Generally, vinifera are much more susceptible to bunch rot, with the white varieties more susceptible than the reds. Canadice and Romulus are very susceptible. Any tight clustered variety is likely to have Botrytis problems. Good air circulation throughout the canopy is critical in controlling this disease. F is optimum, however, this fungus can germinate over a wide range of temperatures.
Moisture is necessary for germination.
Leaves are susceptible for about 1 week after they unfold. Black rot is generally considered an early-season disease since all green tissue is susceptible and fruit is susceptible up until veraison. Symptoms on fruit usually will occur prior to veraison. Infected berries turn from light brown to dark brown, then shrivel and turn hard and black. The hard black mummies remain firmly attached to the cluster.