Persistence of Cypermethrin on Stored Pulses and its Decontamination

The persistence of cypermethrin on blackgram (Phaseolus mungo Roxb.), chickpea (Cicer arietinum Linn.), cowpea (Vigna synensis L. Savi ex. Hassk.) and lentil (Lens culinaris Medik syn. L. esculenta Moench.) was studied under laboratory conditions. The grains were treated at 3 and 5 mg kg⁻¹ levels of cypermethrin and stored for six months. The high recovery of extractable residues of cypermethrin in all the pulses revealed its high persistence (62–71% of the applied insecticide) after 6 months of the treatments. Dissipation of cypermethrin was biphasic with initial rapid decline upto 3 months followed by a phase of slow and steady dissipation. Decontamination processes like washing and steaming dislodged the residues by 37 to 49% and 63 to 74%, respectively. Maximum concentration of cypermethrin was found on seed coat only. However, the treatments did not reduce the germinability of the treated pulse grains.