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Ripe Rot of Muscadine Grape Caused by Colletotrichum gloeosporioides And Its Control. M. E. Daykin, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650; R. D. Milholland, professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 74:710-714. Accepted for publication 18 February 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-710.

Colletotrichum gloeosporioides, the cause of ripe rot of muscadine grape (Vitis rotundifolia), was isolated from mummies, pedicels, and fruit spurs of grape during the winter months of 1979, 1980, and 1982. Infected mummies and pedicels produced abundant conidia during rainy periods in the spring and served as sources of primary inoculum. Conidia of C. gloeosporioides were trapped regularly in rainwater runoff from grapevines from March through October 1981 and 1982. Most conidia were caught in the early spring of 1981, when many overwintered mummies remained on the vines, and in the fall of both years, when ripe, rotting fruit were present. Inoculations of immature fruit on the vine, as well as isolations from naturally inoculated green fruit, indicated that infections by C. gloeosporioides occur at all stages of fruit development. These infections are probably latent, because symptoms do not appear until ripening. A fungicide bioassay showed that captafol, followed by captan, maneb, and benomyl, had the most activity against C. gloeosporioides. Etaconazole and triforine were neither fungistatic nor fungicidal at 20 and 500 μg/ml, respectively. In field tests, captafol, folpet, captan, and maneb suppressed the level of ripe rot when applied every 2 wk from bloom until near harvest.