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No Cure for Nuts
In a nutshell: Butternut canker has no known cure, chemical or organic, but if you keep your tree healthy, it can live with the disease for years.
The whole story: The butternut (Juglans cinerea) is a hardwood native to the eastern half of the United States and is closely related to the black walnut (J. nigra). The tree is valued for its delicious nuts, which are high in antioxidants, and excellent quality wood. In 1967, scientists first discovered that a previously unknown fungus, butternut canker (Sirococcus clavigignenti-juglandacearum), was killing butternut trees. Today, butternuts are dying all across their range and have been declared an endangered species in Ontario and a "species of concern" in many U.S. states.
The spores of butternut canker spread via wind and rain splatter, insects, and probably birds. "It enters the tree through small insect feeding wounds, leaf scars, and cracks in the bark," says Michael Ostry, a researcher at the USDA Forest Service, North Central Research Station, in Minnesota. The fungus causes cankers to develop. The cankers gradually increase in number and eventually girdle the tree. The disease often goes unnoticed because the infection generally begins in the crown of the tree and then moves downward.
There's no way to prevent the canker from infecting a tree, and "unfortunately, there is no feasible control at this time," says Ostry. He and his colleagues are currently monitoring potentially resistant trees and working to develop a resistant cultivar. He recommends that homeowners keep their trees healthy (keep them watered so they don't become stressed by drought, and faithfully prune out dead or damaged wood) and monitor them. It usually takes several years for the disease to kill the tree, so Ostry doesn't recommend cutting an infected tree down until it stops producing nuts or becomes a hazard.
If you have a healthy butternut tree with a trunk 3 feet or more in circumference that's growing near infected trees, Michael Ostry would like to monitor it. You can contact him at the USDA Forest Service, North Central Research Station, 1561 Lindig St., St. Paul, MN 55108, 651-649-5113, or via e-mail at mostry@fs.fed.us.
