Black rot is caused by a fungus that is more or less present everywhere in the eastern and midwestern U.S. To control black rot of grapes, follow these steps: 1) Practice good sanitation during pruning. Remove all of the old fruit mummies that may be still hanging on the vine. These are the source of inoculum (spores) that are responsible for disease outbreaks in the coming season. It is best to remove them from the vineyard completely but just dropping them to the ground will help a lot. 2) Practice good canopy management during the growing season. Black rot, like most grape fungal diseases, requires a period of free moisture (leaf wetness period) on the surface of the leaves or fruit to cause an infection. Creating an environment around the fruiting zone of the vine that promotes more rapid drying of fruit and foliage after a rain or dew event decreases (not eliminates) the chances of an infection event occurring. Properly position the shoots by pulling them out perpendicular to the vine row, separating them out individually and breaking any tendrils that bind them together, and allow them to hang straight down toward the ground, each shoot occupying its own space (imagine neatly combing the canopy like you do hair). This is best done when the new shoots are about 18-24” long and may need to be repeated in mid- or late June. The idea is to try to avoid thick, matted canopies that trap moisture and humidity and provide a more ideal environment for disease infection to take place. 3) Finally, keep up a good protective spray program during the spring until about 5-6 weeks after the berries form. From the time the shoots are about 4 inches long, spray every 7-14 days (depending on how much it rains). Contact your local cooperative extension office for fungicide recommendations for your area.

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