Emerald Ash Borer in Montreal: What Homeowners Need to Know

The emerald ash borer (Agrilus planipennis) has been killing ash trees across Montreal for over a decade. The City of Montreal has treated nearly 50,000 public ash trees with insecticide injections and keeps removing dead and dying specimens, but the beetle has permanently changed the urban forest (Source: Ville de Montreal).

If you own property with ash trees, this covers how to identify the pest, what your options are, and how losing an ash tree affects your landscaping.

What is the emerald ash borer

The emerald ash borer (EAB) is an invasive beetle native to Asia. Adults are metallic green, about half an inch long, and narrow. The larvae bore into the bark of ash trees and feed on the inner bark (cambium layer), disrupting the tree's ability to transport water and nutrients. An untreated ash tree typically dies within 3 to 5 years of initial infestation.

EAB was first detected in Canada in 2002 in Windsor, Ontario, and has since spread across Quebec. All species of ash trees native to Quebec (white ash, green ash, black ash, and red ash) are susceptible.

How to identify ash trees on your property

Before worrying about EAB, confirm whether you actually have ash trees. Ash trees have these identifying features:

• Compound leaves: Each leaf consists of 5 to 9 leaflets arranged in opposite pairs along a central stem, with one leaflet at the tip.
• Opposite branching: Branches grow in pairs directly across from each other on the trunk. This is a key identifier, as most common Montreal trees (maples being the notable exception) have alternate branching.
• Diamond-pattern bark: Mature ash trees develop a distinctive diamond-shaped bark pattern with interlocking ridges.
• Seeds: Ash seeds (called samaras or "keys") are single-winged and hang in clusters.

If you're not sure, a certified arborist can confirm the species.

Signs of EAB infestation

Early signs

• Canopy thinning. The upper crown of the tree starts losing leaves before the lower branches. This is because the larvae girdle the upper trunk first, cutting off water flow to the top.
• Increased woodpecker activity. Woodpeckers feed on EAB larvae. If woodpeckers are suddenly paying heavy attention to your ash tree, inspect further.
• Epicormic shoots. New sprouts emerging from the trunk or large branches below the canopy line. This is the tree's stress response, trying to produce leaves below the point where the larvae have cut off nutrient flow.

Advanced signs

• D-shaped exit holes. When adult beetles emerge from the bark, they leave distinctive D-shaped holes roughly 3 to 4 millimeters wide. These are different from the round holes left by other wood-boring insects.
• S-shaped larval galleries. Removing a small section of bark reveals S-shaped tunnels packed with sawdust-like frass (larval waste). These galleries are carved by the feeding larvae just beneath the bark surface.
• Bark splitting. Vertical cracks in the bark caused by the tree's callus tissue growing over larval galleries.
• Significant dieback. More than 30% to 50% of the canopy is dead.

Treatment options for homeowners

Insecticide injection (TreeAzin)

The City of Montreal treats public ash trees with azadirachtin-based insecticide (TreeAzin), a product with low environmental toxicity derived from neem tree seeds. This treatment is administered by injection directly into the trunk, and it must be repeated every two years during the active season (June through August) (Source: Ville de Montreal).

Private property owners can hire a certified arborist to administer the same treatment. The cost varies by tree size but typically ranges from $150 to $400 per treatment for a medium-sized ash.

Important: Treatment is only effective on trees that still have at least 50% to 60% of their canopy intact. Once dieback exceeds that threshold, the tree is unlikely to recover regardless of treatment.

When treatment is not worth it

Treatment may not be justified when:

• The tree has already lost more than half its canopy
• The trunk shows extensive bark splitting and D-shaped exit holes
• The tree is in poor overall health (root damage, structural defects, other diseases)
• The tree poses a safety risk to structures or people

In these cases, removal is the practical choice.

Tree removal and replacement

Permits

Montreal requires a permit to remove trees in most boroughs. The process and fees vary by borough, but generally you must demonstrate that the tree is dead, dying, or poses a safety hazard. Some boroughs require a certified arborist's report confirming the need for removal.

Removal costs

Ash tree removal costs depend on size, location, and access. A medium-sized ash (30 to 50 feet tall) in a typical Montreal backyard with reasonable access typically costs $800 to $2,500 for removal and stump grinding.

Replacement planting

Many boroughs require a replacement tree when a mature tree is removed. Montreal's urban forest now includes 178 different tree species and varieties adapted to local conditions, a deliberate diversification effort to prevent future single-species catastrophes.

Good replacement options for ash include:

• Hackberry (Celtis occidentalis): Tolerates urban conditions, similar size and shape to ash.
• Kentucky coffeetree (Gymnocladus dioicus): Drought-tolerant, pest-resistant, adapted to Zone 5.
• Red oak (Quercus rubra): Long-lived native tree with excellent fall color.
• Ironwood (Ostrya virginiana): Smaller, understory tree for properties where a large tree is not appropriate.

Biological control efforts

Montreal has participated in biological control research since 2015, releasing tiny parasitoid wasps that attack EAB at specific life stages. These natural enemies have been tested at the Jardin Botanique, parc-nature Bois-de-Liesse, and Mont-Royal. Results show the wasps have successfully established and are naturally dispersing into surrounding areas (Source: Ville de Montreal).

Researchers have also tested fungal-based traps that infect adult beetles with naturally occurring fungal spores, though this approach hasn't been licensed in Canada for widespread use yet.

These biological controls won't wipe out EAB, but they help knock down population levels and slow the rate of tree death.

Federal regulatory changes

The Canadian Food Inspection Agency (CFIA) conducted a consultation on emerald ash borer management from September to November 2025, with a final decision expected in early 2026. Any resulting changes to regulated areas and movement restrictions could affect how ash wood and nursery stock are transported in and out of the Montreal region (Source: CFIA).

How EAB affects your landscaping plans

Losing a mature ash tree changes a property in ways you might not expect. A large ash provided shade, privacy screening, and a visual anchor for the landscape. When it comes down, you may need to:

• Reconsider sun exposure. Areas that were shaded may now get full sun, requiring changes to shade-loving plantings.
• Replace the privacy screen. If the ash blocked sightlines, you may need a fence, hedge, or fast-growing replacement tree.
• Stump and root management. Grinding the stump leaves a depression that must be filled with soil and reseeded or replanted.
• Adjust drainage. Mature trees absorb significant amounts of water. Without the tree, surface runoff and soil moisture patterns change.
• Redesign the landscape. Without the tree, you can rethink the space entirely: a patio, new planting beds, or a different tree species.

Planning around EAB

If you have ash trees on your property, include them in your landscaping plan. Decide now whether to invest in treatment or plan for eventual removal and replacement. Waiting until the tree is dead creates an emergency removal that costs more and disrupts more than planned removal would have.

Montreal Paysagement Pro works with homeowners on landscape planning that accounts for tree loss and replacement. Call 514-900-3867 for an estimate by phone, photo, or video.