BIOLOGICAL-CONTROL OF SPORIDESMIN-PRODUCING STRAINS OF PITHOMYCES-CHARTARUM BY BIOCOMPETITIVE EXCLUSION

The feasibility of using atoxigenic strains of Pithomyces chartarum fo r the biological control of toxigenic strains of P. chartarum was exam ined. Pasture, treated with atoxigenic strains of P. chartarum, contai ned up to 80% less sporidesmin than found in untreated pasture. Maximu m sporidesmin levels of 26 ng g(-1) grass in treated pasture and 113 n g g(-1) grass in untreated pasture (means of 24 and four plots, respec tively) were recorded 14 weeks after treatment, when spore numbers had reached a maximum of 80 000 spores g(-1) grass in the untreated plots and 50 000 spores g(-1) grass in the treated plots. This trial demons trated that sporidesmin-producing spores of P. chartarum could be succ essfully reduced in pasture by the addition of atoxigenic strains, the reby reducing the risk of facial eczema in livestock.