Not ten feet out my office window stands a dying American Elm tree. Ten feet to the left of this dying tree is another elm that is already dead. Not 6 weeks ago these trees were alive and doing well. That’s how fast Dutch Elm disease claims the lives of these wonderful trees. But the occurrence of Dutch Elm is old news. Are you aware of the Butternut Canker disease? Its worse than Dutch Elm.
The Butternut tree (Juglans cinerea) is a highly valued deciduous tree native to the eastern US. It is sometimes called White Walnut because it is closely related to Black Walnut and has nearly white wood. Its wood is very strong and is sought by woodcarvers and cabinet makers worldwide. In addition, the abundant nut crop is a very important food source for all sorts of wildlife including White-tailed Deer and Turkeys.
Its common name comes from its butter-like oil, which some Native Americans once extracted from the nuts. The nuts (fruit) are egg-shaped or sometimes oval, and are 2-3″ in length and grow in tight clusters. Each nut is covered with a sticky green husk that turns brown upon maturing. The husks surrounding the nuts were often used to dye fabrics. During the Civil War, the color of the Confederate uniforms was created using butternut husks.
Currently, all the butternut trees in the entire eastern US are being devastated by an exotic fungal disease that causes branch and stem cankers and ultimately death. The name of this fungus is Sirococcus clavigignenti- juglandacearum, a mitosporic fungus that belongs to a large group of fungi called Fungi Imperfecti. It was first described in Iowa in 1967 but is believed to have spread to Iowa from southeastern U.S. some forty of fifty years prior.
In 1995, the Forest Service estimated that 75 percent of all butternuts in the southeastern U.S. were dead with the remaining trees heavily infected and no longer reproducing. There isn’t a region that isn’t already affected by the disease. This rapid decline of the butternut population is so severe that the U.S. Fish and Wildlife Service have listed the species as a species of Federal concern.
In our area the Butternut tree is dying in record numbers. Rarely do I find a live and healthy Butternut in all of my travels. Unlike the Dutch Elm which quickly takes the life of the tree, the Butternut Canker slowly kills the tree over several months to years. Spores of the fungus can be dispersed by rain splashing and air currents. No doubt insects are also transmitters of this deadly fungi. The fungi can survive and reproduce on a dead tree for up to 20 months.
The disease causes dead branches, top dieback, and discolored bark which has an inky black fluid coming from the cracks. Cankers are elongated and sunken and almost always cause death of the branch by cutting off the circulation. Cutting and removing the infected wood will slow the spread of the infection but there are no known cures or control.
Work is now underway to locate healthy stands of Butternuts and graft resistant trees into clone banks to preserve the genetic makeup of this tree. In addition once the physiology of the canker causing fungi is understood there might be a chance to save this tree. But for now we continue to loose another sentinel of our forests just like the American Chestnut and the American Elm. Until next time…