Thousand Canker Disease

Thousand cankers disease (TCD), recently discovered in Pennsylvania, poses a significant new threat to black walnut. Black walnut (Juglans nigra) wood products have the highest value per board foot of any native tree species in Pennsylvania. Forest inventories show Pennsylvania has over 28 million black walnut trees on forested land. Black walnut has commercial value in numerous forms including veneer, lumber, and nut products. Walnut wood has a long-standing reputation with consumers as being highly desirable for furniture, cabinets, interior trim, wood carvings, musical instruments, and gun stocks. Nuts from walnut are used in many products from foods and flavorings to polishing compound.sf-Geosmithia morbida canker.jpg

Thousand cankers disease is a complex that is caused by a fungus (Geosmithia morbida) that is spread from tree to tree by the walnut twig beetle (Pityophthorus juglandis). Black walnut is highly susceptible to this disease. Adult bark beetles carry fungal spores that are introduced into a tree when the beetles burrow under the bark to construct galleries. Small cankers develop around the galleries; these cankers may enlarge and coalesce to completely girdle a branch. Trees die as a result of these canker infections at each of the thousands of beetle attack sites, usually within 10 years.  There is no known cure for thousand cankers disease. 

The earliest symptom is yellowing foliage that progresses rapidly to brown wilted foliage, then finally branch mortality. The fungus causes distinctive circular to oblong cankers in the phloem under the bark, which eventually kill the cambium. The bark surface may have no symptoms, or a dark amber stain or cracking of the bark may occur directly above a canker. Numerous tiny bark beetle entrance and exit holes are visible on dead and dying branches and bark beetle galleries are often found within the cankers. In the final stages of disease even the main stem has beetle attacks and cankers.

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Download photos of thousand canker disease symptoms.

Visually inspecting walnut trees for dieback is currently the best survey tool for the Eastern United States. Look for declining trees with the symptoms described above. For more information or to report a possible case of thousand cankers disease on walnut please contact your local county office of Penn State Cooperative Extension: or contact the Invasive Species Hotline at 1-866-253-7189 or

Pennsylvania has prepared a Thousand Cankers Disease Action Plan with the broad objective of slowing the spread of TCD. The initial goals are to detect and contain walnut twig beetle and the Geosmithia morbida fungus and then mitigate their impact. The Action Plan will guide a statewide coordinated response amongst key agencies and help local communities respond to the negative effects of the thousand cankers disease.

A new quarantine order was issued on July 22, 2014, to include Bucks, Chester, Delaware, Montgomery and Philadelphia counties.  No walnut material may be moved outward from these five counties. This includes nursery stock, budwood, scionwood, green lumber and stumps, roots or branches living or dead, cut or fallen. No mulch or chips – composted or un-composted may leave the quarantine area. Due to the difficulty in distinguishing between species of hardwood firewood, all hardwood firewood is considered quarantined.

Non-compliance with the quarantine order could result in criminal penalties of up to 90 days imprisonment and a fine of up to $300 per violation, or a civil penalty of up to $20,000 per violation. The quarantine does not prohibit the movement of nuts, nut meats, hulls, processed lumber which is one hundred percent bark-free and kiln-dried with squared edges and finished wood products without bark, including walnut furniture, musical instruments, and other items derived from the genus Juglans.

Download a factsheet and a map of Pennsylvania counties under a quarantine against the movement of walnut materials.
Regulatory questions should be directed to the Pennsylvania State Plant Regulatory Official, Dana Rhodes, in the PA Department of Agriculture, 2301 N. Cameron St., Harrisburg, PA 17110. Phone: 717.772.5205 or email:
For more information visit the Pennsylvania Department of Agriculture's thousand cankers web page