Bark beetle
Scolytinae
8 host plants
Last updated
Bark beetles bore into stressed or weakened trees, leaving small round entry holes surrounded by frass or pitch tubes on the trunk surface. You will notice fading canopy color, branch dieback, and fine sawdust accumulating at the base of affected conifers. In Western Washington, bark beetle attacks intensify during drought years when trees cannot mount a resin defense against boring adults.
Prevention is the only practical strategy: maintain tree vigor through appropriate watering during drought, avoid soil compaction in the root zone, and promptly remove freshly killed trees before beetles emerge. Chemical bark sprays protect high-value trees preventively but do not cure active infestations. Once beetles establish galleries under the bark, the tree cannot be saved.
Quick Reference
Cultural Controls
- Avoid injury to trees, especially during spring and summer.
- Adult beetles are attracted to wounds.
- On elm, control of bark beetles is essential to prevent the spread of Dutch elm disease.
- Maintain plant health.
- Healthy plants are less susceptible to infestation.
- Select the proper plant for the site and provide proper cultural care.