Emerald Ash Borer: What Are The Signs Of An Emerald Ash Borer Infestation?


Date: August 18th, 2010


There are several signs to look for when you assess your ash trees for damage.


Canopy Dieback

The tunnels (called galleries) carved out by EAB larvae disrupt water and nutrient transport within the tree, gradually cutting off the food supply to the branches of your ash tree. Canopy dieback begins in the top third of your tree’s canopy and progresses downward until your tree is bare of its leaves.


Epicormic Shoots

Epicormic shoots are extra sprouts that grow upwards from the tree’s roots or outwards from its trunk. Also, the leaves on these extra tree growths are often larger than normal. Epicormic shoots generally appear on a stressed or injured tree; therefore, with ash trees, these shoots can certainly be a sign of an emerald ash borer infestation.


Serpentine Galleries

The larvae carve tunnels called galleries into the wood of ash trees just underneath the outer bark layer. These galleries weave back and forth across the grain of the wood, disrupting the water and nutrient transport within the tree. If you peel back the bark from a small area of your ash tree and find these serpentine galleries, you can be sure that your tree is infested with emerald ash borers.


Bark Splitting

Vertical fissures in the bark of your ash may also form, as the tissues of the tree change with the activities of the emerald ash borers. The larvae feed on the living tissues of the tree as they carve out their serpentine galleries in the wood. This damages the tree and causes it to form callus tissue (essentially scar tissue). This callus tissue requires more physical space than the living phloem tissues did in the tree, so the bark is forced to split open to allow for the callus tissue to grow. It’s also possible that you will be able to see the winding galleries through these splits in the bark.


D-Shaped Exit Holes

After the larvae have developed into adult emerald ash borers, they emerge from the tree through the outer layer of bark, leaving D-shaped exit holes.


Increased Woodpecker Activity

There are several woodpecker species that feed on the emerald ash borer in its larval and pupal stages. If your ash tree is infested with EAB, there will likely be more woodpeckers attracted to your tree as well. Because these birds create large holes to extract the insects from the tree, the outer bark of your ash tree may have more woodpecker damage than normal.



Click here for more descriptions and pictures of ash trees and emerald ash borers.


Additional Resources: http://www.emeraldashborer.info/files/E-2938.pdf

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