Walnut Twig Beetle

Walnut twig beetle larvae tunnel inside twigs and branches of walnut trees, girdling shoots and causing dieback. You will notice small, round exit holes in the bark and progressive branch death. This beetle is a vector for the pathogenic fungus that causes thousand cankers disease (TCD), which kills walnut trees. Western Washington walnut plantings are generally at low risk due to cool temperatures.

Prune out infested branches well below visible damage and burn or bury all pruning material to eliminate larvae. Remove heavily infested trees to prevent spread. Do not move walnut logs or wood from affected areas. Since thousand cankers disease is rare in western Washington, no large-scale intervention is currently warranted. Monitor imported walnut stock for beetle or fungal signs.