Step by Step: Identify EAB damage

December 9, 2014 -  By

Infestations of the Emerald Ash Borer (EAB) once were confined to the Upper Midwest U.S. Now they’re in Canada, as far east as New Hampshire and as far west as Colorado—and spreading further. Not to mention, one researcher has found evidence the invasive green beetle now is attacking the white fringetree, an ash relative.

Here are some tips for you and your crews to ID an EAB infestation. If you find a damaged tree in your area, report it to your county extension office or visit and click on “Reporting EAB.”

-Many symptoms shown by EAB-infested ash trees resemble symptoms caused by other pests or diseases. If several symptoms or signs of EAB are present at the same time, you may have an infestation. Examples include: crown dieback or thinning at the top of the tree, which happens after several years of larval feeding; suckering or epicormic sprouting, which is new growth at the base of the tree and on the trunk (Step 1); and vertical splits in the bark or woodpecker flecking, which looks like strips of bark have been pulled off of the tree (Step 2).

-One sign includes the presence of EAB adults or larvae. Adults emerge from under the bark, creating a D-shaped emergence hole (Step 3). As larvae feed under the bark they wind back and forth, creating galleries that are packed with frass and sawdust and follow a serpentine or S-shaped pattern.

-Adult beetles are metallic green and about the size of one grain of cooked rice (3/8 inch to 1/2 inch long and 1/16 inch wide). Adults are flat on the back and rounded underneath. EAB larvae are cream-colored, slightly flattened and have pincher-like appendages at the end of their abdomens. By the time larvae are done growing they are 1 1/2 inches long.

Step 1

Look for new growth at the base of the tree and on the trunk (this is often just below where the larvae are feeding). When trees are stressed or sick, they’ll try to grow new branches or “suckers” and leaves wherever they can.



Step 2

Notice any areas where bark has split vertically. Woodpeckers also may feed on the beetle, leaving visible damage on the bark.


Step2_bark_split Illustrations:


Step 3

Check trees for D-shaped emergence holes. As adults emerge from under the bark they create a unique hole about 1/8 inch in diameter. It may be anywhere on the trunk or upper branches.




Sources: Wisconsin’s Emerald Ash Borer Information Source, Iowa State University Extension Service, Illinois Department of Agriculture,


This article is tagged with , , , and posted in 1214, Step by Step

Comments are currently closed.