EAB Symptoms in Ash Trees

Emerald Ash Borer (EAB) quietly infests ash trees for 4-5 years before the first symptoms are noticed. You will almost never see the shiny green adult insect nor the D-shaped exit holes that it makes when the adults chew their way out of the tree.

Instead, the most common way that EAB is identified in a community is when someone reports high populations of woodpeckers, ‘blonding’ on the south side of the trees, and canopy dieback.

‘Blonding’ is what happens when woodpeckers are looking for EAB larval worms under the bark. The worms are chewing and tunneling in the green tissue between the outer bark and the hardwood. The woodpeckers listen and then start removing old, grey bark so that they can hear better. Then they peck out, and eat the worm from shallow, generally oval-shaped holes. The removal of the old bark exposes inner bark which is light tan, or blond, in color. Look for this symptom in the middle area of the tree and especially on the south side of trees in winter and early spring. Binoculars may help.

Trees that exhibit blonding may also have a split in the bark that expose the inner wood. This is usually over areas where the larval worm fed and killed the inner tissue. You can often see the tunnel inside of the window created by the spilt bark.

Ash trees that have been healthy but suddenly develop dead, leafless areas of the crown should be considered suspicious. Do not confuse this with leaf drop from anthracnose in the spring! (Those leaves should regrow and the branches will stay alive.)

If you have questions or would like someone to look at a suspicious tree, please call City Hall at (701) 652-2911.