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(Photo of an Emerald Ash Borer)

The emerald ash borer is a pest that has been destroying ash trees across the country. It was first detected in the U.S. in Michigan in 2002. Since then, the insect has spread to forests and urban areas across the country. It has killed millions of ash trees in the U.S. so far.

It is difficult to determine the exact impact that the Emerald Ash Borer has had on the environment because it is impossible to predict the course that the environment would have taken without the presence of this invasive species. However, the destruction that it has caused has been enormous and has had a serious impact on the ability of the environment to support plant and animal life.

The only way to control this pest is to be proactive and prevent it from spreading. The best way to prevent the spread is to help eliminate the ash trees that are infected and treat trees that have not been infected. It is as simple as that.

If you have an ash tree in your yard, you need to take steps to prevent the devastation that this pest will continue to cause. If we are not proactive, and take the necessary steps to prevent the spread we will have to face the consequences.

The consequences of this pest is not just the loss of your tree or trees but could be the loss of a major forest, the loss of a major food source and the loss of an important ecosystem.

State officials are asking the public to learn what an emerald ash borer looks like and to report any sightings online at the Oregon Invasive Species Council hotline. This will help the state know how far and how fast this destructive insect is spreading in Oregon.

EAB is native to eastern Asia and has spread to about three dozen states since its first detection in Michigan two decades ago. EAB is now considered the most destructive forest pest in North America. Although harmless to people, pets, and animals, it has proven deadly to all ash species in North America and Europe, including the native Oregon ash (Fraxinus latifolia). EAB can also infest American fringe trees (Chionanthus virginicus) and European olive trees (Olea europaea).

The infested ash trees in Forest Grove were cut down and chipped within 48 hours of discovery. ODF and ODA are now working closely with industry partners, including urban foresters and nursery producers, to provide information and resources as Oregon launches a response to the discovery of EAB.

The state is using the Emerald Ash Borer Readiness and Response Plan for Oregon as a guide in its response. The plan was finalized in March 2021 and created through the collaborative efforts of a diverse group of stakeholders and state agencies. The state will be consulting with local and federal governments and providing updates to the public and industry as it moves through its response efforts.

To report sightings of emerald ash borer please make a report online at the Oregon Invasive Species Council hotline. For more information about EAB please visit ODA’s Emerald Ash Borer webpage.

For more information about impacts of EAB to Oregon’s urban forests and the risks to native ash trees please visit ODF’s Forest Health page.

Emerald ash borer arrival in Oregon will bring changes to NW streams and urban forests

SALEM, Ore – The long-anticipated arrival in Oregon this summer of the destructive emerald ash borer sharpens concerns about the impacts to urban forests, wetlands and streams.

Wyatt Williams is the Oregon Department of Forestry’s Invasive Species Specialist. He helped collaborate on the state’s response plan to emerald ash borer (EAB), published in March 2021. And for the past couple years, he has been managing a federal grant to try and save the gene pool of the state’s only native ash species ahead of a pest that could wipe it out.

“Since it was first found in the Detroit, Michigan area back in 2002, EAB has become the most destructive and costliest forest pest ever to invade North America,” said Williams. “This little insect (it’s only half an inch long and an eighth of an inch wide) has spread to 35 states and five Canadian provinces, killing up to 99 percent of their ash trees in some locations. At least five ash species native to the central U.S. have become critically endangered as EAB spreads across the country killing hundreds of millions of urban and wild ash trees.”

(Photo of a canopy damage from Emerald Ash Borers)

Within a decade of EAB’s arrival in an area, most ash trees will be dead or dying. The concern in Oregon is for Oregon ash because of the important ecological role it plays along streams and in wetlands.

Oregon ash (Fraxinus latifolia) is a deciduous hardwood tree found most commonly in wetlands and along streams. “It’s an ecologically vital tree as it shades water, keeping it cooler for fish. The roots stabilize streambanks, reducing erosion. And lots of animals, birds and insects eat the seeds and leaves. Losing it will likely have a huge impact on those ecosystems,” Williams explained.

“ODF has used the advance notice that EAB was heading west to gather up seed from throughout Oregon ash’s range in the state,” said Williams. “The first goal is to try and preserve as much of the tree’s genetic diversity as we can before it’s lost. The U.S. Forest Service’s Dorena Genetics Resource Center in Cottage Grove stores the ash seeds and is sharing them with researchers. The researchers will test for any resistance to EAB. If any is found, we might then be able to breed resistance into local strains and replant streambanks.”

