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Sour bunch rot


Sour rot is a wet rot that spreads rapidly throughout clusters and smells like vinegar. It is caused by acetic acid bacteria and various undesirable yeasts and fungi. Unlike Botrytis bunch rot, it usually lacks fungal sporulation. Low-grade powdery mildew infections and grape berry moth infestations can predispose clusters to infection. Fruit flies are common and help spread the disease. Tight-clustered cultivars are more susceptible than others. Prolonged periods of wetness or high relative humidity are conducive to sour rot development.

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The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.