Metalaxyl (Apron 35SD), used as a seed treatment, was highly effective in controlling sorghum downy mildew of maize induced by Peronosclerospora sorghi. Plants grown from seeds treated with metalaxyl, or any mixture containing metalaxyl, remained free from the disease and had significantly higher grain yield than plants grown from seeds treated with thiram-based fungicides or from untreated seeds. A dosage of metalaxyl as low as 0·35 g a.i./kg seed gave complete control of downy mildew.