Everything you need to know about the emerald ash borer (EAB)

November 27, 2014

Emerald ash borers are destroying the lungs of our cities.How can we halt them? By knowing the enemy. Here's everything you need to know about the emerald ash borer.
The emerald ash borer

The emerald ash borer is a metallic green beetle measuring less than 1.5 cm. The beetle is native to eastern Asia and was first discovered in Canada in 2002, likely after hitching a ride on wooden freight containers. Their presence isn’t a problem on their home continent, as trees there have natural defenses against this insect. The emerald ash beetle only attacks ash trees, hence its name.

Ash trees

Ash trees are a temperate forest tree frequently planted in cities because of its unique ability to adapt to urban environments. For example, in Montreal, one out of every five trees is an ash tree. The wood of the ash tree is often used to construct the likes of flooring, furniture and tools.

Damage caused by emerald ash borers (EAB)

Since the emerald ash borer has very few predators and reproduces quickly, they are spreading like wildfire across North America. Unfortunately, our ash trees are not naturally protected against this pest. Since its emergence in the United States and Canada, millions of trees have died or have been chopped down as a result.

How does the emerald ash borer attack the tree?

Larvae are the main cause of tree deterioration: they burrow and destroy layers under the bark responsible for transporting nutrients and water to the top of the tree.

In other words, the borer larvae destroy the blood vessels of the ash tree. If the problem isn’t treated, unfortunately the tree will die within one to five years.

Signs that a tree is infested

  • The top of the tree is bare
  • The base of the trunk is covered with young shoots—this is because the ash tree is trying to find other ways to feed and oxygenate itself
  • The bark comes off easily and furrows are visible under the surface
  • Woodpeckers are more present
  • The bark is cracked
  • Holes in the shape of a “D" are visible on the bark, indicating that emerald ash borer adults have emerged from the tree
  • The leaves of the tree have been damaged


Identifying an infested ash tree on your property is the first step to dealing with these invaders. Once identified, an arborist will take action by:

  • Testing to confirm the presence of the emerald ash borer
  • Laying traps
  • Injecting the tree with a bio-pesticide which, although harmless to humans and the environment, is very effective against the emerald ash borer
  • Chopping down and disposing of dead or unsalvageable trees

Deterioration happens so quickly that only swift action can save an ash tree. The Canadian government has banned the transport of ash wood and all kinds of firewood between different regions. Affected municipalities now have programs in place to fight against the emerald ash borer, going so far as to even setting up a municipal hotline that concerned residents can call.

Everything you need to know about the emerald ash borer (EAB)
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