Persistence of some Synthetic Pyrethroids in/on Cabbage

Persistence of cypermethrin, decamethrin, fenvalerate and fenpropathrin emulsions has been studied on cabbage heads. At their recommended dosages, the synthetic pyrethroids resulted in initial deposits of 4.20 and 3.24 ppm, 1.56 and 0.80ppm, 2.91 and 2.94 ppm, and 2.87 and 2.71ppm, on cabbage heads, with the proprietary and laboratory prepared formulations respectively. After 3 d of application, the residues dissipated to 2.33 and 1.88 ppm, 0.97 and 0.55 ppm, 2.02 and 2.08 ppm, and 1.81 and 1.61 ppm, working out to 44.52 and 41.98, 37.82 and 31.25, 30.58 and 29.25, and 36.93 and 38.01%dissipa-tion in case of proprietary and formulated cypermethrin, decamethrin, fenvalerate and fenpropathrin, respectively. The half lives were 2.25 and 1.97 d, 2.48 and 2.47 d, 3.14 and 3.68 d and 4.26 and 3.85 d respectively. The persistence pattern of their residues, yielded waiting periods of 6.10 and 5.17 d, 8.89 and 6,66 d 8.89 and 10.19 d, and 6.86 and 5.98 d for the proprietary and laboratory prepared formulations of cypermethrin, decamethrin, fenvalerate and fenpropathrin, respectively, which clearly indicated the effect of the formulation recipe on the persistence of insecticides.