Latin name: Godronia cassandrae, asexual: Fusicoccum putrefaciens
Reason for Concern:
1) Can interfere with establishment of new.
2) It is the most serious canker disease of blueberry in British Columbia.
3) Branches on affected plants are killed, reducing yields. Plants will die if too many branches are killed.
4) It is less serious in established fields because only new wood can be infected.
Early symptom is flagging, or sudden wilting and death of 1 stem during warm summer. Flagging is caused by 1 or several cankers completely encircling the stem. The leaves turn reddish-chocolate brown and will remain attached to the branch. Stem cankers begin in the fall as small, water-soaked lesions on green stems around buds and wounds, turning red by December. In spring, the lesions expand into sharply delineated, reddish brown cankers that usually center on a leaf scar, are 1 to 10 cm in length, and have a bulls-eye pattern. Most cankers are near ground level, but some occur as high as 3 feet (1 m). As cankers enlarge, their centers turn gray and their margins remain reddish to dark brown. Small, black fruiting bodies of the fungus may be found in the center of older cankers. Cankers become larger each year. The stem wilts and dies when the canker girdles the stem.
The fungus overwinters in cankers on infected bushes. Only new wood can be infected. Wounding is not required for infection. Spores produced by fruiting bodies are dispersed by splashing water, rain, and overhead irrigation, from bud swell until early leaf drop in the fall. Infection usually occurs between bud break and flowering when there is young tissue, although new infections can occur anytime between late spring and early fall. Spores infect stems primarily at leaf scars from March through June. Natural openings in bark also may serve as infection sites. Spores also are produced and released from August through October but probably account for few infections. This disease is favored by wet weather and temperatures between 50° to 72° F. On wet canes, infection occurs within 48 hours. This disease is also known as Fusicoccum canker.