The arrival of emerald ash borers in Oregon will bring changes to NW streams and urban forests


The bush pest emerald ash borer is found for the first time in Forest Grove, Oregon. The long-awaited arrival of this invasive insect in Oregon threatens ash trees in the state’s forests, cities and towns as it kills both wild and urban ash trees.

SALEM, Ore – The long-awaited arrival in Oregon this summer of the devastating emerald ash drill has heightened concerns about the impact on urban forests, wetlands and streams.

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

“Since it was first found in the Detroit, Michigan area in 2002, EAB has become the most destructive and costly forest pest that has ever invaded North America,” Williams said. “This small insect (it’s only half an inch long and one-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 places. At least five species of native species to the central US, criticism has threatened as EAB spreads across the country, killing hundreds of millions of urban and wild ash trees.

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 as (Fraxinus latifolia) is a deciduous hardwood tree that is most common in wetlands and along streams. “It is an ecologically essential tree, as it darkens water and keeps it cooler for fish. The roots stabilize stream banks, which reduces erosion. And many animals, birds and insects eat the seeds and leaves. Losing it is likely to have a huge impact on those ecosystems, ”Williams explained.

“ODF used the advance notice that EAB was heading west to collect seed from across the Oregon axis range in the state,” Williams said. “The first goal is to try to preserve as much of the tree’s genetic diversity as possible before it is lost. The US Forest Service’s Dorena Genetics Resource Center in Cottage Grove stores the ash seeds and shares them with researchers. The researchers will test for any resistance to EAB. If any are found, we may be able to breed resistance in local tribes and replant streams. ”

Urban forests will see impacts

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 plague and has plans in place to deal with the loss of ash trees.”

Altenhoff advises cities and towns to do three things this summer if possible.

“In the first place, if this has not already been done, inventory trees to see how vulnerable the local urban forest is to losses of emerald ash borer. We have a common software called TreePlotter that is free for communities to use. “As data comes in from across the state, it will give us a general picture of where all the vulnerable urban trees are,” Altenhoff said.

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

“Finally, consider how wood from ash trees that die from emerald ash drills can be used locally,” Altenhoff said. “There may be opportunities to help local woodworkers and artists and prevent the wood from perishing. But it is crucial that people do not move ash or any other wood outside their local area. It prevents people from accidentally spreading wood-borne pests faster than they would otherwise do. ”

While the beetle does not bite or sting and is otherwise harmless to humans, pets and animals, it has proven deadly in another way. “Research has 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 loss of urban trees is harmful to people, ”Altenhoff said.

He advises communities to prioritize the removal of ash trees that already have poor health or that grow in spaces too small for them. “Starting as a replacement gradually will cost and impact better spread than waiting for a massive death,” Altenhoff said. “Fortunately, there are many alternative tree species, including Oregon white oak, incense cider and Chinese pistachio, which may be more heat and drought resistant than ash.”

To report emerald ash drill sightings, please report online at the Oregon Invasive Species Council hotline. Check out the state’s plan for EAB here.

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

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