Butternut Canker

Butternut is a small to medium sized tree. Butternut typically is mixed with other hardwoods such as black walnut in the upland northern hardwood forest type (mapped as ‘maple-beech-birch’, ‘oak-hickory’, and ‘oak-pine’). Primarily found in riparian areas, this species was a significant producer of mast for wildlife. It hybridizes with other Juglans spp. such as heartnut, Japanese walnut, English walnut, little walnut, and Manchurian walnut. Although butternut is seldom found growing in great numbers, there is a strong desire to maintain a viable butternut population to preserve biodiversity (Clark 1965).

Butternut Canker

Butternut is being killed throughout its range in North America by a fungus, Sirococcus clavigignenti-juglandacearam. The fungus causes multiple cankers on the main stem and branches. Butternut canker has been found in 55 counties in the Southern United States. Butternut numbers have been dramatically reduced and it is now a candidate for listing under the Endangered Species Act.

Butternut canker is a fungal disease that has caused massive amounts of butternut mortality. The origin of the disease is unclear but known butternut canker history begins in 1967 in Wisconsin. The disease quickly spread into the southern Appalachians where most (up to 90% is some areas) of the butternuts were killed (butternut canker biology). This disease is spread by air, rain splashes, and insects. Once infected, a tree produces oozing cankers that can girdle and kill the tree. Butternut canker kills trees of all ages. Trees in all settings and ownerships appear to be equally affected, except in urban settings that have been fertilized (Fleguel 1996, Nicholls 1979).

Since butternut makes up less than 0.5 percent of the trees in the South, the overall impact of its loss to the forested ecosystem is considered by some to be minor. However, as butternut trees die, they are replaced by other species with a subsequent loss of biodiversity. Butternut canker management options are few but promotion of seemingly genetically resistant trees provides hope of maintaining butternuts as part of the ecosystem.