Property, Gardens & Trees

Emerald Ash Borer

The Emerald Ash Borer is a highly destructive invasive beetle that infests ash trees. It has killed millions of ash trees in North America and poses a major environmental threat to urban and forested areas in Hamilton. It has the potential to destroy Hamilton’s entire Ash tree population by the year 2020.

Ash trees are an important part of Hamilton's urban and rural landscape. They are commonly found on city streets, woodlots, windbreaks and forests.

How Emerald Ash Borers spread

The Emerald Ash Borer spreads naturally through beetle flight; the beetle is capable of flying distances of 5 km in search of a host tree. The Emerald Ash Borer is also spread by people moving material infested with the beetle such as firewood and nursery stock. The Canadian Food Inspection Agency regulates the movement of material outside the quarantined area. 

View the Emerald Ash Borer regulated areas of Canada

Identifying Ash Trees

Mountain Ash is not in the same family and is not affected by the Emerald Ash Borer. An Ash tree typically has:

Ash BarkRidged Bark
On mature trees (left), bark is tight and displays patterns of diamond shaped ridges. On young trees (right), bark is relatively smooth.

Image of Ash tree with opposite leavesCompound ‘Opposite’ Leaves
Leaves contain 5 to 11 leaflets with smooth or toothed margins (tips). Leaflets are positioned opposite with one at the top.

Image of Ash tree with hanging seedsSeeds
When present, seeds usually hang in clusters and are dry and oar-shaped.

Image of Ash tree with opposite branches‘Opposite’ Branches
Branches and buds are directly across from each other rather than staggered. However, due to the death and grooming of individual branches, it is possible that not every branch will be opposite.

Identifying Signs of Infestation

Emerald Ash Borer larvae feed underneath the bark and block nutrients and water from moving throughout the tree. The tree may be dead within a few years of the initial infestation. Infested ash trees often exhibit the following symptoms:

Image of Ash tree with Ashe Borer symptoms of crown dieback

Crown Dieback
Severely attacked trees may exhibit crown dieback as the canopy dies from the top down. Leaves may wilt or turn yellow during the growing season.

Image of Ash tree with Ashe Borer symptoms of cracked bark

Bark Cracks
Vertical splits of 7 - 10 cm are often present over larval galleries. These are often more noticeable on young trees that do not already have splits from growth-related expansion.

Image of Ash tree with Ashe Borer symptoms of woodpeckers

Woodpeckers feed on the larvae under the bark. Look for increased Woodpecker feedings or signs of their probing in the bark.

Image of Ash tree with Ashe Borer symptoms of borer exit holes

Exit Holes
Once fully mature, the adult beetles emerge through exit holes they chew through the bark. These holes are distinctly D-shaped and are 3.5 to 4 mm across.

Image of Ash tree with Ashe Borer symptoms of tunneling

Winding S-shaped larval tunnels snake under the bark where larvae bore channels. Removing the bark exposes larvae and sawdust-filled galleries.

Removal of infected trees

Who is responsible for removal of infected trees depends on where the tree is located on your property:

The City will remove an infested ash tree from your property if it is located within the road allowance. If the tree in your front yard is showing signs of being infested with the emerald ash borer, call 905-546- 2489 to have your tree assessed. The City will plant a replacement tree once the infested tree and stump is removed.

You are responsible for all trees that are not on the City’s road allowance. This includes the treatment, removal and disposal of dying or dead Ash trees. Contact an arborist to discuss your options.

If you elect to have your tree removed, ensure that the materials are not moved outside the CFIA quarantined area. The wood and mulch can be utilized for firewood and landscape use within this area.

Contact the Canadian Food Inspection Agency at 1-866-463-6017 or Phytosanitary Requirements to Prevent the Introduction Into and Spread Within Canada of the Emerald Ash Borer for further information.

City Ash trees

In 2012 City Council approved the plan which included the removal of 10% of Hamilton’s Ash tree population each year for a 10 year period. At the current decline rate, it is anticipated the Ash population may be removed in the next four years. Each Ash tree that is removed is replaced with a new species of tree to help diversify Hamilton's urban forest. More information on the Street Tree Planting Program.

The City has also been using injectable pesticide on healthy Ash trees of significance. These trees are treated annually during periods of heavy infestation then subsequently every two years. Treating all City-owned Ash trees is not economically feasible.