Sour bunch rot

Sour bunch rot - Bacteria, yeasts and fungi
Annemiek Schilder, MSU Plant Pathology

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.


Photo: A. SchilderLeaky, collapsing berries with fruit fly larvae.	Photo: T. Zabadal

Additional information

Search MSU Fruit CAT Alert newsletter for articles.MSU Diagnostic Services
Special grape disease problems and controls (from Michigan Fruit Management Guide) (Download Adobe Acrobat Reader to view PDF files)

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Funding for this web site provided by Project GREEEN, American Farmland Trust, EPA Region 5's Strategic Agricultural Initiative program, The National Foundation for IPM Education, the Center for Agricultural Partnerships and the MSU Integrated Pest Management Program
in collaboration with MSU Extension and the Michigan Agricultural Experiment Station.
Updated 11/30/07 Contact: J.N. Landis.