Bunch rots—Botrytis cinerea and other factors
Symptoms of bunch rot often appear first on old flower parts and spread to fruit and foliage. Leaves,
flowers, and green or ripe fruit on or near the soil in the dampest or densest areas of the canopy turn
light brown and develop a gray or brown fuzzy growth of fungal spores. Occasionally stems may be affected.
Fruit or plants shrivel and rot and often develop flattened, hard, black masses, called sclerotia, under
Use planting densities and training
techniques that provide maximum air movement through the plant canopy.
Avoid excessive nitrogen fertilizer that will encourage excess growth. Trim leaves around bunches soon
after bloom to improve air circulation. Remove diseased plants as soon as they appear, and pick ripened
grapes as soon as possible. Harvest fruit in advance of rainy or humid conditions when possible. Fungicides
are available but should not be needed if leaves are pruned and no rains occur during bloom. Chemicals
are not recommended for summer bunch rot.
Early spring infection on leaf