Photographer: USDA Forest Service – Northeastern Area Source: Bugwood.org Copyright: CC 3.0 US
Ophiognomonia clavigignenti-juglandacearum is a fungus that is specific to the tree butternut (Juglans cinerea). It considered a stem canker, and is able to infect trees through buds, leaf scars, tree openings, and sometimes insect wounds. Butternut canker presents itself as an elongated and sunken canker, with a black, oozing center and white margins.
Butternut wood is highly valued for veneer, cabinetry and carving. However, the ecological impact far outweighs the economic impact. The nuts from butternut trees have become an important crop species, but they are an important food for many forest animals. Their disappearance over the years have severely impacted forest ecosystems. Seedlings, sprouts, and older trees are all vulnerable to this fungus. Unlike other trees susceptible to fungal infections (i.e.: chestnuts), butternut will not grow from the root crown when the top is killed, leading to tree death. Butternut canker can survive on dead trees for up to 2 years, and it is able to kill most trees that it infects. In some states, this fungus has contributed to almost an 80% decrease in butternut trees, and is truly threatening the survival of the species.
Spores that are produced are spread throughout the tree by rain, allowing it to get to other branches. Birds and insects possibly contribute to the spread of this fungus to other trees. The black and white infection sites start entering the deeper layers of the tree, killing the tree cambium, leading to branch dieback.
This fungus was initially detected in Wisconsin in 1967. It is now present in 25 more states, almost across the entire native range of the butternut tree.
U.S. Habitat: Anywhere the butternut trees are present, the tree ranges from eastern Canada to Minnesota and as far south as Alabama, Arkansas, Georgia, Louisiana and Mississippi.
U.S. Present: AL, AZ, CT, DE, IA, IL, IN, KY, MA, MD, ME, MI, MN, MO, MS, NC, NH, NY, OH, PA, RI, SC, TN, VA, VT, WI and WV.
For a county distribution map provided the USDA Forest Service click here.
Quickly recognizing butternut canker is one of the first steps in stopping this troublesome fungus. If you suspect an infestation, quickly contact your state, local or federal entities. Always remember to not move firewood, and burn it where you buy it.
To learn more about the Don’t Move Firewood program click here.
Thankfully, researchers at the USDA Forest Service have a hopeful prognosis on returning butternuts to the eastern landscapes. In natural settings, there seems to be some butternut trees that are resistant to the canker. Those immune trees are being bred, and extensively tested for resistance and conservation by two USDA Forest Service teams.
Broders, K. D., Boraks, A., Sanchez, A. M., & Boland, G. J. (2012). Population structure of the butternut canker fungus, Ophiognomonia clavigignenti‐juglandacearum, in North American forests. Ecology and evolution, 2(9), 2114-2127.
Furnier, G. R., Stolz, A. M., Mustaphi, R. M., & Ostry, M. E. 1999. Genetic evidence that butternut canker was recently introduced into North America. Canadian Journal of Botany, 77(6), 783-785.
Loo, J. A. 2009. Ecological impacts of non-indigenous invasive fungi as forest pathogens. Biological Invasions, 11(1), 81-96.
Michler, C. H., Pijut, P. M., Jacobs, D. F., Meilan, R., Woeste, K. E., & Ostry, M. E. 2006. Improving disease resistance of butternut (Juglans cinerea), a threatened fine hardwood: a case for single-tree selection through genetic improvement and deployment. Tree Physiology, 26(1), 121-128.
Ostry, M. E., & Woeste, K. (2004). Spread of butternut canker in North America, host range, evidence of resistance within butternut populations and conservation genetics. UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE GENERAL TECHNICAL REPORT NC, 243, 114.
Parks, A. M., Jenkins, M. A., Woeste, K. E., & Ostry, M. E. 2013. Conservation status of a threatened tree species: Establishing a baseline for restoration of Juglans cinerea L. in the southern Appalachian Mountains, USA. Natural Areas Journal, 33(4), 413-426.