues. Maximum concentration of the insecticide was found on seed coat only and no metabolic and degradation products were found during the experimental period. The treatments did not reduce the protein content and germinability of grains.
Deltamethrin, persistence, residues, blackgram, decontamination
