Walnut Twig Beetle
Pityophthorus juglandis
7 host plants
Last updated
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. Cool-climate walnut plantings are generally at low risk due to temperatures that limit beetle activity.
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. In cool-climate regions where thousand cankers disease is rare, no large-scale intervention is currently warranted. Monitor imported walnut stock for beetle or fungal signs.
Quick Reference
Cultural Controls
- Do not plant susceptible species in areas where TCD is known to occur.
- Maintaining excellent tree health by providing adequate water and good nutrition may help slow progress of the disease, but will not prevent infection or eventual death of infected trees.
- In known TCD areas, do not move live plant material or raw wood (branches, chips, logs, firewood, stumps, etc.) from susceptible trees.
- Beetles are able to complete their lifecycle in cut wood and can also reinfest cut logs that retain any bark.
- Beetles have been observed to survive in large-diameter, freshly cut chips.
- However, chips will dry and become unsuitable host material for both beetles and fungus in a relatively short time, so chipping is considered one of the better ways to deal with infested materials.