Cultural Practices for Disease and Insect Control
Always plant in a well-drained location with all-day sun (no shade). Black rot is the most common disease home gardeners encounter when producing grapes. Berries infected by the black rot fungus turn into dry, shriveled, raisin-like "mummies." The black rot fungus overwinters in the planting in these old, mummified fruit. Therefore, it is essential to remove all clusters of mummified fruit from the planting, as well as those that have fallen to the ground. This is best done at harvest or soon after, while they are still easily visible.
If black rot lesions appear on leaves before fruit set, removing infected leaves should reduce the level of infection.
Most fungi require water on plant surfaces to infect. To promote rapid drying conditions within the foliar canopy, keep the vines well pruned (during the dormant season), trellised and weed-free.
Several pickings will be necessary at harvest because not all of the grape bunches will ripen at the same time. Harvesting in this manner reduces the incidence of yellow jackets, bees and wasps feeding on overripe fruits, and discourages the rot organisms from becoming established. Remove all old dried or rotted unharvested grapes (including cluster stems) from the vine and destroy them. Collecting and destroying leaf debris under vines in the fall may help reduce overwintering pupae of the grape berry moth. Pick off and destroy Japanese beetles daily.
Table 17. Spray Schedules for Pest Control on Grapes.