A little mildew makes a lot of bad wine CALS Impact Statement uri icon


  • Abstract

    Grape growers need to control the powdery mildew to produce high-quality wine, without resorting to overkill, but how much powdery mildew is too much?


    Mere traces of powdery mildew were found to raise havoc with wine quality. The problem is not the small amount of mildew but rather the spoilage microbes that tag along and compete with desirable yeasts during fermentation. These microbes produce flavors in the finished wine that resemble cow manure and negatively affect wine quality.


    Cornell plant pathologists, entomologists, and enologists collaborated in a six-year project to untangle just how this occurs, and how to avoid it. Traces of mildew start the problem, and they somehow make the effected grapes more attractive to fruit-feeding insects. The insects injure the berries, and then the rotters arrive. The end result is contamination of the fermentation process and low-quality wine. The trace mildew infections occur about three weeks after bloom. Pinpointing this time has allowed them to be efficiently controlled, thereby preserving crop health, and insuring the wine will be the best.


    Consumers will remember a single bottle of contaminated wine long after they have forgotten several excellent vintages produced by the same winery. If this is their first experience with a particular winery, it will also likely be their last. Better grapes mean better wines, fewer complaints, more repeat sales, and an enhanced reputation for New York State vineyards.

    Funding Sources

    • Other USDA (e.g., Water Quality, Special Grants, NRI)
    • New York Wine and Grape Foundation


    • Dept. Food Science, Cornell University, NYSAES, Geneva, NY 14456.
    • Dept. Entomology, Cornell University, NYSAES, Geneva, NY 14456.

    Key Personnel

    • Robert C. Seem Professor, Dept. Plant Pathology, Cornell University, NYSAES
    • Wayne F. Wilcox Professor, Dept. Plant Pathology, Cornell University, NYSAES
    • Thomas Henick-Kling Professor of Enology, Cornell University, NYSAES
    • Mark Wagner Grape grower, owner and winemaker, Lamoreaux Landing Wine Cellars, Lodi, New York