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Dimethirimol is a systemic fungicide that provides both protective and curative control of powdery mildew (Sphaeratheca fulginea) in cucurbits. Other uses include tobacco, tomatoes and ornamentals.

Fungicide.

ChEBI: A member of the class of aminopyrimidines that is 2-dimethylaminopyrimidine carrying methyl, butyl and hydroxy substituents at posiitons 4, 5 and 6 respectively. A fungicide first marketed in 1970, and used particularly in glasshouses to control powdery mi dew, it is no longer approved for use within the European Union.

Information presented in this summary is abstracted from unpublished data in the 1971 ICI dimethirimol petition submitted to the Canadian authority. Dimethirimol is rapidly metabolised in both plants and animals. Primary metabolic reactions in soils, plants and animals are N-dealkylation, hydroxylation of the butyl group and the direct conjugation of dimethirimol in plants (glucosides) and animals (glucuronides). Metabolic pathways are shown in Scheme 1.

Dimethirimol (1) is stable to heat and in acid and alkahe solutions. It is decomposed rather rapidly in aqueous solution when exposed to sunlight with an observed DT₅₀ of 7 days.