Methyl benzimidazol-2-ylcarbamate,the fungitoxic principle of thiophanate-methyl

A correlation was found between the formation of benzimidazol-2-ylcarbamate esters from the thiophanate fungicides [thiophanate, thiophanate-methyl and 2-(3-methoxycarbonylthioureido)aniline] and the fungitoxie activity of these fungicides. Fungitoxic activity of the thiophanates is increased by ageing in aqueous media while fungitoxicity as well as conversion rate decrease at lower pH. It is concluded that it is not the thiophanates themselves but the corresponding benzimidazol-2-ylcarbamate esters that are responsible for the fungitoxic effect. Hence thiophanate-methyl, like benomyl, is a precursor of the fungitoxic agent methyl benzimidazol-2-ylcarbamate (MBC). Indications were obtained that fungal metabolic activity can increase the rate of conversion of thiophanate-methyl into MBC.