Ash Tree Treatment in Wisconsin
Emerald ash borer has decimated Wisconsin's ash population — but valuable landscape ash trees can still be protected with proper trunk-injection treatment. This guide covers the treatment vs. removal decision, costs, timing, and what we look for during ash assessment in Rock, Dane, Walworth, and Jefferson counties.
Financing available — low monthly payments
Treat It, or Remove It?
The most important decision is whether your ash is healthy enough to be worth treating. Here's the framework.
Treat — Good Candidate
- Less than 30% canopy decline
- Healthy bark with no significant splitting
- Limited woodpecker damage
- Valuable landscape position
- Multiple healthy ash trees on property
Borderline — Assess
- 30-50% canopy decline
- Some bark splitting
- Visible D-shaped exit holes
- Notable woodpecker flecking
- Treatment may extend life 5-10 years
Remove — Beyond Saving
- More than 50% canopy decline
- Dead branches throughout upper canopy
- Extensive bark splitting and falling off
- Major epicormic shoots on trunk
- Structural concerns near targets
Our Treatment Process
On-Site Ash Assessment
An ISA Certified Arborist evaluates each ash tree — canopy condition, bark integrity, woodpecker damage, signs of EAB activity, structural health, and value to the property. We document with photographs and a written tree-by-tree report. No charge for the assessment.
Treatment Plan & Estimate
Based on the assessment, we propose treatment, removal, or a mix. For treatment candidates, we calculate per-tree cost based on diameter and provide a 3-year treatment schedule. You decide which trees to treat — there's no pressure to do all of them.
Trunk Injection (April–June)
We use commercial-grade injection equipment to deliver emamectin benzoate (TREE-äge or Arbor-Mectin) directly into the tree's vascular system through small ports drilled into the trunk base. The pesticide moves systemically through the canopy, killing larvae feeding under the bark. Treatment takes 30-60 minutes per tree.
Follow-Up Monitoring
We track treated trees year-over-year for canopy health and EAB pressure. Treatment intervals are typically 2-3 years; we re-treat on schedule. If a treated tree begins showing decline despite treatment, we reassess — sometimes a borderline tree was past the treatment-feasibility threshold and removal is the right call.
The Real Cost Comparison
Before assuming removal is cheaper, work the math for a typical 24-inch landscape ash tree.
Treatment Path (10-Year View)
- Initial assessment$0
- Trunk injection × 4 (every 2.5 years)$1,200
- Annual canopy inspectionincluded
- 10-year total$1,200
Tree continues to provide shade, property value, and ecosystem benefits. No replacement tree needed.
Remove and Replace
- Tree removal$1,200
- Stump grinding$300
- Replacement tree (3-inch caliper)$600
- Planting and establishment$200
- Year 1 total$2,300
Replacement tree takes 15-20 years to provide similar shade and visual impact. Lost ecosystem value during regrowth period.
For healthy ash trees with significant remaining life, treatment is usually the more economical choice. For declining trees beyond the treatment threshold, removal-and-replace is the right call.
Related Tree Care Guides
EAB in Dane County
Detailed county-specific EAB context for Madison-area properties.
Plant Health Care
Treatment and prevention programs for valuable landscape trees.
Tree Health Assessment
TRAQ-methodology assessment by ISA Certified Arborists.
Tree Removal Services
Removal options for ash trees beyond the treatment threshold.
Oak Tree Care Guide
Care and oak wilt prevention for Wisconsin's heritage oaks.
Maple Tree Pruning
Care for the other dominant Wisconsin shade tree.
Tree Health & Disease Guide
Common Wisconsin tree diseases and treatment options.
Seasonal Care Calendar
Month-by-month care schedule including EAB treatment timing.
Ash Tree Treatment FAQs
Can my ash tree still be saved from emerald ash borer?
Possibly — if it's not too far gone. Trees with less than 30% canopy decline can usually be saved with proper trunk-injection treatment, especially if treatment starts before significant damage. Trees with 30–50% canopy loss may be saveable but recovery is uncertain. Trees with more than 50% canopy decline, dead branches throughout the upper canopy, or extensive bark splitting and woodpecker damage are usually beyond saving and should be removed for safety. Our ISA Certified Arborists can assess your tree and tell you honestly which category it falls into.
What's the best EAB treatment for ash trees in Wisconsin?
Trunk injection of emamectin benzoate (sold as TREE-äge or Arbor-Mectin) every 2 to 3 years is the gold standard for protecting valuable landscape ash trees. Studies in Wisconsin and Michigan show 95%+ effectiveness in preventing EAB damage on healthy or lightly-infested trees. Soil drenches with imidacloprid are an alternative for smaller trees but provide weaker, shorter protection. We use trunk injection on virtually all our EAB protection clients because it's more reliable, longer-lasting, and doesn't expose pollinators to systemic insecticide in flowers.
How much does ash tree treatment cost in Wisconsin?
Trunk injection treatment typically costs $8 to $15 per inch of trunk diameter, every 2 to 3 years. A typical 24-inch ash costs $200 to $360 per treatment, or roughly $80 to $180 per year amortized. Compare that to removal cost ($800 to $2,500+) plus replacement tree cost ($300 to $1,500+ for a decent-sized planting that takes 15+ years to provide similar shade). For valuable landscape ash trees in good condition, treatment is usually the more economical long-term choice. We offer multi-tree property discounts and 3-year treatment programs.
When is the best time of year to treat ash trees?
Mid-April through June is the optimal injection window in Wisconsin — the tree is actively transpiring, which moves the systemic insecticide upward into the canopy where EAB larvae feed. Treatments later in the season (July–August) work but are less consistent. Treatments before bud break (early April) often have poor uptake. We schedule treatment programs starting in mid-April and complete most injection work by late June. Trees in active decline get treatment as soon as practical regardless of season.
Should I treat my ash tree or just remove it?
Decision factors: tree health, location, value, and how long you intend to own the property. Treatment makes sense for healthy ash in prominent landscape positions where you'd miss the shade and visual impact. Removal makes sense for ash trees that are already declining significantly, are in poor structural condition, are in low-value locations (back property line, woods), or where the property owner has short time horizon. Many Wisconsin homeowners with multiple ash trees choose to treat 1 or 2 high-value specimens and remove the rest. Our arborists will give you an honest assessment for each tree.
Is EAB still a problem in Wisconsin in 2026?
Yes. EAB has now been confirmed in nearly every Wisconsin county. The first wave of infestation hit Dane and Rock counties hardest around 2017–2022, when most untreated ash trees died. We're now in the secondary-wave phase where remaining ash trees — both treated and untreated survivors, plus newer plantings — face ongoing EAB pressure. Treatment programs need to continue indefinitely; the borer doesn't go away. Wisconsin DNR and DATCP continue to track EAB statewide.
How do I know if my ash tree is infested with EAB?
Early signs: thinning canopy at the top of the tree, increased woodpecker activity (yellow-bellied sapsuckers and downy woodpeckers feeding on EAB larvae create distinctive flecking on the bark), D-shaped exit holes (about 1/8 inch) on the bark, and serpentine S-shaped galleries visible if the bark cracks or you peel a piece. Advanced signs: dead branches throughout the canopy, epicormic shoots (water sprouts) on the trunk, bark splitting and falling off, and rapid overall decline. By the time you see severe symptoms, the tree is usually beyond saving.
Schedule an Ash Tree Assessment
Get an honest, tree-by-tree evaluation: which ash trees can be saved with treatment, which need to come down, and what each option will cost. Free assessments across Southern Wisconsin.