Physical Modes of Action of Sterol-Inhibiting Fungicides Against Apple Diseases. Michael Szkolnik, Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Geneva 14456. Plant Dis. 65:981-985. Accepted for publication 24 March 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-981.

Sterol-inhibiting CGA 64251, bitertanol, fenarimol, fenapanil, prochloraz, triadimefon, and triforine were evaluated on apple in the greenhouse. Against Venturia inaequalis, they were more effective in eradicative than in protective action. They inhibited spore production when applied before scab symptoms appeared but not when applied to existing scab lesions. Against Podosphaera leucotricha, CGA 64251, bitertanol, and triadimefon sprays gave excellent protection. Vapor from CGA 64251 and triadimefon gave very good protection against mildew on unsprayed trees.