(Sirococcus clavigignenti-juglandacearum)

Photo 35: Archive, Minnesota Department of Natural Resources, Bugwood.org

Biology

• a fungus disease that infects and kills Butternut trees (Juglans cinerea)
• the disease enters a wound and kills inner bark on branches generally in the lower canopy
• gradually, the fungus kills the upper canopy and spreads down the tree to attack trunk tissue
• when the fungus has girdled the trunk, the tree dies
• the disease is probably from outside North America
• the fungus kills mature trees as well as saplings and seedlings
• on branches, the cankers appear as white patches with a black centre
• on the trunk, the fungus causes deep grooves and gashes in the bark that often ooze a black jelly-like material containing the spores of the fungus
• the spores may be spread by rain and insects

Photo 36: Joseph O'Brien, USDA Forest Service, Bugwood.org

History in Canada

• the Butternut tree occurs in southern Ontario, southern Quebec, and New Brunswick
• the canker was first documented in the US in 1967 but it may have arrived there before 1940
• the disease reached Canada in 1990
• the disease has been documented across the entire range of Butternut in Canada

Impact on Trees

• the Butternut tree is an important forest species that provides valuable wood for furniture and nut crops that are used by wildlife and were important to early settlers
• no tree strains are known to have resistance to the disease
• in the southern US, over 75% of Butternut trees have been killed by the canker
• when the trunk is killed, Butternut will not resprout from the base
• Butternut is now considered Endangered in Canada due to the impact and potential impact of the disease

Control

• there is no known cure for trees infected with the canker
• studies are underway across the range of Butternut to locate disease-resistant trees

Links

• Field Guide to Tree Diseases of Ontario. Butternut Canker. Natural Resources Canada. (http://cfs.nrcan.gc.ca/subsite/glfc-treedisease/butternut-canker)
• Global Invasive Species Initiative. The Nature Conservancy. (http://tncweeds.ucdavis.edu/products/gallery/sircl1.html)
• How to Identify Butternut Canker and Manage Butternut Trees. United States Department of Agriculture. (http://www.na.fs.fed.us/spfo/pubs/howtos/ht_but/ht_but.htm)
• Forest Gene Conservation Association. Species at Risk, Butternut. (http://www.fgca.net/conservation/sar/butternut_canker.aspx)
• Three American Tragedies: Chestnut Blight, Butternut Canker, and Dutch Elm Disease. Scott E. Schlarbaum, Frederick Hebard, Pauline C. Spaine, and Joseph C. Kamalay. Report available at: (http://www.srs.fs.usda.gov/pubs/ja/ja_schlarbaum002.htm)