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Over the Garden Fence

Where gardeners come to find out what's happening out in the yard.

Thousand Cankers Disease of Walnut

Posted by Sarah Navrotski -

Down the Garden Path

Richard Hentschel, Extension Educator

The past year there has been quit a buzz among plant pathologists and entomologists about the national spread of yet another potentially devastating tree disease in the United States.

Thousand Cankers Disease (TCD) has been declared to be a viable threat to walnut trees in Illinois, so much so that in early February, Governor Quinn approved regulatory measures to monitor and restrict the movement of walnut wood that could be carriers of TCD. Like the Pine wilt nematode is being spread by the Sawyer beetle and Dutch elm disease being carried by the Elm bark beetle, TCD is spread by another insect, the Walnut Twig Beetle.

The disease itself is a fungus that is spread as the Walnut Twig Beetle is feeding just under the bark in the phloem cells. As the fungus grows under the bark, the cells die forming a cancer that leads to decline and eventual death of the Walnut. There will eventually be "thousands" of these cancers in the tree.

Right now this disease has not been detected in Illinois, yet as history would show, we seem to be adept at unknowingly transporting insects and diseases. A most recent example is the Emerald Ash Borer. The regulations are being put in place to prevent the disease or insect from entering Illinois. Similar to the restrictions placed on those dealing with ash wood and products made from Ash, those individuals and companies dealing with walnut lumber and products made with walnut must follow and comply with very specific guidelines that would allow walnut into Illinois. Walnut nuts, Kiln dried lumber without any bark attached would be allowed. There are more products allowed, depending on the product using walnut. If you are a wood worker, any walnut that your hardwood supplier or you have in stock should be fine if it has been in your or their possession for some time. Master Gardeners will have information about TCD available during the growing season. If you are concerned that your walnuts may be infected in the future, the Illinois Department of Agriculture will be the official organization.

For more information regarding TCD, visit the Illinois Department of Agriculture website at and click on the Thousand Cankers Link on the right or click on this direct link.  Thousand Canker Disease and Walnut Tree Beetle

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