Delayed and Enhanced Degradation of Benomyl and Carbendazim in Disinfested and Fungicide-Treated Soils

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Abstract
Factors affecting the biodegradation of benomyl and of its fungitoxic hydrolysis product, carbendazim, in soil were studied. Soil disinfestation by fumigation or solarization prior to fungicide incorporation inhibited degradation and extended the persistence of carbendazim in soil. Carbendazim was present for a significantly longer time and at higher concentrations in leaves of pepper grown in a field soil disinfested and treated with benomyl than with plants grown in nondisinfested soil. The fungicides TMTD (thiram) and fentin acetate strongly inhibited the degradation of carbendazim, when added to the soil with carbendazim. A drastic reduction in general enzyme activity in soil amended with TMTD was observed. Alternaria alternata and Bipolaris tetramera, which are capable of degrading carbendazim, were isolated from the soil. The 2 fungi were sensitive to low concentrations of TMTD and fentin acetate. The combined application of TMTD with benomyl in the field, intended to prolong the biological activity of benomyl, further reduced the number of apothecia of Sclerotinia sclerotiorum compared with benomyl treatment alone. In soil with a history of benomyl treatment, carbendazim was degraded more rapidly than in a soil without such a history.