Emerald Ash Borer and Boise Ash Trees: What to Watch For
Quick answer: Emerald ash borer (EAB) is an invasive beetle that kills untreated ash trees. As of April 2026, it had not been detected in Idaho. The nearest Western detections are in Oregon and Colorado. Idaho officials are asking the public to watch for signs and report them. If you have ash trees, learn the signs and talk to a tree care professional about monitoring.
What emerald ash borer does
The larvae feed under the bark and cut off the tree's flow of water and nutrients. Officials note that untreated ash trees are expected to die within a few years of an infestation. The beetle has spread through most of the eastern United States and into southeastern Canada.
Signs to watch for on ash trees
- D-shaped exit holes in the bark, about 1/8 inch across
- S-shaped galleries under loose bark
- Thinning and dieback starting at the top of the crown
- New shoots sprouting from the trunk or base
- Extra woodpecker activity and bark flecking
Other problems can cause some of these symptoms too, so a professional check is worthwhile.
How to report it
Report suspected EAB to the Idaho State Department of Agriculture. Officials also point to the University of Idaho Extension's insect identification resources. Don't move ash firewood; moving wood is a common way pests spread.
Should you treat now?
Because EAB hadn't been detected in Idaho as of April 2026, discuss monitoring and treatment timing with a tree care professional rather than treating straight away, and watch for state announcements.
Sources: Capital Press, 2026-04-14: Idaho officials urge public to watch for emerald ash borer · Idaho State Department of Agriculture: Emerald ash borer · University of Idaho Extension BUL 1077