Effect of fungicides on the numbers of micro-organisms and frequency of cellulolytic fungi in soils

Abstract

Fungicides were applied to both field and laboratory incubated soils, in order to determine their effects on fungal and bacterial numbers, and on the frequency of celluloytic fungi. In field soils, fungal numbers were initially reduced following the application of Captan, Dicloran, Milcol, and Triarimol, but then returned to the level of the untreated soil after 157 days. The major cellulolytic fungal species were generally unaffected, or increased in frequency in treated soils. Certain species includingTrichoderma koningii andPenicillium nigricans became dominant in treated soils, while species ofChaetomium andVerticillium decreased in frequency. Bacterial numbers increased in laboratory incubated soils which were treated with Captan. Fungal numbers however, were generally decreased, while the response of the actinomycete population depended on the concentration of fungicide applied.