Emerald Ash Borer

The Emerald Ash Borer beetle is a non-native invasive insect that attacks and kills most varieties of ash trees.

Adult EAB beetles lay their eggs on ash trees in the summer. When the eggs hatch into larvae, they tunnel under the tree's bark to feed. The tunnels prevent the flow of water and nutrients, causing the tree to die. As larvae, they are located between the bark and sap wood. As adults, EABs eat ash tree leaves. Both of these actions, including the fact that EABs do not have any natural predators, lead to infestation and eventual death of the tree (in approximately 1 to 4 years).

In order to deal with the threat posed by EAB, the City of Cornwall's EAB management plan (see below) involves a combination of monitoring, treatment, ash tree removal and replacement, and public education.

Tree removal: Ash trees in the community that have been marked with an orange line on the trunk and an information sign posted on the tree will be removed. When the tree is removed, all limbs will be chipped and wood will be removed off site. The stump will be removed at a future date and if space permits, a new tree will be planted.

Tree injection: Ash trees in the community that have been marked with a green dot at the base of the trunk are candidates to be treated with TreeAzin to protect it against the EAB. TreeAzin is a systemic insecticide injected into the tree's bark to kill EAB larvae feeding on the tree's tissues. It does not pose any health risk to people, pets or wildlife and degrades naturally. It is injected in the tree every year for 2 years than skip a year, then injections for the next 2 years. This is the latest updated change for injections.

Please click here to see the Ash Tree Removal Notice.

Please click here to see the City of Cornwall Tree Planting List.

Please click here to see the March 24, 2014 Report to Council.

Please click here to see the Emerald Ash Borer Management Plan.

Emerald Ash Borer Frequently Asked Questions

What is the Emerald Ash Borer (EAB)?

The EAB beetle is a non-native invasive insect, that attacks and kills most varieties of ash trees (white and green ash). Adult EAB beetles lay their eggs on ash trees in the summer. When the eggs hatch into larvae, they tunnel under the tree's bark to feed. The tunnels prevent the flow of water and nutrients, causing the tree to die.

Where did EAB come from?

The EAB beetle originated in Asia, and is believed to have come to North America in the early 1990's, via the transportation of ash wood materials. It was first detected in Canada in 2002 in Windsor, Ontario. It has since killed and infested over 70 million ash trees.

How does EAB spread?

The most common way for the emerald ash borer to spread is through people moving infested materials such as firewood. To prevent the spread of EAB, don't move firewood, and buy wood locally. 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.

How does EAB impact ash trees?

EAB kills ash trees by eating their nutrients. As larvae, they are located between the bark and sap wood and eat the trees nutrients. As adults, EABs eat ash tree leaves. Both of these actions, including the fact that EABs do not have any natural predators lead to infestation and eventual death of the tree (approx. 1 to 4 years).

What has EAB been found?

EAB has been confirmed through out the City of Cornwall. However, EAB beetles can fly long distances up to 8 km.

Possible signs of EAB infestation

There are a number of possible signs that could indicate a possible EAB infestation.

Dead branches or discoloured foliage which can be observed during late summer. Feeding by the larvae kills branches and eventually the trees (approx. 1-4 years). See Figure 1.

Epicormic shoots: These shoots are also called suckers, water sprouts or witches broom and are produced on the tree trunk and roots when the tree is under stress. They can sometimes be found in the tree crown, on stems and on larger branches. Not all trees attacked by the Emerald Ash Borer develop epicormic shoots. However, under the right conditions and intensity of attack by the beetle, they can develop and grow quickly. See Figure 2.

Woodpeckers feed on the larvae under the bark. Look for increased Woodpecker feedings or signs of their robing in the bark. See Figure 3.

Close examination of the bark may reveal D-shaped holes. When new adults emerge from the tree they create this hole to leave the tree. These holes are approximately 3.4 to 4 mm wide. See Figure 4.

Vertical splits of the bark 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. See Figure 5.

If the bark is peeled back S-shaped tunnels may be visible. This is from the larva feeding between the bark and sap wood. See Figure 6 and 7.

What chemical controls are available?

TreeAzin™ is a systemic insecticide injected into the tree's bark, directly into the conductive tissues, and moves upward with the flow of water and nutrients. It kills EAB larvae feeding on the tree's tissues by regulating growth and disrupting normal molting. It does not pose any health risk to people, pets or wildlife and degrades naturally. To be effective, it is injected into the tree every year for 2 years, then skip a year, then injected for the next 2 years.

How will EAB impact the Urban Forest in Cornwall?

Ash trees make up approximately 25% of the town's urban forest, on public property and 25-30% on private property. The Urban Forest has an inherent value and provides us with numerous benefits - helping clean the air we breathe, shading us from harmful UV rays, beautifying our city and many others. Untreated ash trees are expected to be impacted or killed by EAB over the next 10 years.

What is the City of Cornwall doing about EAB?

The City is currently implementing its EAB Management Strategy, which aims to reduce the significant aesthetic, environmental and financial impacts of the EAB. This is being done through a combination of monitoring, treatment, ash tree removal and replacement, and public education. Private property owners are responsible for trees on their property.

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. If you see signs that your ash tree is dead or dying, you should contact a professional tree care company. 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 should I do if an ash tree on my property is infested?

Property owners who suspect an EAB infestation are encouraged to contact a professional arborist. Private property owners are responsible for trees on their property.

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. 2264. The tree will be assessed by a certified arborist and appropriate best arboricultural practices will be applied to maintain the urban forest.

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Larry Legue
Parks & Landscape Supervisor
Box 877, Cornwall ON, K6H 5T9
Phone: 613-930-2787 ext. 2239
Fax: 613-930-7448
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