Butternut Canker Biology
Spores of the causal fungus are disseminated from fruiting bodies by rain splash and insects. Produced throughout the growing season, the spores can survive and be dispersed long distances during cool weather. The fungus enters the host via leaf scars, buds, and bark wounds (Tainter and Baker 1996). Branch cankers caused by the fungus usually occur first in the lower crown, and stem cankers develop later from spores washing down from cankers above. Cankers are elongated sunken areas, often with an inky black center and whitish margins. Brown-to-black elliptical areas of killed cambium can be seen under peeled bark. Older branch and stem cankers are perennial, often covered by shredded bark and bordered by successive callus layers (Hoffard and others 1995). The cankers eventually girdle the tree, moisture stressing the tree. The canopy becomes thin or dies back and the tree eventually dies. Nuts produced from infected trees are usually not viable, limiting reproduction of this rare tree.
High mositure levels favor the spread and impact of this disease. The high humidity favors high spore germination and spore production may continue for up to 20 months on dead host tissue (Tainter and Baker 1996).
Encyclopedia ID: p1428
