Thousand Cankers Disease of Walnut
The Kansas Department of Agriculture enacted an exterior quarantine, effective, July 20, 2010, regarding Thousand Cankers Disease of Walnut. Please click below for full text of the quarantine:
A Thousand Cankers Disease of Walnut Quarantine Fact Sheet is available to further explain the details of the quarantine.
The Quarantine also requires individuals or businesses handling “regulated articles” in Kansas to register with the Kansas Department of Agriculture. Those importing such articles must also enter into a compliance agreement. “Regulated articles” include, but are not limited to, logs, lumber, firewood, bark, mulch, burls, stumps, live plants, packing material and all other articles of walnut (genera Juglans). Exempt from the quarantine are nuts, nut meat, hulls, and processed lumber that is bark free and from states where Thousand Cankers Disease of Walnut is not found. If you or your business handles "regulated articles" as defined above, please fill out a Kansas Walnut Registry Application and return it to Kansas Department of Agriculture, Plant Protection and Weed Control.
Current states where Thousand Cankers Disease of Walnut is detected included: Arizona, California, Colorado, Idaho, New Mexico, Tennessee, Oregon, Pennsylvania, Utah, Virginia and Washington.
More information about the Thousand Cankers Disease of Walnut quarantine will be posted as it becomes available.
Thousand Cankers poses a serious threat to the health of black walnut trees. Walnut trees are important because they produce nuts and highly desired wood.
The Kansas Department of Agriculture, Kansas Forest Service and K-State Research and Extension need your help to help stop the introduction, and to limit the spread, of this disease in Kansas. We are deeply concerned that if it reaches the native range of black walnuts in central and eastern Kansas, we may lose this tree in our urban and native forests.
Currently, the disease is known to exist in the nearby states of Colorado and New Mexico. Colorado scientists believe that the disease was brought into its urban areas by moving infected wood either as firewood or for woodworking. Wood, bark, and chips with beetles and cankers are highly contagious and should not be moved off a site for three years. Do not bring in walnut wood from out-of-state sources.
What to Look for in a Tree
Thousand Cankers disease of walnut is a progressive disease that kills a tree within two to three years after initial infection.
The disease causing fungus, Geosmithia sp., is transmitted by a small twig beetle. Branches and trunk tissue are killed by repeated infections by the fungus, as beetles carry the fungus into new bark cambium tissue, repeating the infection. That’s why it is called thousand cankers disease.
Here are several key points to remember when surveying and sampling for thousand cankers. Dead trees require careful scrutiny of the localized area.
- Look for declining trees. Initial symptoms are yellowing and thinning followed by death in two to three years. This is early symptom development.
- Trees with dead leaves are highly suspect and an advanced symptom. Branches collapse in late spring and summer, and leaves die and remain attached to the branch. This flagging symptom is similar to Dutch elm disease.
- In Colorado, twig beetles are attracted to branches with southern and western exposure. Samples should come from this area of the tree, if possible.
- Collect a sample from branches 2 to 4 inches in diameter. Cut the branch down.
What to Look for in a Branch
Take a strong bladed knife or drawknife, and cut or scrape away the bark. Now take the knife and carefully slice the tissue directly under the bark parallel to the surface, peeling away the layers. If dieback is caused by thousand cankers, you will see:
- Black cankers about the size of a dime or larger.
- Beetle galleries in the centers of the cankers.
You may also see:
- Beetles about the size of a pencil lead.
- A gray spot/mass in some beetle galleries. This is a fungus colony.
- Small beetle entry holes in the bark above the cankers.
Twig beetle entry holes.
Photo by M. Kennelly, KSU
For more information, see:
Thousand Cankers Pest Alert