Walnut Twig Beetle
The walnut twig beetle is the vector that causes the fungus, thousand cankers disease, in walnut trees. It’s a miniscule, brown insect with small hairs covering its body. The fungus they cause is so-named because of the collective impact of multiple cankers: “death by a thousand cuts” becomes death by a thousand cankers.
According to Ohio State University, in some cases, chemical control of walnut twig beetles with insecticide sprays or soil injections may limit the transmission of the fungus to new hosts by preventing initial walnut twig beetle attack. However, the effectiveness of chemical control is limited and only feasible for high value trees. Currently, there are no known fungicides that can be used in the treatment of landscape trees that are effective against thousand cankers disease.
Preventative measures include avoiding moving firewood to different locations, inspecting trees for symptoms of thousand cankers disease and maintaining overall tree health.
Because the walnut twig beetle is directly linked to thousand cankers disease, the effects of the beetle invading an environment will inevitably lead to thousand cankers disease unless action is taken. Originally, it was a concern that the walnut twig beetle would cause a similar situation to emerald ash borers. However, the impact has not followed the devastating trajectory that was expected. While some ecosystems have been affected, the population of walnut twig beetles has decreased over the years.