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Emerald Ash Borer

emerald ash borer

The emerald ash borer (also known as EAB) is a very destructive wood boring beetle which attacks and kills all native species of ash trees.

EAB was first noted in North America in 2002 in Detroit, Michigan and shortly thereafter in Windsor, Ontario. The invasive beetle has since spread to other areas in Ontario, Quebec and the United States.

EAB was first detected in Cornwall and SD&G in June 2013.EAB does not pose a risk to human health.

City of Cornwall Ash Tree Inventory

The City of Cornwall has established an inventory of all ash trees located on City property. 

View the location of these ash trees using the CornwallMaps Interactive Map program.

Click here to open CornwallMaps

Once open, click the 'Custom' tab at the top and select the 'City Ash Trees' layer from the left hand menu.

Movement restrictions, which prohibit the movement of all ash materials - such as logs, branches and wood chips - and all species of firewood from the affected site, have been put in place by the Canadian Food Inspection Agency. Owners of affected properties will be notified of these restrictions.

The City of Cornwall has been preparing for the arrival of the emerald ash borer in the community. Parks and Recreation staff have been monitoring the situation closely while also working to raise awareness about the threat posed by this invasive species.


Management Plan

At the City Council meeting of March 24th, 2014, City Council passed a motion to adopt an "active management" plan to deal with the EAB threat to ash trees on City-owned property, including streets, parks and other public spaces.

Under this management strategy, the City will undertake a more active approach to the EAB infestation by removing dead ash trees, re-planting on a 1:1 ratio with a different specie and adding the pre-emptive removal of ash trees in order to spread the cost of removal over 15 years.

This management plan also introduces the biannual treatment of existing mature ash trees that are in good condition and are greater or equal to 30 cm diameter at breast height (DBH) in order to maintain some of the City's tree canopy until the new plantings are large enough to provide all of the benefits that mature trees provide to the environment. The selected trees are injected with TreeAzin ( azadirachtin) every two years.

Good condition refers to the following criteria:

"Safe useful life expectancy in excess of 20 years, visual importance, forming component part of significant ash species cluster/group/avenue/feature, few adjacent trees, pruning intervention unlikely, few or no above/below ground conflicts, 'heritage' candidate tree, providing significant environmental and other benefits and/or high cost to remove if tree dies."

The cost of implementing this approach if the City decides to treat 100% of the ash trees that meet the "Good condition" criteria is anticipated to be $5.9 million over 15 years. The cost decreases as the percentage of trees selected for treatment decreases. 

This management approach has been recommended by both the City's Municipal Environmental Advisory Committee and the Recreation Advisory Committee. It is based on the Emerald Ash Borer Management Plan that was prepared for the City of Cornwall by Urban Forest Innovations Inc. (the full document is available below).

Additional Information:



Frequently Asked Questions

Here are some answers to commonly-asked questions Don't move firewoodregarding the emerald ash borer:

What does the emerald ash borer look like?
The beetle is green in colour and measures about 3 to 3.5 millimetres wide by 8 to 15 millimetres long.

When present adults might be seen on or near ash trees from early June to the end of August. The adults feed along the margins of ash leaves, they mate, and then the females deposit their eggs in bark crevices or under bark scales.

What tree species are susceptible to attack by the emerald ash borer?
The emerald ash borer has been found to attack and kill all North American species of ash (Fraxinus). The larvae feeds on the cambium layer under the bark which carries water and nutrients.

Infested ash trees typically die two to three years after initial damage is noted.

How important are ash trees?
Ash trees are an important part of Canada's urban and rural landscape. In Cornwall, it's estimated that native ash trees account for 25 to 30 % of all trees within the City.

Like all trees, ash trees help to increase shading and water retention, thereby reducing air conditioning costs and sewage treatment costs. They also help to improve air quality.

How is the emerald ash borer spread?
The most common way for the emerald ash borer to spread is through people moving infested materials such as firewood.

Scientists in Canada and the United States have concluded that the emerald ash borer cannot be eradicated. In light of this the Canadian Food Inspection Agency (CFIA) adopted a "slow-the-spread" approach.

To help limit the spread, ministerial orders have been put in place to regulate areas infested by the pest.

The CFIA is the federal governing body responsible for exotic insects.

What should I do if I have an ash tree on my property?
Property owners are responsible for the care of privately-owned trees. The City of Cornwall recommends you monitor the condition of your tree and look for signs of infestation.

Some signs of infestation include:

  • Presence of woodpeckers in winter and woodpecker holes
  • Thinning crown / dying branches
  • Reduced foliage density
  • Shoots growing from the trunK or branches
  • Deformed bark areas
  • Vertical cracks on the trunk
  • Small D-shaped emergence holes
  • S-shaped tunnels under the bark filled with fine sawdust
  • Evidence of adult feeding on leaves (beginning in late May)

If you see signs that your ash tree is dead or dying, you should contact a professional tree care company.

Also, if you have found a beetle or damage that you suspect is emerald ash borer, contact the Canadian Food Inspection Agency. The CFIA can be reached via email at

Residents who suspect EAB damage are also asked to call the City of Cornwall's Parks and Landscaping office at (613) 930-2787 ext. 2261.

If an emerald ash borer infestation is detected early, you may consider asking your tree care company to assess whether the tree may benefit from injections.

What chemical controls are available?
Currently, three trunk-injectable insecticides are registered for the control of EAB in Canada - TreeAzin (azadirachtin 5%), Confidor 200 SL (imidacloprid 17.1%) and Acephate (ACECAP 97). TreeAzin is the only chemical control treatment that has experienced widespread adoption by municipal programs and private tree care companies for the control of EAB infestation.

What will happen to the City-owned ash tree on or near my property?
City staff require your assistance to monitor the health of City trees in your neighbourhood. If a City tree appears to be in decline, please advise the Parks and Landscaping Section at (613) 930-2787 ext. 2261. The tree will be assessed by a certified arborist and appropriate best arboricultural practices will be applied to maintain the urban forest.


Additional Information

You can find out more about the emerald ash borer through the following resources: