Emerald Ash Borer

What is the emerald ash borer?


Emerald ash borer

The emerald ash borer is an invasive exotic insect that attacks ash trees. Since it was detected in Michigan in 2002, it has decimated tens of millions of ash trees in North America.

The small narrow elongated metallic green insect is between 7.5 and 15 mm long and approximately 3 mm wide.

How does the emerald ash borer spread?

The adult beetles generally emerge in May, and infest the tree in which they were living or a nearby ash. Under normal circumstances, the emerald ash borer spreads slowly. However, transporting infested materials, such as recently cut ash wood or firewood from any type of tree, poses the greatest risk of spreading the insect to other regions.

What does an ash tree look like?

The branches and leaves of ash trees grow directly across from each other. The leaves are 5 to 15 cm long, and are composed of 5 to 11 leaflets. The margins of these leaflets may be smooth or toothed.

In the fall, the leaves generally turn yellow, and are among the first to change colours.

The bark has a disctinct pattern of hard ridges that criss-cross in a diamond shape (white ash and red ash), or soft cork-textured ridges that become scaly with age (black ash). Normally, ash trees grow to 15 or 20 metres in height and are of variable shapes.


Healthy ash tree

Ash leaf

Ash fruits: samara

Signs of infestation

Once an ash tree has been infested, the larvae feed under its bark by digging serpentine galleries that end up blocking the movement of water and nutrients in the tree.

The following are signs of infestation:


Thinning of the foliage

Dieback of the crown

Proliferation of sprouts (new shoots on the trunk)

Serpentine (S-shaped) galleries under the bark

Small D-shaped exit holes
Woodpecker feeding holes

Preventing infestation

Ash trees can only be conserved through preventive treatment or controls in the early stages of infestation using a systemic pesticide. Such treatment will not eradicate the emerald ash borer.

The treatment must be repeated at most every two years over a span of 10 to 15 years. It must be done by a specialist.

An ash tree that has not been infested but is not treated will become infested, so it is important to act right away. If in doubt, consult a specialist.

What you should do if your ash tree is infested

Once an ash tree shows clear signs of infestation, it has been infested for at least one year. An infested ash tree that is not treated will die within a few years. Thus it is important to plan for its removal if no treatment will be applied. Cutting an ash tree at the very beginning of its infestation will cost less than waiting until after it dies.

It is a good idea to consult a specialist in order to determine how far the infestation has spread and the appropriate strategy.

Cutting down ash trees

A heavily infested ash tree will not survive the damage caused by the insect, so it should be cut down.

Property owners are responsible for maintaining and cutting down ash trees on their property. If necessary, they are also responsible for replacing those trees.

If you have to cut down an ash tree, it is recommended that you do so between October and March, because the emerald ash borer is not likely to spread to other trees when you cut it down and transport the wood.

Before you cut down an ash tree on your property because it is infested, you will need an authorization certificate from Ville de Gatineau. You can apply for one by calling 3-1-1. This certificate is required to cut down any tree with a diameter greater than 10 cm.

For additional information about protecting trees, consult the page Protecting trees.

Disposing of ash wood

In order to avoid spreading the emerald ash borer, ash tree branches should not be placed with regular household garbage, as can be done with other species.

  • Tree branches and twigs measuring less than 12 mm in diameter and 1.5 m in length can be placed with compostables for collection. 
  • Trunks, stumps and branches measuring more than 12 mm should be brought to the ecocentres or to the waste transfer station.

For all other information about the disposal of ash wood, call 3-1-1.

Prohibition against the transportation of wood

In 2012, the Canadian Food Inspection Agency (CFIA) published a Ministerial Order applicable throughout Gatineau prohibiting the transportation of firewood and ash products outside this regulated area.

Regulated products include ash nursery stock, trees, logs, lumber, packaging and palettes, bark, wood chips and bark chips from the Fraxinus species (commonly called ash). Firewood from trees of any species is also regulated.

These regulated products cannot be moved outside the quarantine area, which includes all of Gatineau, as well as Ottawa, MRC Papineau, MRC des Collines-de-l'Outaouais, the United Counties of Leeds and Grenville, Frontenac and the United Counties of Prescott and Russell (view map).

Failure to comply with these restrictions can result in a fine or legal action.

Municipal action plan

Since 2009, Gatineau has set in place different measures to control the spread of the emerald ash borer and to comply with the CFIA's Ministerial Order, in particular:

  • providing information about the emerald ash borer to residents;
  • preparing an inventory of ash trees throughout municipal lands, and screening for the presence of the insects;
  • training in screening for employees working in parks and other green areas;
  • setting up a site in 2010 for the treatment of ash wood; and
  • introducing a program of treatment with the TreeAzin™ organic insecticide, which has been used on more 1,000 ash trees.

Over the next few years, several ash trees will probably be cut down because of the infestation. Ash trees that are cut down along major roads and in parks will be replaced by new trees.

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