ACCELERATED DEGRADATION OF FENAMIPHOS AND ITS METABOLITES IN SOIL PREVIOUSLY TREATED WITH FENAMIPHOS

The degradation of fenamiphos, fenamiphos sulfoxide, and fenamiphos su lfone was determined in a greenhouse experiment using autoclaved and n onautoclaved soil from field plots treated or not treated with fenamip hos. Fenamiphos degradation and formation of fenamiphos sulfoxide was faster in nonautoclaved soil than in autoclaved soil. In nonautoclaved soil, previous exposure to fenamiphos was associated with increased r ate of degradation of fenamiphos sulfoxide. Fenamiphos total toxic res idue degraded more rapidly in nonautoclaved soil previously exposed to fenamiphos than in nonautoclaved soil never exposed to fenamiphos. Th is accelerated degradation was due to more rapid degradation of fenami phos sulfoxide and appears to be biologically mediated.