Powdery Mildew of Grapes

(also odium disease of grapes), a disease of grapes caused by the powdery mildew Uncinula necator and characterized by the formation of a grayish white powdery coating on all surface organs of the plants. The infected leaves and sprouts become brittle and dry out prematurely, and the fruits usually crack, exposing the pulp, which soon rots. Wine from vineyards infected with powdery mildew sours rapidly and has a low alcoholic content and an unpleasant taste. The disease is found in all countries that engage in viticulture.