PORTLAND, Ore. (KOIN) – The Oregon Department of Agriculture issued a temporary emerald ash borer quarantine in Washington County in December to help prevent the spread of the invasive insect. 

The temporary quarantine began December 20 and will be in effect until May 16. The quarantine prohibits tree materials from all ash, olive and white fringe trees from being moved to places outside Washington County. 

This includes logs, green lumber, nursery stock, scion wood, bud wood, chips, mulch, stumps, roots, branches and firewood of hardwood species.  

So far, the emerald ash borer has only been detected in Washington County and state officials are working to prevent it from spreading to other Oregon counties. 

The invasive pest was first discovered in Oregon in June 2022 when it was spotted on several ash trees in Forest Grove. This was the first confirmed sighting of the emerald ash borer on the West Coast. 

The insect has not been detected anywhere else in Washington County outside of Forest Grove. 

These invasive and destructive beetles have killed up to 99% of the ash trees in some North American locations. At least five ash species native to the Central U.S. have become critically endangered as the emerald ash borer spreads across the country. 

The emerald ash borer has also decimated ash trees in parts of North America outside the U.S., and in Europe. Its larvae burrow into the bark of ash trees, causing the canopy to die, which will ultimately result in impacted trees dying. 

Within a decade of the emerald ash borer’s arrival in an area, most ash trees will be dead or dying, the Oregon Department of Forestry said, putting the state’s native Oregon ash tree at risk. 

Researchers say olive trees and white fringe trees could also be impacted and are known to host the insect. That’s why materials from these trees are included in the quarantine. 

The emerald ash borer is about a half-inch long and an eighth of an inch wide. It’s known for its metallic, shiny green color. 

The emerald ash borer is about a half-inch long and is known for its metallic, shiny green color. Photo courtesy Oregon Department of Agriculture.

Signs of infestation include thinning and yellowing leaves on trees, bark splitting, D-shaped holes in tree bark, and basal shoots. 

There are steps the public can take to help control the spread of the emerald ash borer. 

The first is to report any and all sightings of the beetle. Anyone who sees an emerald ash borer should make a report of it online at the Oregon Invasive Species Council Hotline

The Oregon Department of Forestry also recommends towns remove ash trees from their list of approved street trees. 

Officials recommend planting resistant species in place of the ash trees — like Oregon white oak, incense cedar and Chinese pistache. 

The Oregon Department of Agriculture is creating several processing and disposal resources in the Washington County quarantine area to limit the movement of ash, olive and white fringe tree materials. There is a list of tree material disposal sites online

The department said as more data becomes available, it will evaluate future quarantine parameters.