How Do I Know If My Trees Have EAB?
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The visual symptoms associated with emerald ash borer infestations are nearly identical to those we often see on ash that are infested or infected by other ash pests and diseases commonly found in Wisconsin.
For example, crown dieback can result from multiple stressors including 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 or more symptoms or signs
(see list directly below) when trying to determine the presence of emerald ash borer in your ash tree. If you see two or more of these please report your findings here.SymptomsCrown dieback:
Dieback of the upper and outer crown begins to occur after multiple years of EAB larval feeding. Trees begin to show dead branches throughout the canopy, beginning at the top. Larval feeding disrupts nutrient and water flow to the upper canopy, thus resulting in leaf loss. Foliage in the top of the tree may be thin and discolored. An example of this is shown below.Epicormic Sprouting:
Stressed trees will attempt to grow new branches and leaves where they still can. Trees may sucker excessively both 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 feed on emerald ash borer larvae located under the bark. Feeding is typically evident higher in the tree where the emerald ash borer prefers to attack first. Large numbers of larvae under the bark can lead to woodpecker damage that looks like strips of bark have been pulled off of the tree. This is called "flecking." An example of this is shown below.SignsD-shaped emergence holes:
As adults emerge from under the bark they create an emergence hole ~ 1/8 inch in diameter and D-shaped. An example of this is shown below.S-shaped larval galleries:
As larvae feed under the bark they wind back and forth, thus creating galleries that are packed with frass 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. Mature larvae reach 1 1/2 inches in length and all larvae are found feeding beneath the bark. Adults:
Adult beetles are metallic green in color and are 3/8 - 1/2 inch in length and 1/16 inch in width. Adults are flat on the back and rounded on their underside.
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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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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