Ash species from the central and eastern United States and Europe are commonly planted as ornamentals in Oregon, said ODF’s Urban and Community Forestry Assistance Program Manager Scott Altenhoff. “The state has been warning communities for years to prepare for this pest and have plans in place for dealing with the loss of ash trees.” Altenhoff advises cities and towns to do three things this summer if possible.

“First, if it hasn’t been done already, inventory trees to see how vulnerable the local urban forest is to losses from emerald ash borer. We have a common software called TreePlotter that’s free for communities to use. As data comes in from around the state, it will give us a common picture of where all the vulnerable urban trees are,” said Altenhoff.

“Second, now is a good time to remove ash trees from approved street tree lists as has been done in Portland. Olive trees, which are in the same family as ash, can also be vulnerable,” he said.

“Finally, consider how wood from ash trees that die from emerald ash borer might be used locally,” Altenhoff said. “There may be opportunities to help local woodworkers and artists and keep the wood from going to waste. But it is crucial that people not move ash or any other wood beyond their local area. That avoids people accidentally spreading wood-boring pests faster than they would otherwise.”

While the beetle doesn’t bite or sting and is otherwise harmless to people, pets, and animals, it has proven deadly in another way. “Research revealed that where the tree canopy was dominated by ash, the rapid removal of all those trees led to higher than expected deaths among residents. So the loss of urban trees is harmful to people,” said Altenhoff.

He advises communities to prioritize removal of ash trees that are already in poor health or growing in spaces too small for them. “Starting to steadily replace ash will spread out the costs and impacts better than waiting for a massive dieoff,” said Altenhoff. “Fortunately, there are many alternative tree species, including Oregon white oak, incense cedar and Chinese pistache, that might be more heat and drought resistant than ash”. To report sightings of emerald ash borer please make a report online at the Oregon Invasive Species Council hotline.

EAB was once thought to be a death sentence for your trees. Now, we know it’s not. You can treat EAB and save your ash trees.

(Emerald Ash Borer size and D-shaped entry hole)


The first step in treating your tree for emerald ash borer is to inspect your tree for any other pre-existing problems. The results of this examination will determine whether your tree is a good candidate for preservation. It is important that the EAB treatment is applied by a certified applicator at the right time, in the right way. When done properly, Emerald Ash Borer treatment can be 85-95% effective.


Treatment options for EAB include soil injection, trunk injection, bark spray, and canopy spray. Injections of soil and trunk are the most common treatments for EAB. Both systems distribute the product evenly throughout the canopy by delivering it directly into the tree's tissue. This injection stops the larvae from tunneling in the tree, which is the most destructive phase of this insect. It is also sometimes necessary to use canopy sprays, which prevent adult borers from feeding and laying eggs. It is possible to limit environmental exposure through systemic applications.


Several factors need to be considered before applying an EAB treatment to make it effective, including the product, dose, application timing, and overall health of the tree. There are products accessible to homeowners that have the same active ingredients that professionals use. However, not all of them contain high enough concentration to be effective. When a tree suffers from a disease such as EAB that could result in its death, it is crucial that the correct dosage of medicine is administered. In this regard, professional tree inspections and treatment programs are highly recommended.


Proactively! Don’t wait! You vastly improve the chances of your trees surviving and optimizing the effectiveness of the treatment when you act early. In other words ASAP! Even if your ash tree still looks healthy, get it inspected! The damage that can be seen today, could have taken place years ago!

(Photo of an Emerald Ash Borer trunk damage)


Depending on how many trees you have and the type of treatment needed, the cost of EAB treatment varies. During a consultation, our Master arborist will be able to give you an exact number. We know, however, that EAB treatment is significantly less expensive than removing a tree. Additionally, you will be able to enjoy the beauty and benefits of your trees when you treat them.


Yes! When applied correctly, EAB treatment is 85 to 95 percent effective. For example, when EAB was detected in Naperville, IL, they treated their trees. Three years later, more than 90 percent of the treated ash trees show no signs of infestation. EAB treatment works to save trees in your yards and your city.

For more information about impacts of EAB to Oregon’s urban forests and the risks to native ash trees please visit ODF’s Forest Health page.

News Reports Cited:


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