Signs and Symptoms of emerald ash borer

Cities can create an unnatural habitat for trees. Air pollution, compacted soils, elevated temperatures, and limited access to soil moisture create chronic stress.

Their response to these stressors result in symptoms we can see. These symptoms and signs can be useful hints to investigate further.

The information on this page will help you to recognize, record your observations on the provincial iNaturalist Project page, and/or report to your local municipality.

Let’s review the signs and symptoms that are associated with emerald ash borer (EAB).

~ Level 1 Observation ~

Possible Signs and Symptoms of EAB

Thinning/Dieback of upper tree canopy.

Spot the slow thinning of the tree canopy in the photos below.

The photos with a yellow star would be a tree to consider reporting to local authorities.

Epicormic Shoots at base or mid-way up tree trunk.

These shoots are a survival mechanism meant to rapidly produce new leaves for photosynthesis (regeneration) following a stressful event.

Vertical Splits in the bark.

When EAB larvae feed, they create S-shaped or serpentine galleries filled with insect frass/spit that looks like sawdust.

When the tree tries to heal itself, it creates tissues similar to a callus that pushes the outer bark out creating cracks that run up and down the trunk.

~ Level 2 Observation ~

Probable Signs and Symptoms of emerald ash borer

Bark flaking/flecking from woodpecker feeding activity

Bark flaking or Blonding, looks like white/blonde patches created by woodpeckers searching for their next meal.

~ Level 3 Observation ~

Definite Signs of emerald ash borer

D-shaped exit holes in outer bark.

Once the larvae have fully matured, the beetles will exit from the tree to lightly feed on leaf margins and start mating.

These exit holes are difficult to spot as they measure only 3-4 millimeters or 1/8” in diameter.

They are uniquely D-shaped as opposed to a round circle which can look like lesser-damaging borers.

emerald ash borer beetle(s) found on leaves, bark, and/or flying around the tree.

Quick Recap

ReportD-shaped exit holes and/or beetleson leaves, bark, or flying nearby for immediate inspection.

Report a lot of dieback and blonding/flecking on the outer bark for inspection.

Keep observing if tree has some dieback throughout Summer and late Fall.

What to do if you find an emerald ash borer beetle:

Capture. Place in a clean plastic bottle to avoid crushing. This makes it easier to identify. Be sure to record the exact location of the tree where it was found.
Contain. Place the container in the freezer. This will preserve the insect for closer inspection.
Call. If you reside in Edmonton, Calgary or Lethbridge call 311. Other centers please call 1-877-837-ELMS to immediately report your finding.

Signs and Symptoms of emerald ash borer

Cities can create an unnatural habitat for trees. Air pollution, compacted soils, elevated temperatures, and limited access to soil moisture create chronic stress.

Their response to these stressors result in symptoms we can see. These symptoms and signs can be useful hints to investigate further.

The information on this page will help you to recognize, record your observations on the provincial iNaturalist Project page, and/or report to your local municipality.

Let’s review the signs and symptoms that are associated with emerald ash borer (EAB).

~ Level 1 Observation ~

Possible Signs and Symptoms of EAB

Thinning/Dieback of upper tree canopy.

Spot the slow thinning of the tree canopy in the photos below.

The photos with a yellow star would be a tree to consider reporting to local authorities.

Epicormic Shoots at base or mid-way up tree trunk.

These shoots are a survival mechanism meant to rapidly produce new leaves for photosynthesis (regeneration) following a stressful event.

Vertical Splits in the bark.

When EAB larvae feed, they create S-shaped or serpentine galleries filled with insect frass/spit that looks like sawdust.

When the tree tries to heal itself, it creates tissues similar to a callus that pushes the outer bark out creating cracks that run up and down the trunk.

~ Level 2 Observation ~

Probable Signs and Symptoms of emerald ash borer

Bark flaking/flecking from woodpecker feeding activity

Bark flaking or Blonding, looks like white/blonde patches created by woodpeckers searching for their next meal.

~ Level 3 Observation ~

Definite Signs of emerald ash borer

D-shaped exit holes in outer bark.

Once the larvae have fully matured, the beetles will exit from the tree to lightly feed on leaf margins and start mating.

These exit holes are difficult to spot as they measure only 3-4 millimeters or 1/8” in diameter.

They are uniquely D-shaped as opposed to a round circle which can look like lesser-damaging borers.

emerald ash borer beetle(s) found on leaves, bark, and/or flying around the tree.

Quick Recap

ReportD-shaped exit holes and/or beetleson leaves, bark, or flying nearby for immediate inspection.

Report a lot of dieback and blonding/flecking on the outer bark for inspection.

Keep observing if tree has some dieback throughout Summer and late Fall.

What to do if you find an emerald ash borer beetle:

Capture. Place in a clean plastic bottle to avoid crushing. This makes it easier to identify. Be sure to record the exact location of the tree where it was found.

Contain. Place the container in the freezer. This will preserve the insect for closer inspection.

Call. If you reside in Edmonton, Calgary or Lethbridge call 311. Other centers please call 1-877-837-ELMS to immediately report your finding.