What Is This Disease?
Thousand Cankers Disease (TCD) primarily attacks black walnut trees (Juglans nigra). It is caused by the combined activity of the Walnut Twig Beetle and a fungus it transmits. The fungus is spread as adult Beetles feed beneath the bark. As the fungus spreads, it kills areas underneath the bark (called cankers), blocking the flow of water and nutrients, often killing the tree. The danger to other species of walnut is still being evaluated.
Signs Of Infestation
TCD is difficult to diagnose and no effective control measures have been developed. Usually, the first symptoms noticed are yellowing, wilting leaves and dead limbs in the upper part of the tree. Dead leaves remain attached to the stems. Closer inspection may reveal small, sometimes weeping Walnut Twig Beetle entry holes in the trunk, or discolored cankers beneath the bark. Infected trees also often produce many suckers from the lower trunk.
Black Walnut Trees Are In Danger
TCD poses a serious threat to an important eastern native tree, which has also been widely planted in the West. Millions of black walnut trees in forests and urban areas are at risk. This tree has great economic and ecological value throughout its native range. Black walnut is highly valued for its beautiful wood used to make furniture and its edible nuts.
Where Is TCD Found?
The Walnut Twig Beetle is native to the western United States. The origin of the disease is unknown. TCD has killed many walnut trees in Arizona, California, Colorado, Idaho, New Mexico, Nevada, Oregon, Utah and Washington. It has also moved east into native ranges of the black walnut and been confirmed in Indiana, Ohio, Pennsylvania, Virginia, North Carolina and Tennessee. Quarantines are in place in those states and many others in the Midwest and Northeast. For a map, see http://www.thousandcankers.com/.
You Can Help Stop The Spread
If you suspect your walnut tree has TCD, contact your state Department of Forestry, Agricultural Commissioner’s office or your local Cooperative Extension System office.
To prevent further spread of TCD, it is very important not to remove wood of infected trees from your property. For information how to properly dispose of infected wood, go to http://www.thousandcankers.com/.
Thousandcanker.com is great resource for information on TCD, including specifics on state quarantines, who to contact if you suspect the disease, and how to dispose of dead trees.
Photo Credit: Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org