Leaves are susceptible for about one week after they unfold. Petiole infection may cause the leaves to wilt. Shoot infection results in large black elliptical lesions. These lesions may contribute to breakage of shoots by wind. The fruit infection phase may result in substantial economic loss.
Berries are susceptible to infection from bloom until they begin to ripen.
An infected berry first appears light brown, soon the entire berry turns dark brown, and black pycnidia develop on its surface. Infected berries shrivel, turn hard and black and are called mummies. The black rot fungus overwinters in mummified fruit on the vine and on the ground. Spring rains trigger release of airborne ascospores from the mummies and infection of green tissue results if temperature and length of leaf wetness are conducive. Pycnidia form within lesions and produce pycnidiospores causing infection of green tissue if the requirements of temperature and leaf wetness duration are satisfied.