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Invasive Species: Thousand Cankers Disease

Thousand Cankers Disease

(Pityophthorus juglandis + Geosmithia morbida)
*Not detected in Michigan*


Report suspect thousand cankers disease in Michigan:

If black walnut trees have wilting leaves or dying branches during the summer, check the tree carefully. If there is no obvious cause of the problem, such as a broken branch, note the location of the suspect tree and report it. Identifying the tiny walnut twig beetles and confirming the presence of TCD requires specialized expertise.


Phone: MDARD Customer Service Center 800-292-3939

If possible, please take one or more photos of the invasive species you are reporting. Also make note of the location, date and time of the observation. This will aid in verification of your report. You may be asked to provide your name and contact information if follow-up is needed.

- Or - Use the Midwest Invasive Species Information Network (MISIN) online reporting tool

- Or - download the MISIN smartphone app and report from your phone -


TCD beetles on penny
Tiny adult walnut twig beetles. Photo courtesy of Whitney Cranshaw, Col State University.

thousand cankers beetles
Cankers on walnut stem. Photo courtesy of Whitney Cranshaw, CSU, 

thousand cankers diseased tree
Thousand cankers disease tree death. Photo courtesy of Whitney Cranshaw, CSU,

twig beetles exit holes
TCD beetle exit holes. Photo courtesy of Whitney Cranshaw, CSU,

Why we care: Thousand cankers disease (TCD) involves an insect native to the southwestern U.S. and a newly identified pathogen. It is a relatively new concern for black walnut trees. When tiny walnut twig beetles feed on tree branches, they introduce a fungal pathogen that causes TCD in live trees. The pathogen kills small areas of tissue, resulting in cankers. As more cankers form, branches die and over time, the entire tree succumbs.

What is at risk? Michigan's forests are home to approximately 8.5 million black walnut trees with an economic value of more the $86 million and ecological value as a food source for birds, mammals and other wildlife. There are also more than 80 walnut growers in Michigan with approximately 4,000 trees in nut production.

The threat: Black walnut trees in many western states, and in Tennessee and Pennsylvania, are dying from TCD. The beetle and fungus can be transported into new areas in walnut logs, firewood and staves used for woodworking. Black walnut is a valuable timber species and important for wildlife.

What could happen in Michigan? An effective control for TCD has not been identified. A high proportion of black walnut trees will likely die if TCD becomes established in Michigan.

More Information

How to Identify Thousand Cankers Disease and Black Walnut

Quarantine Information

Links of Interest