Research has shown that if the mummies are left hanging in the vine they will release spores all summer long. If, however, the mummies are removed from the vine and deposited on the ground they will produce and release spores for 3-4 weeks only during May and June. If the mummies are disposed of by burial, or are removed from the vineyard, then no spores will be released. So, by simply removing the old rotted clusters from the vine growers can greatly reduce the potential amount of disease. Despite your best attempts at sanitation, however, some chemical applications are likely to be necessary, especially during wet years.
Wild grapevines are so common in Indiana that there are almost always some fungal spores around.
The primary strategy for controlling black rot involved applying fungicides. The proper material must be applied at the proper time to achieve satisfactory results. The best times to apply fungicides are during the early part of the season, specifically from just before bloom until about two weeks after bloom. These three sprays are the most important for controlling black rot. The best fungicides to control black rot in the home planting are captan, ferbam, copper, and Bordeaux mixture.