Yes, an ash tree can often be saved from emerald ash borer (EAB), but only if treatment starts before the infestation destroys more than 30 to 50 percent of the canopy. Once decline passes that point, treatment success rates drop sharply and removal becomes the safer, more cost-effective option. Minnesota has confirmed EAB in Hennepin, Anoka, Ramsey, and surrounding counties, and the insect has already killed hundreds of thousands of ash trees statewide since it was first found in St. Paul in 2009.
How Do I Know If My Ash Tree Has Emerald Ash Borer?
The clearest signs of EAB infestation appear in this order: canopy dieback starting at the top and outer branches, D-shaped exit holes about 1/8 inch wide in the bark, S-shaped larval galleries visible when bark is peeled back, vertical bark splitting, and epicormic sprouting, new shoots growing directly from the trunk or root collar as the tree tries to compensate for lost canopy. Increased woodpecker activity is also a strong signal, since woodpeckers strip bark to feed on EAB larvae underneath.
What Is the Treatment Window for Emerald Ash Borer?
The treatment window closes once canopy loss exceeds roughly 30 to 50 percent, according to University of Minnesota Extension guidance. A tree with light to moderate thinning in the upper canopy is still a strong treatment candidate. A tree that has already lost half its canopy or more is generally past the point where insecticide treatment reverses the decline, and continuing to treat it wastes money the homeowner could put toward removal and replacement.
What Treatment Options Actually Work?
Two insecticide approaches dominate EAB treatment in Minnesota, and both require a trained applicator for reliable results.
Trunk Injection (Emamectin Benzoate / TREE-age)
Trunk injection delivers emamectin benzoate directly into the tree’s vascular system, where it is distributed throughout the canopy. This is the most effective treatment available and typically provides two years of protection per application. It requires professional equipment and is the standard recommendation from University of Minnesota Extension and the Minnesota Department of Agriculture for high-value ash trees worth saving.
Soil Drench or Basal Bark Treatment
Lower-cost systemic insecticides applied to the soil or lower trunk offer less reliable, shorter-duration protection than trunk injection. These are sometimes used on smaller ash trees but generally underperform trunk injection on larger, more established trees, which is most of what Dynasty Tree Experts treats across the Twin Cities.
Treatment Cost vs. Removal Cost in Minnesota
| Option | Typical Cost | Frequency | Best For |
|---|---|---|---|
| Trunk injection (TREE-age) | $150-$350 per treatment | Every 2 years | High-value, healthy-canopy ash trees |
| Soil/basal treatment | $75-$150 per treatment | Annually | Smaller ash trees, lower budget |
| Removal (mature ash) | $800-$2,500+ | One-time | Trees past the treatment window |
Over a 10-year span, ongoing trunk injection treatment often costs less in total than a single large removal, which is why Dynasty Tree Experts recommends treating healthy, high-value ash trees rather than waiting for decline to force a removal decision under worse conditions.
Should I Treat or Remove My Ash Tree?
Treat if the tree shows less than 30 percent canopy loss, has significant landscape or shade value, and sits in a low-risk fall zone. Remove if the tree already shows more than 50 percent dieback, has structural decay from woodpecker damage or dead limbs over a roof or driveway, or the property has multiple mature ash trees where treating all of them is not financially realistic. Dynasty Tree Experts assesses every ash tree individually rather than applying a blanket recommendation, since a tree’s location, value, and infestation stage all factor into the right call.
How Do Arborists Confirm an EAB Diagnosis?
A visual inspection catches most cases, but Dynasty Tree Experts also checks for secondary indicators that homeowners often miss: bark that has thinned enough for woodpeckers to strip large patches (“blonding”), suckering at the base of the trunk, and canopy thinning that is asymmetric, meaning one side of the crown declines faster than the other because that side is closer to where beetles first entered. In ambiguous cases, peeling back a small section of bark to look for the S-shaped larval galleries directly confirms an active infestation versus another stress factor like drought or storm damage.
Why Minnesota’s Ash Population Is Especially at Risk
Minneapolis and many inner-ring suburbs planted ash trees heavily as boulevard replacements after Dutch elm disease wiped out the elm canopy in the 1970s and 1980s. That decision created large, even-aged stands of a single species along entire blocks, which is exactly the condition that lets EAB spread fastest once it arrives in a neighborhood. Hennepin County alone has hundreds of thousands of ash trees on public and private property, and University of Minnesota Extension estimates that without treatment, the large majority of untreated ash in an infested area will die within 6 to 10 years of the insect’s arrival.
What Happens If I Do Nothing?
An untreated, infested ash tree does not simply die and stay standing. As EAB galleries girdle the vascular tissue, the wood becomes brittle and structurally unreliable well before the tree is visibly dead, often within 2 to 3 years of initial infestation. Dead ash trees are a leading cause of property damage claims during storms in EAB-affected Twin Cities neighborhoods, because branches and entire trunks fail with little warning. Waiting until the tree is obviously dead to schedule removal usually means paying an emergency removal premium instead of a planned removal rate.
Frequently Asked Questions
How much does emerald ash borer treatment cost in Minnesota?
Trunk injection treatment typically runs $150 to $350 per application and is needed roughly every two years for the life of the tree. Larger, more mature ash trees fall toward the higher end of that range.
Is it too late to save my ash tree if I already see D-shaped exit holes?
Not necessarily. D-shaped exit holes confirm an active infestation but do not by themselves mean the tree is past saving. What matters most is the percentage of canopy already lost, which should be assessed by a professional before deciding to treat or remove.
How long does emerald ash borer treatment last?
Trunk injection with emamectin benzoate typically provides two years of protection per treatment. The tree needs re-treatment on that cycle indefinitely, since EAB pressure in an infested region does not go away.
Does Dynasty Tree Experts treat or only remove ash trees?
Dynasty Tree Experts offers both emerald ash borer treatment and full ash tree removal across Minneapolis, Plymouth, Maple Grove, Brooklyn Park, Anoka, Coon Rapids, and the broader Twin Cities metro, and can assess which option makes sense for your specific tree. Learn more about our tree removal services or contact us for an ash tree assessment.
If you suspect emerald ash borer in an ash tree on your Twin Cities property, do not wait to have it assessed. Schedule an evaluation with Dynasty Tree Experts or call (763) 301-9185 for treatment or removal options.