Thousand Cankers disease major threat to black walnut trees

Tiny holes in this black walnut tree are really the exit holes of the walnut beetle, the culprit behind Thousand Cankers disease that will eventually kill a black walnut tree.

LANSING, Mich. — Michigan landowners and consumers are being warned to be on the lookout for scam artists looking to buy black walnut trees using the detection of an invasive species as the hook.

There are reports of log buyers pressuring Michigan woodlot owners and others to sell their black walnut telling them that Thousand Cankers Disease has been detected in Michigan — when it has not been detected in Michigan.

The Michigan departments of Agriculture and Rural Development and Natural Resources continue to have a disease surveillance program in place to look for it.

Found in Ohio, Pa.

Walnut twig beetles were found in Butler County, Ohio, in late 2012, and the presence of Thousand Cankers Disease has since been confirmed in Ohio. The Pennsylvania Department of Agriculture confirmed the presence of Thousand Cankers Disease in Pennsylvania on Aug. 9, 2011.

Although Thousand Cankers Disease does present a real threat to black walnut, to date it hasn’t rapidly spread and impacted walnut on a large scale. It is nothing like an Emerald Ash Borer or Dutch Elm Disease.

If TCD is detected in Michigan, it would be announced by the state identifying the affected areas, outlining the response plan and quarantine restrictions would apply to the affected area. This is often only a small portion of one county.

What is it?

Thousand Cankers Disease is caused by a combination of small beetles boring into walnut branches, and a fungus introduced by the beetles.

The crowns of affected trees begin dying and the tree eventually succumbs.

Black walnut trees in many western states, and in Tennessee and Pennsylvania, are already being negatively impacted by TCD. The beetle and fungus can be transported into new areas in walnut logs, firewood and staves used for woodworking.

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.

Other species quarantined

In May 2010, MDARD established a quarantine to protect Michigan walnut (Juglans spp.) from thousand cankers disease. Michigan’s quarantine restricts movement of the following from infected states into Michigan:

All plants and plant parts of the genus Juglans, including but not limited to: nursery stock, budwood, scionwood, green lumber; other living, dead, cut or fallen wood, including logs, stumps, roots and branches; and composted and noncomposted chips; hardwood firewood; and any article, product or means of transport that risk the spread of the walnut twig beetle or fungus.

Articles that are not a threat and are exempt from the quarantine include:

  • Nuts, nut meats and hulls;
  • Processed lumber that is 100 percent bark-free and kiln-dried with squared edges;
  • Finished wood products without bark.

Valuable crop

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.


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