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Sour bunch rot - Bacteria, yeasts and fungi
Annemiek Schilder, MSU Plant Pathology
Home > Scouting guide> sour bunch rot 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.
Sour bunch rot Sour bunch rot
Photo: A. SchilderLeaky, collapsing berries with fruit fly larvae. Photo: T. Zabadal
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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. Partially support from NC-IPM Center.

05/26/11 Contact: E. Haney
     
Michigan Agricultural Experiment Station Michigan State University Extension