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Thousand Cankers Disease Monitoring Project 2022


The Kentucky Division of Forestry is monitoring for the walnut twig beetle, an insect that burrows into black walnut trees leaving them vulnerable to a lethal fungus. Here is what you need to know…

Walnut Twig Beetle | Whitney Cranshaw, Colorado State University,

Background: Thousand Cankers Disease (TCD) is an insect/disease complex caused by the combination of the lethal fungus, Geosmithia morbida, and the walnut twig beetle, Pityophthorus juglandis. This disease is native to the southwestern United States, but in the last decade, TCD has been discovered in many eastern states as well. It has been discovered in several of Kentucky’s neighboring states, however it hasn’t been detected in the Commonwealth to date. Black Walnut is highly susceptible to this disease which causes major dieback and mortality in these trees.

Walnut Twig Beetle damage on a walnut tree | Whitney Cranshaw, Colorado State University,

Signs and Symptoms: The main symptoms of TCD are yellowing foliage and branch dieback. Signs of the fungal pathogen appear as small cankers within the sapwood beneath the bark. Signs of the vector can be hard to observe due to the small size of the beetle. However, evidence of the walnut twig beetle such as tiny burrowing holes and sawdust toothpicks present on the branches can be found on infested trees. Since TCD has not been detected in Kentucky, the KDF Forest Health Program continues to monitor for its presence as it is a severe threat to black walnuts within the state.

Photo of Trap: Deployed in sweetgum tree in Land Between the Lakes.

Monitoring and Trapping: Part of KDF’s monitoring efforts for this disease involves surveying for the insect vector. We accomplish this task by deploying specially designed funnel traps lured for this specific insect. Therefore, if these insects are in your area, we will catch them. These traps will be up from the start of August to mid-October. They will be checked on a bi-weekly schedule. You will notice the traps were not set in walnut trees to avoid bringing the pest to the tree.

Alexandra Blevins, KDF Forest Health Specialist

Thousand Cankers Disease Fact Sheet

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