Emerald Ash Borer in Ottawa in 2026: Should You Treat or Remove Your Ash Tree?

 If you have an ash tree on your Ottawa property, Emerald Ash Borer (EAB) is still a serious concern in 2026. The invasive beetle has already caused extensive damage to Ottawa’s ash population, and the City continues to manage affected trees through treatment, removal, and replacement programs.

For homeowners, the biggest question is no longer simply “Does my ash tree have Emerald Ash Borer?” It is:

“Is my ash tree healthy enough to treat, or has it reached the point where removal is the safer choice?”

The answer depends on the condition of the tree, the severity of the infestation, its location, and the potential risk to your home and property.

What Is Emerald Ash Borer?

Emerald Ash Borer is an invasive beetle that attacks ash trees. The larvae feed beneath the bark and damage the tissues responsible for transporting water and nutrients throughout the tree.

As the infestation progresses, an ash tree can lose canopy density, develop dead branches, and eventually become structurally unsafe.

Ottawa identifies several common signs of EAB infestation, including:

• Thinning or dying foliage
• Yellowing or premature leaf loss
• Dieback in the upper canopy
• New branch growth lower on the trunk
• Increased woodpecker activity
• S-shaped galleries beneath the bark
• Small, D-shaped exit holes in the trunk and branches

However, not every ash tree showing stress should automatically be removed. A professional assessment is important before making that decision.

Why Emerald Ash Borer Is Still a Concern in Ottawa in 2026

EAB is not simply an old Ottawa tree problem that has disappeared.

The City continues to manage ash trees affected by the pest. In 2026, Ottawa planned to treat approximately 600 ash trees within the Greenbelt with TreeAzin® systemic insecticide between May 15 and August 31. Residents can also use GeoOttawa to check whether particular City ash trees are included in the 2026 injection program.

The City’s broader EAB strategy includes a combination of:

• Treating suitable ash trees
• Removing affected trees
• Replanting after removal
• Proactive tree planting
• Public education

This is important for homeowners because treatment and removal are both legitimate management options. The right choice depends on the individual tree.

Should You Treat Your Ash Tree for Emerald Ash Borer?

Treatment may make sense when an ash tree is still relatively healthy and has enough viable canopy and structural condition to justify protecting it.

A professional may consider treatment when:

• The tree has substantial live canopy remaining
• Structural defects are limited
• The tree provides significant shade or landscape value
• The location makes preservation worthwhile
• The infestation has not progressed too far
• The homeowner is prepared for ongoing treatment

The goal of treatment is to protect a viable ash tree rather than wait until it becomes severely weakened.

Ottawa's own EAB strategy includes systemic insecticide treatment for selected trees, demonstrating that preservation can be appropriate for certain ash trees.

Treatment Is Not a One-Time Fix

One important consideration is that treating an ash tree is different from treating a short-term lawn or garden pest.

A tree being treated for EAB needs ongoing professional evaluation and appropriate treatment timing. If the tree has already suffered substantial decline or structural damage, continuing to invest in treatment may not make sense.

That's why an assessment should come before deciding to treat.

When Should an Ash Tree Be Removed?

Removal becomes more appropriate when an ash tree has deteriorated to the point where its structural condition presents an unacceptable risk.

Warning signs can include:

• Extensive canopy dieback
• Large dead branches
• Significant trunk damage
• Severe bark damage
• Structural cracks
• Major decay
• A pronounced lean
• Weak or compromised branch attachments
• The tree is close to a house, garage, driveway, road or other structure

EAB can make an already declining ash tree particularly concerning because dead and weakened wood can become hazardous.

If a tree is already dead or structurally compromised, treatment cannot restore the damaged wood. In those situations, removal may be the responsible option.

Treat or Remove? A Simple Way to Think About Your Ash Tree

Tree Condition	Likely Option
Healthy ash with early EAB symptoms	Professional assessment and possible treatment
Moderate decline but good structure	Assessment to determine whether treatment is worthwhile
Significant canopy loss	Treatment may be less effective; evaluate carefully
Major dead branches and structural problems	Removal may be recommended
Dead ash tree	Removal
Ash tree threatening a structure	Prompt professional assessment

This table is only a starting point. Tree condition can vary considerably, so a certified arborist should make the final recommendation after inspecting the tree.

Why Waiting Can Make Ash Tree Removal More Difficult

One of the biggest mistakes homeowners can make is waiting until an ash tree becomes completely dead before addressing it.

A declining tree can become more difficult and potentially more hazardous to remove as its structural integrity deteriorates.

