Postinfection and Antisporulant Activities of Selected Fungicides in Control of Blossom Blight of Sour Cherry Caused by Monilinia fructicola. W. F. Wilcox, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. . Plant Dis. 74:808-811. Accepted for publication 10 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0808.

Nine fungicides—captan, fenarimol, flusilazole, iprodione, myclobutanil, propiconazole, tebuconazole, triforine, and vinclozolin—were tested for ability to prevent infection of sour cherry (Prunus cerasus) blossoms when applied 24, 48, or 72 hr after inoculation with different levels of Monilinia fructicola. When applied 24 hr after inoculation with a suspension containing 5,000 conidia per milliliter, all fungicides gave 86–100% control of blossom blight (relative to untreated checks), and all fungicides except captan gave 97–100% control following inoculation with 50,000 conidia per milliliter. However, when sprays were applied 48 hr after inoculation with 500, 5,000, and 50,000 conidia per milliliter, the degree of control was 84–100%, 57–98%, and 7–82%, respectively. When sprays were applied 72 hr after inoculation with 500 conidia per milliliter, control was only 16–64%, and when the inoculum level was 5,000 conidia per milliliter, virtually no control was provided. When blossoms were sprayed with the same fungicides 72 hr after inoculation with 50,000 conidia per milliliter and incubated an additional 4 days at 95–100% relative humidity, all became necrotic, but conidium production was reduced by 51% (captan) to 100% (vinclozolin), relative to unsprayed blossoms. At the dosage rates tested, vinclozolin, iprodione, tebuconazole, and propiconazole were the most effective fungicides in both the postinfection and antisporulant modes, whereas captan was the least effective.

Keyword(s): brown rot, ergosterol biosynthesis-inhibitor fungicides, sterol-demethylation-inhibitor fungicides, sterol-inhibitor fungicides, triazole fungicides.