Residues and dissipation pattern of some insecticides in/on rapeseed

Residues and dissipation pattern of some insecticides were studied Oil rapeseed leaves and pods during the years 1999 and 2000. The study revealed insecticides recovery range of 83 to 91 per cent by bioassay and GLC. Recovery from cypermethrin fortified samples was highest whereas, it was lowest from malathion samples. Higher residues were found in leaves as compared to pods. The dissipation of cypermethrin and malathion was faster than dimethoate and methyl demeton. The initial deposits of cypermethrin, dimethoate, malathion and methyl demeton on rapeseed leaves were 2.60, 6.94, 12.38 and 3.75 mg/kg, respectively. However on the respective days, the initial deposits of cypermethrin, dimethoate, malathion and methyl demeton on rapeseed pods were 0.75, 2.51, 4.49 and 1.59 mg/kg. Almost all the residues of cypermethrin and malathion in leaves and pods dissipated on 7^th day. Residues of dimethoate and methyl demeton in leaves dissipated to the tune of 98 per cent on 15^th day.