About 95,000 ash trees live in Portland, and most of them could become infected and die in the next few years with the recent arrival of the emerald ash borer, an invasive, tree-killing pest that’s already killed huge swaths of ash trees in the Midwest.

Portland’s tree canopy will not look the same over the next decade. For many residents, the first signs of the emerald ash borer’s invasion will appear along the city’s streets.

For years, the city has made a concerted effort to line its streets with trees. According to the Portland Street Tree Inventory Project, more than a quarter million trees live along city streets. Of those, nearly 10,000 are ash trees.

In a recent press release, Cody Holthouse, manager of the Oregon Department of Agriculture’s Insect Pest Prevention and Management Program, said “the pattern of spread in the eastern U.S. has been that populations at first increase slowly and the rate of natural spread is slow. But within a few years there is a rapid build-up in the population and it spreads in all directions at a faster pace. That’s exactly what we’re starting to see with these detections.”

Oregon forestry officials first detected the emerald ash borer in the state in Forest Grove in 2022. Since then, it’s popped up in five other locations in the Willamette Valley and most recently, in the Hazelwood neighborhood in Northeast Portland. Officials say infected trees in the parking lot of the David Douglas Aquatic Center will be removed.

There are nearly 120 ash trees along the streets in the Hazelwood neighborhood, according to the city’s Street Tree Inventory Project. That’s about 1.9% of the 6,325 trees living in the area.

Other neighborhoods with more ash trees could be hit much harder.

One of those neighborhoods is South Portland, which extends from the Ross Island Bridge to the Sellwood Bridge with the Willamette River to the east and Interstate 5 to the west. Of the 4,285 street trees inventoried in the neighborhood, about 12.1% or 517 are ash trees. Macadam Avenue runs through the area, and the majority of the trees along that street are ash trees.

Interactive map: Portland Parks and Recreation monitors ash trees for emerald ash borer

The area with the highest concentration of inventoried ash trees, however, is PDX. Portland International Airport and the surrounding area, including the Columbia Slough, have just 770 street trees, but 206 of them are ash trees — about 26.8%. Dozens of those trees line Northwest Alderwood Road just west of Interstate 205.

Other neighborhoods with a high concentration of ash trees include three areas found in Southwest Portland: Collins View along the Willamette River and south of the Sellwood Bridge; Bridlemile west of Hillsdale and Maplewood west of Multnomah Village.

There’s also a large number of ash trees in the Richmond neighborhood in Southeast Portland; St. Johns in the far northwest corner of the city; Portsmouth just east of St. Johns; and Buckman and Sellwood-Moreland, also in Southeast Portland.

Invasive emerald ash borer has reached Portland, dooming ash

While the emerald ash borer will likely infect and force the removal of many trees along the city’s streets, these street trees make up a small fraction of the ash trees in the city. Officials estimate that about 68,000 ash trees can be found in natural areas in Portland and another 16,000 are on private property.

The invasive beetle targeting these trees is about a half inch long and, despite its iridescence and color, officials say it can be hard to see.

“Finding one in a trap usually means there are quite a few already in that area,” Holthouse said.

Officials plan to continue setting traps to find areas with infestations, and encourage anyone who finds the pest to report it over the phone to 1-866-INVADER or online here.

“If you can capture the beetle in a jar or other container that’s ideal, but at least try and take a clear, close-up photo,” said Kat Bethea, an emerald ash borer specialist for the Oregon Department of Forestry. This helps us identify the insect in question much more easily.”

The state has created a map where people can see if they live in area where the beetle has been detected. Quarantines have been set up in those areas, forbidding the cutting and transfer of firewood out of those areas.

Infected trees can be treated with an herbicide, but in some cases, they need to be removed, officials said.

News Source : https://www.opb.org/article/2025/09/16/portland-oregon-emerald-ash-borer-street-trees/