Symptoms
Small, water-soaked lesions develop on green stems in the fall and expand into sharply delineated, reddish brown cankers during the following spring and summer. The cankers usually center on a leaf scar, are 1 to 10 cm in length, and have a bull’s-eye pattern. Most cankers are near ground level, but some occur as high as 3 feet (1 m) above the ground.

Cankers enlarge each year until they girdle and kill the stem. Wilted leaves remain attached. Small, black fruiting bodies of the fungus may be found in cankers.

Disease cycle
The fungus overwinters in cankers and produces fruiting bodies (pycnidia) from which spores are released during rain events from bud swell until early leaf drop in the fall. Wounding is not required for infection. On wet canes, infection occurs within 48 hours at 50 to 71ºF (10 to 22ºC). Ascospores are relatively unimportant in the disease cycle.

Management
Remove and destroy stems with cankers; avoid susceptible cultivars; limit overhead irrigation; apply effective fungicides.