PERSISTENCE OF PERMETHRIN AND WL-43775 IN SOIL

Six soils, fortified with permethrin or WL 43775 at 1 mg/kg, were incubated for 16 weeks at temperatures alternating between 20 °C for 15 h and 10 °C for 9 h. Initially and at 4-week intervals soils were sampled and analyzed. In five of the soils degradation of both insecticides was rapid, resulting in half-lives of approximately 3 weeks for cis-and irans-permethrin and 7 weeks for WL 43775. In the other soil very little degradation occurred: recovery after 16 weeks was greater than 75% for cis-permethrin and WL 43775, slightly less for trans-permethrin. Sterilization of two of the soils in which degradation was rapid greatly reduced the rate, indicating that microbial degradation was the chief factor in loss of these insecticides. © 1979, American Chemical Society. All rights reserved.