Distinctive symptoms differentiate four common types of berry shrivel disorder in grape

S berries on ripening clusters are not uncommon in California vineyards. They usually occur in only a small proportion of a vineyard’s fruit (1% to 5%), but in particular vineyards and years, shriveling can affect more than half of the crop (M. Krasnow, unpublished observation). Most shrivel disorders make the fruit less desirable for winemaking, with subsequent yield and production losses. Before taking steps to reduce the incidence of fruit shriveling in vineyards, it is necessary to differentiate between shrivel disorders. We describe four common causes of fruit shriveling and detail compositional differences between normally developing fruit and that affected by sugar accumulation disorder (SAD).