It overwinters in in old cane lesions or mummified berries in the vine or on the ground. In spring, spores are dispersed by wind and rain. Secondary infections are spread by rain splash.
Symptoms appear approximately 2 weeks after infection. Small reddish-brown circles on leaves, long dark lesions on petioles and shoots. Berries go from light brown to dark brown to hard black raisin-like bodies that remain on the cluster.
Primary infection from ground mummies occurs 2 to 3 Weeks After Bud Break until 2 weeks after bloom, however, mummies that remain in the vine and old cane lesions can infect up to veraison. Young leaves are susceptible until they completely unfold and finish expanding. Berries remain susceptible until 6 to 7 weeks after bloom and become completely resistant after veraison. Infection requires at least six hours of leaf wetness, or more, depending on temperature.
Remove all mummies from the canopy and vineyard floor after harvest and remove as much infected cane as possible during annual pruning. Critical Spray period – two weeks prebloom through four weeks postbloom. Sprays will not eliminate existing Black Rot, they will only prevent spread.