Emerald Ash Borer

A picture of a green Emerald Ash Borer on a green leaf.

The Emerald Ash Borer is a small, iridescent green beetle with the ability to devastate ash trees, quickly killing so many of them that it even threatens entire ash species.

The first U.S. sighting was in 2002 in Michigan. Within 20 years and despite extensive eradication efforts along the way, the beetle has been found in 35 states.

On June 30, 2022, Oregon became the 36th.

The arrival of the Emerald Ash borer in the Pacific Northwest was unwanted, but not unexpected.

“Emerald ash borer is known for rapidly spreading despite aggressive attempts to stop it,” said Karen Ripley, an entomologist for the U.S. Forest Service Pacific Northwest Regional Office.  “Depending on its search for host trees and local winds, adults commonly fly one to 20 miles, and major jumps have been made across North America when EAB have hitched rides on nursery plants and inside loads of infested firewood.”

Hundreds of thousands of North American ash trees from multiple ash species have died from beetle-inflicted damage, she said.

That’s bad news for the Oregon Ash, Fraxinus latifolia, the northwest’s only native ash tree species and an important part of aquatic and riparian ecosystems. It thrives in wetlands where other species often do poorly, tolerating flooding, stabilizing riverbanks, and providing shade for rivers and streams. Cold water contains more oxygen and lowers fish metabolism, improving survivability for salmon and many other aquatic species.

Both native and non-native ash trees are also an important part of the “urban forest,” where they’ve persisted through development and been planted as decorative trees to produce shade in parks, along sidewalks and parking strips, and on private property.

For example, around eight percent of the urban trees in Eugene, Ore. are Oregon Ash trees, Ripley said

Although some tree species have demonstrated they have natural resistance to invasive pests, the search is just beginning for individual ash that can tolerate Emerald Ash Borer. That’s why the Forest Service’s Dorena Genetic Research Center in Cottage Grove, Oregon and the  Oregon Department of Forestry have been collecting, storing, and testing  Oregon Ash seeds in preparation for the Emerald Ash Borer’s eventual arrival. The saved seeds could help researchers search for insect-resistant, inheritable traits among the offspring of existing trees, and preserve the species’ genome if it proves highly susceptible to damage caused directly by the insect.

“Resistance is rare,” Dr. Richard Sniezko, the research center’s director, said in a video about Saving Oregon Ash. The video was produced by Oregon Department of Forestry just a few months prior to the recent discovery of an Emerald Ash Borer infestation among ash trees in Forest Grove, Oregon.

“Will we get ten percent resistance? I doubt it. Maybe we’ll get one percent. Maybe one-tenth of one percent. But that’s different from saying there’s no resistance,” Sniezko said.

Several groups of Oregon ash seedlings from the Pacific Northwest are now being exposed to EAB in the Midwest to evaluate whether resistance is present. 

Experts say everyone can help slow further spread of the Emerald Ash Borer.

Firewood users can reduce the risk of spreading insect pests and diseases when they “buy it where you burn it”. If allowed, campers should collect dead and downed wood at their campsite or purchase firewood locally near where they camp. If you use firewood for fuel, burn it within 50 miles of where it was cut.  You can also buy certified, heat-treated wood. For more information, visit DontMoveFirewood.org.

Foresters in Oregon and Washington are also asking property owners to check their property for Oregon Ash and other ash tree species –  as well as American fringe trees and European olive trees, which can also be infested by EAB. Once you know where susceptible trees are located, learn how to identify the Emerald Ash Borer, monitor your trees, and report suspected sightings of live beetles or signs of infestation.

The adult Emerald Ash Borer beetle is a brilliant, iridescent emerald green. It’s one-third to one-half inch long, with bulging black eyes and short antennae. The body is long and narrow. When its wings are open the back of the insect is pinkish red, while its underside is bright, metallic green.

The EAB’s wings do not spots, stripes, or grooved patterns. Find a chart with common EAB look-a-likes here.

Signs of EAB infestation include yellow, sparse, partly eaten, or wilted foliage, “D-shaped” exit holes in bark, unusual or increased presence of woodpeckers (or evidence of pecking holes), and fresh shoots growing from the tree’s roots or trunks – often with larger-than-normal leaves.

At the federal, state, and local government level, various methods are being used to reduce the impact and slow the spread of Emerald Ash Borers where infestations occur.

Communities can remove ash species from their recommended tree lists, suggest alternatives for replacing ash trees with species that are less likely to be affected, survey their areas to identify susceptible trees, and establish early-detection and tree health monitoring programs.

Where found, infested trees can be treated with pesticides; felled and burned, chipped or buried; and stingless wasps that preys on the beetle’s eggs or larvae can released as part of an integrated pest management plan.

To learn more about the Emerald Ash Borer and federal response efforts, visit the USDA Animal and Plant Health Inspection Service (APHIS), at: https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/the-threat/emerald-ash-borer/emerald-ash-borer-beetle

Sightings of EAB or symptomatic ash trees should be reported to your state’s invasive species program:

More information: