The Mechanism of Action of the Fungicide, 2-Heptadecyl-2 4rnidazoline

owe its effectiveness to interference with the synthesis of histidine or purines was tested in experiments with Sclerotinia fructicola. The toxicity of the fungicide was significantly decreased by guanine, xanthine, or xanthosine; a number of other related compounds and histidine had no effect. Annulment of the action of 2-heptadecyl-2-imidazoline by either xanthine or guanine was competitive. The inhibition index for 2-heptadecyl-2-imidazoline/ xanthine was 0*000581, while that for 2-heptadecyl-2-imidazoline/guanine was 0-000832. Attempts to demonstrate the accumulation of the purine precursor 5-amino-4-imidazolecarboxamide in culture filtrates of Sclerotinia fructicola grown in the presence of the fungicide were negative. Despite the wide use of many organic fungicides, little information is available concerning their mechanism of action (Horsfall, 1945). The present report is concerned with 2-heptadecyl-2-imidazoline(2-heptadecyl-2-glyoxalidine), the active ingredient of Crag Fruit Fungicide 341, manufactured by the Carbide and Carbon Chemicals Company, New York. This material is widely used i