Persistence of chlorfenvinphos in soils

The persistence and behaviour of chlorfenvinphos, an organophosphorus insecticide, was studied on different soils. On a peaty soil the insecticide was only very slowly degraded, there being 70% of the applied dose remaining after 21 weeks and 30% after nearly 12 months. On the sandy soils, however, persistence was much shorter; between 3 and 15% of the applied dose remained after a period of 15 weeks. Rates of loss appear to be related to soil moisture conditions; in dry seasons, although the initial rate of loss was high, subsequent rate of breakdown was slower than in wetter seasons. The results are discussed relative to the efficiency of the insecticide for controlling brassica root fly.