Bunch Rot

Bunch rot in grapes occurs during fruit ripening. Early season shoot blight may occur following prolonged warm moist conditions caused by frequent spring rains. At veraison, individually infected berries in a cluster turn brown on white cultivars or reddish in red and black cultivars. If temperatures are moderate, moisture is high, and wind speed is low, epidermal cracks will form in which fungal growth produces mycelium and spores, resulting in the characteristic grey, velvety appearance of infected berries.