How to identify an ash tree, recognize common EAB signs and decide between ongoing treatment and timely removal.
| QUICK ANSWER: Emerald ash borer (EAB) is an invasive beetle whose larvae feed beneath ash bark and interrupt the flow of water and nutrients. Untreated ash trees die. Healthy, valuable trees may be candidates for repeated professional insecticide treatment; declining or hazardous trees are usually better candidates for removal. |
Concerned about a private ash tree in Madison or Dane County? Call Vanderbilt Tree Service at 608-351-1134 for an assessment and free written estimate for recommended tree work.
What is emerald ash borer?
Emerald ash borer, or Agrilus planipennis, is a small metallic-green beetle that attacks true ash trees in the Fraxinus genus. Wisconsin first confirmed EAB in 2008, and the pest has since been detected in all 72 counties. The adult beetle is small; most homeowners notice tree damage rather than the insect itself.
First confirm that the tree is an ash
Ash trees can be confused with boxelder, walnut and hickory. Look for several traits together rather than relying on one leaf:
- Branches and buds usually grow opposite each other on the twig.
- Leaves are compound, commonly with 5–11 leaflets along a central stalk.
- Mature bark often develops interlacing, diamond-shaped ridges.
- Seeds, when present, are paddle-shaped samaras that hang in clusters.
| IDENTIFICATION NOTE: A D-shaped hole does not prove the tree is ash. Confirm the species first, then look for multiple EAB signs or ask an arborist to inspect it. |
Signs of emerald ash borer infestation
- Thinning or dieback in the upper canopy, often progressing downward.
- Small D-shaped adult exit holes in the bark, about 1/8 inch wide.
- S-shaped larval galleries visible beneath loose or split bark.
- Heavy woodpecker activity or pale “flecked” patches where bark has been removed.
- Vertical bark splits over feeding galleries.
- Dense shoots or sprouts growing from the trunk or tree base.
EAB symptoms can be difficult to spot early. By the time canopy decline is obvious, the infestation may have been present for years. Avoid peeling bark or climbing a weakened tree to search for holes.
Can an ash tree be saved?
Some ash trees can be protected, but successful treatment is an ongoing commitment. The decision depends on tree health, canopy condition, structural value, location, treatment cost and the cost and risk of eventual removal.
| Consider treatment when… | Consider removal when… | Why timing matters |
| The tree is healthy or only lightly affected, structurally sound, well located and valuable enough to justify repeated professional care. | Canopy loss is advanced, the trunk or major limbs are structurally compromised, the location is poor, or long-term treatment is not practical. | EAB-killed ash becomes brittle. Earlier planned removal is generally safer and may be less complex than waiting until the tree is dead. |
How professional EAB treatment works
Insecticides can protect an ash by killing larvae or adults that feed on the tree. The City of Madison injects selected public ash trees with emamectin benzoate on a multi-year cycle. Product, dose, timing and retreatment interval belong in a professional plan; treatment does not restore dead branches or correct structural defects.
- Treatment is preventive or protective, not a one-time cure for a severely declined tree.
- A healthy canopy and sound structure make a tree a stronger candidate.
- Professional trunk injection limits off-target exposure compared with indiscriminate spraying.
- The owner should compare the lifetime treatment commitment with removal and replacement.
When ash tree removal is the safer choice
Removal is appropriate when the tree is dead, has substantial canopy loss, is shedding limbs, is structurally unsound or cannot reasonably be maintained with ongoing treatment. Dead ash can become brittle and unpredictable, especially near homes, driveways, sidewalks and play areas. Do not attempt to climb or dismantle an EAB-killed ash yourself.
Vanderbilt Tree Service can assess the work area, safely remove hazardous ash trees, complete cleanup and quote stump grinding when removal is the selected plan.
Private ash tree or City of Madison terrace tree?
The responsibility depends on where the tree stands. The City of Madison manages trees in the terrace or public right-of-way and says it treats approximately 10,000 selected ash trees on a multi-year cycle. If the tree is between the sidewalk and street, contact Urban Forestry rather than arranging private work. Owners of private-property ash trees should consult a certified arborist and decide whether to treat or remove.
What should happen to EAB-infested wood?
Use wood locally and follow current Wisconsin firewood rules. EAB larvae live beneath bark and can survive in dead wood for up to two years. Wisconsin DNR recommends buying and using local firewood and notes that firewood brought onto state property is subject to distance and pest-quarantine rules. Do not transport suspect wood simply to get it off the property.
What to do if you suspect EAB
- Keep people away if the tree is dead, dropping limbs or leaning toward a target.
- Confirm that it is an ash using opposite branching, compound leaves and mature bark traits.
- Photograph the canopy, trunk, exit holes, bark splits and any woodpecker activity from the ground.
- Determine whether the tree is private or a City-managed terrace tree.
- Arrange an arborist assessment to compare treatment with removal before decline becomes advanced.
Emerald ash borer FAQs
What should I do if I find emerald ash borer signs?
Confirm the tree is an ash, photograph signs from the ground and arrange an arborist assessment. If the tree is a City of Madison terrace tree, contact Urban Forestry. Keep people away if dead limbs or a new lean create an immediate hazard.
Can an ash tree recover from emerald ash borer?
An untreated infested ash will not recover on its own. A healthy or lightly affected tree may be protected with repeated professional insecticide treatment, but dead branches and structural damage do not regrow.
What is the most effective treatment for emerald ash borer?
Professional systemic insecticides, including trunk-injected products used on an appropriate schedule, can protect suitable ash trees. The best product and interval depend on tree size, health, site and label requirements.
Is emerald ash borer treatment worth it?
It may be worth treating a healthy, structurally sound, valuable and well-placed ash. Compare recurring treatment costs with removal, replacement and the shade or property benefits the tree provides.
Can you burn wood infested with emerald ash borer?
It can be used locally when it is safe and lawful to burn, but do not move it long distances. EAB larvae may survive beneath bark in dead wood for up to two years, and other Wisconsin firewood restrictions can still apply.
How long can an ash tree live with EAB?
Decline varies, but once signs become obvious the tree may already have been infested for years. Untreated ash eventually dies, and advanced decline makes the wood increasingly brittle.
Does homeowners insurance cover an EAB tree?
Policies vary. Insurance generally focuses on sudden covered damage rather than preventive removal of a diseased or infested tree. Ask your insurer about your policy before assuming that treatment or removal is covered.
Get help with an ash tree in Madison
Call 608-351-1134 for a free written estimate. Vanderbilt Tree Service serves Madison and Dane County with certified-arborist-led tree assessment, removal, pruning, stump grinding and 24/7 emergency response.
Sources and further reading
- Wisconsin DNR — Emerald Ash Borer — State status, management and firewood guidance.
- UW–Madison — Emerald Ash Borer in Wisconsin — Identification and homeowner resources.
- UW–Madison — Considerations for Homeowners — Treat, remove or do-nothing decision framework.
- City of Madison — Emerald Ash Borer — Public-tree treatment program and private-tree guidance.