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Why is EAB important?
What does EAB Look Like?
What does an Ash Tree Look Like?
How Do I Know If My Trees Have EAB?
Where has EAB been found?
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How Do I Know If My Trees Have EAB?

The signs and symptoms of an EAB attack

The symptoms an ash tree shows when it is infested with emerald ash borer are similar to symptoms caused by other ash pests or diseases in Wisconsin.

For example, crown dieback can occur due to EAB damage, but can also be the result of drought stress, soil compaction or verticillium wilt, just to name a few.

Therefore, it is important to look for a combination of at least two symptoms or signs when trying to figure out if emerald ash borer is in your ash tree. If you see two or more from the lists below report your findings here.


Crown dieback: Dieback of the upper and outer crown begins after multiple years of EAB larval feeding. Trees start to show dead branches throughout the canopy, beginning at the top. Larval feeding disrupts nutrient and water flow to the upper canopy, resulting in leaf loss. Leaves at the top of the tree may be thin and discolored. An example of this is shown below.

Epicormic Sprouting: When trees are stressed or sick, they will try to grow new branches and leaves wherever they still can. Trees may have new growth at the base of the tree and on the trunk, often just below where the larvae are feeding. An example of this is shown in the picture above, where small branches are growing on the trunk, about 6 feet off the ground.

Bark splits: Vertical splits in the bark are caused due to callus tissue that develops around larval galleries. Larval galleries can often be seen beneath bark splits.

Woodpecker feeding: Woodpeckers eat emerald ash borer larvae that are under the bark. This usually happens higher in the tree where the emerald ash borer prefers to attack first. If there are large numbers of larvae under the bark the woodpecker damage can make it look like strips of bark have been pulled off of the tree. This is called "flecking." An example of this is shown below.


D-shaped emergence holes: As adults emerge from under the bark they create a D-shaped emergence hole that is about 1/8 inch in diameter. An example of this is shown below.

S-shaped larval galleries: As larvae feed under the bark they wind back and forth, creating galleries that are packed with frass (larva poop) and sawdust and follow a serpentine pattern. An example of this is shown below.

Larvae: Larvae are cream-colored, slightly flattened (dorso-ventrally) and have pincher-like appendages (urogomphi) at the end of their abdomen. By the time larvae are done growing they are 1 1/2 inches long. Larvae are found feeding beneath the bark.

Adults: Adult beetles are metallic green and about the size of one grain of cooked rice (3/8 - 1/2 inch long and 1/16 inch wide). Adults are flat on the back and rounded on their underside.

Related Documents
Signs and symptoms (what to look for) of an emerald ash borer infestation.

EAB Pest Alert from the US Forest Service. Images and information on emerald ash borer.

MI Extension bulletin showing look-alikes that are easily mistaken for emerald ash borer.


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Related Images

Example of ash tree dieback. One of the common symptoms of EAB infestation, but also present with other tree ailments.

An example of the S-shaped patterns, called galleries, that EAB larvae create as they feed under the bark of ash trees. This piece of bark has its outer layer removed so the galleries are visible, but usually the outer bark hides this sign of EAB infestation.

An example of a D-shaped emergence (or exit) hole. The very small hole (1/8 of an inch) is a sign of emerald ash borer infestation. NOTE: other wood boring beetles also leave exit holes in trees. The tiny size AND D-shape are characteristic of EAB.

"Woodpecker flecking," as shown here, may occur when woodpeckers feed aggressively due to high numbers of insects inside a tree. Look for small strips of bark missing from high branches of ash trees as one clue to a potential emerald ash borer infestation.

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