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NEW VIDEO: How to Look for Emerald Ash Borer Now

The Emerald Ash Borer attacks ash trees.
Photo: Jeffrey Hahn, Extension Entomologist
Now is a great time to examine your ash trees for evidence of emerald ash borer (EAB).  It may seem early, that you need trees leafed out to properly inspect your ash.  However, the health of the canopy is not a good indicator of whether your ash is infested by this invasive insect pest.  In fact, having a leafless tree makes it easier to search for EAB clues.

Not sure what to look for? We've created this video to show just how you can identify this pest in/on the ash trees in your yard.

Symptoms to look for

Probably the best symptom to look for is woodpecker pecking. Woodpeckers love to eat EAB larvae.  Because of their pecking, they chip off bark, creating a blonding effect, and make holes.  Although woodpeckers eat other insects, their presence on an ash tree is definitely a red flag for EAB infestations.

If you see small, 1/8th inch sized D-shaped exit holes, that is a sure symptom of EAB.  Unfortunately, they are easy to overlook because of their size.  Also, EAB starts infesting trees at the top of the canopy and then work their way down.  Unfortunately, you won’t see these emergence holes until a tree has been infested for a while.

Another definitive symptom is S-shaped galleries found under the bark.  If you see these galleries, that is sure evidence of EAB.  But because they are hidden, they will not be seen unless the bark is removed. 


If you are not sure whether your ash has EAB, contact an arborist to inspect your tree.  The closer you are to known infestations of EAB, the greater the risk of infestation.
For more information, including management of EAB, see Emerald ash borer in Minnesota.

Author: Jeffrey Hahn, Extension Entomologist

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