Thousand Cankers Disease

​​​​Thousand cankers disease kills black walnut trees, a high value timber crop. We have not found TCD in Wisconsin, and the Department of Agriculture, Trade and Consumer Protection is trying to keep it out of the state. We have an estimated 19 million black walnut trees, mostly in the southern and western part of Wisconsin, with some pockets in the North Woods.

Scientists believe that a fungus, Geosmithia morbida, causes the disease, and that the fungus is transmitted by a tiny insect called the walnut twig beetle. The beetle burrows into the bark of walnut trees to feed and lay eggs, carrying the fungus with it. When the next generation of beetles emerges from the tree, they carry spores from the fungus to infect another tree when they repeat the life cycle. The walnut twig beetle is native to the Western United States. However, in recent years it has been found east of the Mississippi, although not in Wisconsin.  

What to look for

Quarantine requirements

What to do if you suspect TCD or walnut twig beetle


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