On stems, infection appears as reddish-brown spots or streaks. Anthracnose is caused by the fungus Gloeosporium . The fungus can cause lesions on stems, leaves, bud scales, and flowers. Stem lesions range from small spots to elongated cankers several inches long. These cankers are often gray to black in color, but may be covered with the growth of salmon colored fungal spores.
Cankers can girdle and kill stems.
The anthracnose fungus also may cause irregular brown spots on leaf tissue, resulting in leaf curling and puckering. Infection of bud scales and petals interferes with flower develpment. The fungus Botrytis cinerea may also infect stems, leaves, and buds. In wet weather, diseased plant parts become covered with a brown to gray coat of fungal spores. Stems, leaves, and buds when infected suddenly wilt and turn black color.