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Emerald Ash Borer



Authors as Published

Eric R. Day

Coleoptera: Buprestidae, Agrilus planipennis Fairmaire

Plants Attacked: Emerald ash borer (EAB) attacks all species of ash trees that grow in Virginia. Only Asian species of ash trees have shown any resistance to this pest.

Description of Damage: The first indication of damage by the emerald ash borer is canopy dieback. Tunneling by the larvae cause girdling and death of branches and the trunk. Early feeding damage by emerald ash borer will be difficult to detect because trees show few symptoms. As the infestation progresses the trees starts to thin out and branches in the top sections of the tree start to die. Many trees will have a large number of new shoots on the trunk called epicormic branching. Often these branches occur at the junction of the live and dead sections of the trees. Epicormic branching may also occur at the base of the tree after the tree has died. EAB can live in twigs as small as 1 inch in diameter but can also breed in trunks of fully mature trees. It usually takes 2-5 years for the EAB to kill the tree.


image Image 1. Infested ash tree. Note epicormic branching on trunk and dead branches.

Identification: Adult beetles are about 1/2 inch long and bright metallic green in color. When the wings are spread, the exposed abdomen is purple-red in color. The larvae are creamy white and have a tan head. At the end of the abdomen is a pair of pincher like projection. EAB can also be identified by its damage. As the adult beetle exits its gallery from under the bark it leaves a characteristic “D” shaped exit hole about 1/4 inch in diameter. Removing the dead bark near the exit hole will reveal numerous “S” shaped tunnels under the bark in the cambium area. Woodpeckers will often visit infested trees and leave large jagged holes after they have fed on the EAB larvae. Unfortunately they do not provide complete control for this pest.


image Image 2. Adult emerald ash borer in larval tunnel.

Life History: The emerald ash borer has a one to two-year life cycle. The adult beetles start emerging in May and early June and beetle activity peaks between mid-June and early-July. It is possible to see beetles as late as August. Beetles live from about 3-6 weeks, feed on foliage by making small notches on the outer edge. The female usually lays between 50-100 eggs one at a time in bark cracks and crevices. Eggs hatch in about a week and the newly hatched larvae borer though the bark down into the cambium layer under the bark. Larvae feed under the bark during the summer and they are usually done by fall but stay in the larval stage until spring when they pupate. Newly molted adults remain under the bark for a few weeks until emerging to start they life cycle again. If degreeday information is available, EAB adults start emerging at about 500 degree days (base 50 degrees F.) and the peak is at about 1000 degree days.

Control: Infested trees rarely recover and need to be removed and destroyed or chipped as soon as possible. Non-infested ash trees can be treated to avoid infestation but it’s hard to predict when the emerald ash bore will arrive in a particular county or city in Virginia. If you live in an infested county or an adjacent county you may want to consider using a systemic insecticide, applied as a soil drench a the base of plant in May or early June before the tree becomes attacked. Contact your local Cooperative Extension office to see if your location is infested or near an infested county. Your extension office can also provide the most current information on chemicals labeled for control.


image Image 3. Trunk of tree girdled and killed by emerald ash borer. Note “S” shaped tunnels.

Movement of Firewood: Emerald ash borer has been detected and moved by firewood in the United States and thus its important to remove and destroy infested ash trees on site. It’s also important when camping to leave firewood at home and purchase firewood at the campground from local sources.

Remarks: The emerald ash borer is native to Asia and was found in Michigan in 2002. It is not known how it was brought into this country. The first infestation in Virginia in 2003 was eradicated but it was found again in 2008 and had a wide distribution in parts of Northern Virginia.


Photos by Eric R. Day


Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.


Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Interim Administrator, 1890 Extension Program, Virginia State University, Petersburg.


May 1, 2009

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