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What trees are killed, and what is the impact?

In North America, emerald ash borer (EAB) attacks and kills most ash trees regardless of their species, health, size or location. Most native ash species are vulnerable, with the possible exception of blue ash (found only in localized areas of southwestern Ontario) which often survives EAB attack. Mountain ash is not a true ash species so is not at risk. All saplings and trees greater than 3-4 cm diameter at chest height are considered vulnerable to EAB. A small number of ash survive and remain healthy in heavily infested areas; these trees are being studied to determine whether they will eventually succumb to infestation or remain resistant to EAB.

ash trees dying of emerald ash borer attack Ash trees dying from emerald ash borer attack.
Image: Chris Gynan, Silv-Econ Ltd.

In cities:
Trees in urban areas perform a variety of important functions including reducing household energy use for heating and air conditioning, attenuating storm water (decreases runoff and flooding), improving air quality, and increasing carbon storage. There are also health, social and aesthetic benefits to urban trees; the presence of urban trees is associated with lower crime rates and higher house re-sale prices, while the loss of ash has been linked to higher death rates in EAB-infested areas of the U.S. All of these benefits will be reduced in ash-dense urban areas until the canopy cover is restored.

In woodlots and forests:
Loss of ash in woodlots and forests will have significant ecological impact where ash makes up a large component of the stand. In forests alongside rivers and streams the loss of ash trees could result in increased stream bank erosion, altered stream water quality and loss of shoreline habitats. Because of this insect's ability to attack and kill all age and size classes of ash, including saplings, the ash seed bank in affected forests will be lost. This means that ash could become a rare species. In forests and woodlots, invasive plant species such as buckthorn outcompete other plant species in the understory; with the loss of ash trees, invasive species may exploit canopy gaps and dominate the stand, preventing trees from regenerating.

emerald ash borer killed ash stand Woodlot with dying ash.
Image: Troy Kimoto, CFIA

Loss of ash species:
Ash wood is strong and resilient and has a broad range of uses. It is used for making sports equipment (e.g. hockey sticks and baseball bats), tool handles, furniture, veneer and flooring. Black ash is used by some First Nations communities to make traditional woven baskets. If ash species are lost or drastically reduced in population, this will have both economic and cultural consequences.

See a more detailed version of EAB impacts.

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