Thousand Cankers Disease offers new threat to Walnut trees

Five years ago a disease was discovered in Ohio that posed a real threat to our Black Walnut population. Since then, scientists have seen a decrease in its host beetle population, but the threat of repopulation remains.

Here are some facts to know about Thousand Cankers Disease (TCD):


  • Discovered in the early 2000s in the western United States, TCD is a fungal disease carried by Walnut Twig Beetles and found in various walnut species,

  • Eventually making its way to Ohio via the transport of unprocessed walnut wood, TCD has proven especially deadly in eastern black walnut trees.

  • Fungus-carrying beetles burrow into the leaf stems of black walnut trees infecting the surrounding phloem tissue – which is responsible for spreading nutrients from leaves to the rest of the tree. The burrows create circular, dark brown ‘cankers’ that eventually kill the tree.


  • Yellow foliage and thinning of the upper crown are the first symptoms.

  • As the disease progresses, multiple areas of dead tissue – or cankers – form underneath the outer bark of branches, stems, twigs, and trunks.

  • As cankers spread, they eventually reach the actively growing layer of tissue, called cambium. These cankers will start to combine with one another, preventing nutrients and water from reaching a tree’s branches.

  • As cankers grow larger and deeper, branches begin to die – eventually killing a tree in as little as three years.

There is no known treatment for TCD so management efforts are focused on prevention and proper disposal of dead or dying trees.

If you are concerned about Black Walnuts on your property, or have other questions about your trees, please contact Ripley Tree Service, an independent family business serving northeast Ohio since 2001.

Image by Whitney Cranshaw, Colorado State University,

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