Butternut Canker Disease:
Butternut or white walnut is being killed throughout its range by Sirococcus clavigignenti-juglandacearum, a fungus that was probably introduced into North America in 1967. The fungus initially infects trees through buds, leaf scars, and other openings in the bark. Spores produced on branches are carried down the stem by rain, resulting in multiple, perennial stem cankers that eventually girdle and kill infected trees. Very little can be done after the canker has infected the tree.
Butternut Canker Disease Description:
Young, annual cankers are elongated, sunken areas commonly originating at leaf scars and buds, often with an inky black center and whitish margin. Under the bark, the fungus forms pegs that break through the outer bark surface, exposing the spores. Peeling the bark away reveals the brown to black elliptical areas of killed cambium. Older, perennial branch and stem cankers are often found in bark fissures, or covered by bark and bordered by successive callus layers. Cankers develop throughout a tree, but commonly occur on the main stem, at the base of trees and on exposed roots.
Species Host:
Attacks
butternut or white walnut
Managing The Canker:
Butternut is a relatively short-lived tree, and stress from old age and competition often leads to root diseases, decays, infection by other fungi, and invasion by wood-boring insects, resulting in tree death unrelated to butternut canker. If butternut canker is responsible for the loss of crown volume, there is almost always evidence of stem canker. The best management strategy is to improve health in single tree and stands using proper pruning and tree care.
