Signs & Symptoms

Adult EAB

The adult Emerald Ash Borer (EAB) beetle has the following unique characteristics:

  • Bright, metallic green
  • ½” long, flattened back
  • Purple abdominal segments beneath wing covers


Adult beetles are most active during the summer and early fall. If you see the beetle or any signs of infestation, you need to report it immediately. During the late summer, fall and winter months, the beetle’s larvae tunnel deep into the trees they infest. While the EAB larvae are usually hidden from sight under the bark, they have the following characteristics:

  • Creamy white, legless
  • Flattened, bell-shaped body segments
  • A pair of small appendages near the end of its body
EAB Larva

Although you can’t always spot it, the beetle may live in cut wood such as firewood. You can help stop the beetle by not moving firewood. Moving firewood can spread the beetle, its larvae and its eggs to healthy trees. Burn your firewood where you buy it.

The Signs

Since the beetle is difficult to spot, you can look for signs of infestation.

Canopy Dieback
Canopy Dieback

Canopy dieback begins at the top of the tree and progresses throughout the year until the tree is bare.

Epicormic Shoots
Sprouts grow from roots and trunk.

Bark Splitting

Vertical bark splits expose S-shaped galleries beneath the bark.


S-shaped Galleries and D-shaped Exit Holes
Galleries under the bark reveal the back and forth feeding pattern of the EAB larvae.  Adults emerge from D-shaped exit holes, typically 1/8″ in diameter.


Increasing Woodpecker Activity/Damage
Several woodpecker species forage for EAB, creating large holes when extracting larvae.


EAB Lookalikes

The following beetles may be mistaken for EAB.

Bronze Birch Borer
This native beetle attacks stressed birch trees and while they look like EAB, they are darker.

Japanese Beetle

This exotic beetle feeds on the foliage of more than 300 plant species, including many common hardwood trees. Adults are slightly less than ½” long with a broad body.


Six-spotted Tiger Beetle
Common in the eastern U.S., Tiger beetles live near the ground as opposed to in the trees. Adults are ½” long, broad-bodied and usually iridescent green or blue.

Two-lined Chestnut Borer

This native borer attacks stressed and declining oak trees. Adults are dark in color with two lines on the backside.

Two-lined Chestnut Borer


Caterpillar Hunter

Caterpillar Hunter
This large ground beetle is often found under rocks, leaves, and other debris, but it will climb trees to find prey. Adults are roughly 1″ long.