Emerald Ash Borer

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The EAB is an invasive species that feeds under the bark of ash trees and is currently destroying the ash tree population of North America. All species of ash are susceptible to attack, except mountain ash, which is not a true ash species.

Since it was first identified in Michigan in 2002, EAB has killed millions of ash trees in Ontario and many parts of the United States. It poses a major economic and environmental threat to urban and forested areas. It was confirmed in Ottawa in 2008 and its impacts can be clearly seen spreading from the St. Laurent area.

Since the insect spends most of its lifecycle under the bark of trees, it can be easily moved with firewood or other tree materials such as nursery stock, logs, brush and larger wood chips.

EAB is one of the main reasons why Ottawa will be losing 25% of its tree cover in the next 3 to 5 years.


Emerald Ash Borers normally have a one-year life cycle, but some can take up to two years to mature. EAB lays eggs on tree bark and in bark crevices starting in late May.


Iashborern its larva form, which resembles a caterpillar, Emerald Ash Borer feeds just under the bark of ash trees. This feeding disrupts the tree’s circulation of water and nutrients. The presence of even a few insects in a tree can kill it.

Top branches of ash trees usually die off first. Trees can lose half its branches in a single year. Once larvae finish feeding under the bark, they mature into adult beetles that chew their way out of the tree.

S-shaped grooves and D-shaped exit holes 3.5 – 4 mm wide caused by adult beetles.
9596776-largeLook for loss of leaves and dead branches in the upper part of ash trees
  • unusually thin tree crowns
  • branch and leaf growth in the lower part of the stem where growth was not present before
  • unusually high woodpecker activity
  • look for bark splitting, S-shaped grooves beneath the bark caused by larval feeding, and D-shaped
  • exit holes 3.5 – 4 mm wide caused by adult beetles

Infested ash trees in North America generally die after two to three years, but heavily infested trees have been observed to die after one year.

It is prohibited by law to move ash tree material and any kind of firewood from one location to another in many areas of Ontario and Quebec. This regulation is in place to slow the spread of the Emerald Ash Borer. If you are camping, and you do not use up all of your firewood, leave it behind. Do not pack it up to take home, or to your next camp-site. Violation of this regulation will result in fines and/or prosecution.


  1. Random Patterns- Photo Exhibit of Impact of Emerald Ash Borer | Tree Ottawa - November 24, 2014

    […] Emerald Ash Borer […]

  2. Ottawa’s Trees | Green Living Ottawa - September 22, 2015

    […] are also at risk—from development and infill, threats such as the emerald ash borer, and challenging growing […]

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