Signs of EAB

Early detection of an EAB infestation is difficult. If you want to protect your ash against EAB, preemptive treatment is strongly recommended. This will remove the burden and worry of being on constant lookout for the signs and symptoms of an infestation. Unless you keep a careful watch on your tree and know exactly what to look for, you run the risk of not detecting an infestation early enough for insecticide treatment to work. If you decide to postpone treatment and are willing to diligently monitor your ash for EAB, you could detect an infestation early enough for insecticides to work.

The following visual aids show the signs and symptoms of an infestation that you need to be on the lookout for:

  4. An adult EAB beetle is bullet shaped and about one-half inch long and one-eighth inch wide. Its back is dark metallic green, and its underside is bright emerald green. See the link below for look-alikes. Photo by Renee Pinski, WDNR.

  4. The violet-colored abdomen of an adult EAB beetle flaring its wings. Photo by David Cappaert, Michigan State University, Bugwood.org.

  4. Bark flecking caused by woodpeckers is likely the first sign of an EAB infrestation. Jagged holes and patches of flecked off bark could mark spots where woodpeckers have repeatedly drilled for EAB larvae. Photo by Steven Katovich, USDA Forest Service, Bugwood.org

  4. Thinning of a tree's canopy or dieing branches could indicate the presence of EAB. Branch dieback alone can be caused by a variety of natural diseases and insects. EAB is more likely if suckers (sprouts) also appear anywhere on the tree below dead branches. A tree sends out suckers to compensate for lost foliage. Photo by Jane Cummings Carlson, WDNR.

  4. Vertical bark splits on the trunk develop in areas where larvae have fed, often revealing their S-shaped excavation paths. This usually points toward an advanced infestation as larvae have bored inward from eggs deposited on the trunk. Most branches are dead so larvae must feed where food is available. Photo by Linda Williams, WDNR.

  4. When an EAB beetle emerges (late May-mid July), it leaves behind a D-shaped exit hole, about one-eighth inch in diameter. Holes can be oriented in any direction and found anywhere on the trunk. Also check lower branches. Look for holes if you notice any other signs or symptoms of an EAB infestation. Photo by Renee Pinski, WDNR.
Early detection of emerald ash borer is difficult, especially on large trees, because beetles attack the top first. Furthermore, dieback of branches in the upper crown can be caused by insects other than EAB. Unless a tree is heavily infested, chances of seeing an adult EAB beetle are extremely rare. Nevertheless, be aware that if you spot a green beetle on an ash trunk, branch, or leaf it could be EAB or it might be a look-alike beetle.

Reporting EAB


If you are sure you have an ash tree and notice signs or symptoms of EAB on it, please first call the City Forester. If he is unavailable, leave a message and call the Director of Parks, Recreation, and Urban Forestry. Leave a message if necessary. If you speak with neither directly, then call the Department of Agriculture, Trade, and Consumer Protection’s EAB hotline. E-mailing digital photos of your tree to the City Forester or Parks Director is encouraged.

Anna Healy, Fitchburg City Forester
608-270-4289
anna.healy@fitchburgwi.gov

Scott Endl, Director of Parks, Recreation, and Urban Forestry
608-270-4288
scott.endl@fitchburgwi.gov

Wisconsin Department of Agriculture, Trade, and Consumer Protection EAB Hotline: 1-800-462-2803