A large ash tree growing beside a house, fence, garage or utility line requires careful planning and controlled removal.

Early assessment gives homeowners more options.

Instead of waiting for a dead tree to become an emergency, you can determine whether it is worth treating, whether selective pruning can address specific hazards, or whether planned removal is the safer solution.

What About an Ash Tree That Still Looks Healthy?

This is where things can become confusing.

An ash tree may not look severely damaged even when EAB is present. Ottawa notes that symptoms can include changes in canopy density, new growth patterns, woodpecker activity and physical signs beneath or on the bark.

So, don't use the appearance of the leaves alone to decide whether an ash tree is safe or worth treating.

If you have a mature ash tree that you want to preserve, an arborist assessment can help determine its current condition and whether treatment is a reasonable investment.

What Should Ottawa Homeowners Do With a Dead Ash Tree?

If your ash tree has already died from EAB, leaving it standing indefinitely may create unnecessary risk.

Private property owners are responsible for removing and disposing of affected ash trees on their properties, and the City recommends using a Certified Arborist for this work.

Ottawa also has specific rules concerning tree removal. Interestingly, the City's Tree Protection By-law states that private ash trees infested with Emerald Ash Borer can be removed without a permit, although the removed material must be disposed of according to applicable requirements.

Before removing any tree, homeowners should confirm the current requirements that apply to their specific property and situation.

Can You Replace an Ash Tree After Removal?

Yes.

Removing an ash tree doesn't have to mean losing the benefits of having a large tree on your property permanently.

Ottawa has supported ash replacement and broader tree-planting initiatives following EAB-related losses. The City's ash tree replacement program has offered financial assistance for eligible removal and replacement projects, subject to program requirements and available funding.

When replacing an ash tree, the goal should not simply be to plant another tree in exactly the same spot without considering species selection, mature size, soil conditions and available space.

Choosing a suitable, diverse species can help create a more resilient landscape.

Why Professional Assessment Matters

Determining whether to treat or remove an ash tree isn't simply a matter of identifying EAB.

An arborist should consider:

• The amount of live canopy remaining
• Trunk condition
• Branch structure
• Evidence of decay
• Root and soil conditions
• Tree lean
• Nearby buildings and other targets
• Overall site conditions
• The tree's value to the property
• The likely benefits of treatment versus removal

Ottawa recommends that private property owners retain a Certified Arborist when dealing with affected ash tree removal.

For homeowners, this assessment can prevent two expensive mistakes: removing a tree that could have been preserved or keeping a tree that has become a safety hazard.

Don't Wait Until Your Ash Tree Becomes an Emergency

If you have an ash tree on your Ottawa property and you're seeing thinning foliage, dead branches, unusual woodpecker activity, bark damage or other signs of EAB, now is a good time to have it assessed.

A professional assessment can help answer the question that matters most:

Can this ash tree still be protected, or is removal the safer choice?

Green Thumb Tree Specialists provides professional tree assessments and Emerald Ash Borer tree removal in Ottawa. Our ISA-Certified Arborist can evaluate the condition of your ash tree and help you understand whether treatment, pruning or removal makes the most sense for your property.

Need an ash tree assessed? Contact Green Thumb Tree Specialists for a professional evaluation.

Frequently Asked Questions

Can Emerald Ash Borer kill an ash tree?

Yes. EAB damages the tissues beneath the bark that transport water and nutrients, and severe infestations can eventually kill the tree.

Can an ash tree with Emerald Ash Borer be saved?

In some cases, yes. Ottawa's EAB management strategy includes treatment of selected ash trees, so an infestation does not automatically mean immediate removal. The tree's condition and infestation level need to be evaluated first.

How do I know if my ash tree has Emerald Ash Borer?

Look for canopy thinning, dieback, yellowing leaves, increased woodpecker activity, S-shaped galleries beneath the bark and D-shaped exit holes.

Should I remove a dead ash tree in Ottawa?

A dead ash tree should be professionally assessed because it can become a safety hazard, particularly when located near homes, vehicles, walkways or other structures. Private property owners are responsible for removing and disposing of affected ash trees.

Can I remove an EAB-infested ash tree without a permit in Ottawa?

Ottawa's Tree Protection By-law states that private ash trees infested with Emerald Ash Borer can be removed without a permit. Disposal requirements still apply, so homeowners should verify the current City requirements before proceeding.

Should I treat or remove my ash tree?

There is no single answer for every tree. A relatively healthy ash tree may be a candidate for treatment, while a severely declining, dead or structurally unsafe tree may be better removed. A professional arborist assessment is the best way to determine the appropriate option