Oregon Ash Trees Face Growing Threat as Emerald Ash Borer Reaches New Willamette Valley Sites

The highly destructive emerald ash borer (EAB) was found in three new communities across the northern Willamette Valley this month, and officials warn these can quickly spread to surrounding trees if measures aren’t put in place.

Borer Beetles in Willamette Valley

Oregon Department of Forestry (ODF) confirmations place the tree-killing pest in high-traffic commercial parking lots in Tualatin and Newberg, as well as a residential property in Silverton.

The agency said the spread is expected, but the timeline is hitting a critical tipping point.

Data from previously infested states shows that four to five years after initial detection, localized pockets of EAB rapidly explode into widespread, county-wide infestations.

For property owners and municipalities, this ceases to be just an environmental issue and becomes a financial liability.

The EAB Quarantine Zone is Clackamas, Marion, Multnomah, Washington, & Yamhill counties. A strict rule has been put in place: No transport of ash, olive, white fringetree material, or any hardwood firewood outside these boundaries.

Dead or rapidly dying ash trees rapidly become brittle, making them very hazardous to climb or work under. Forestry specialists warn that removing a dead ash tree is far more dangerous and expensive than removing a live one.

Municipalities and homeowners face an immediate choice: treat or remove borer-infested trees:

• Protective Treatment: Property owners wishing to save high-value ash trees must contact a licensed pesticide applicator immediately to begin systemic insecticide injections.
• Pre-emptive Removal: If an ash tree is already in poor condition, experts recommend pre-emptive removal. However, to prevent the spread of active infestations, removal should be delayed until mid-October, when adult beetles stop flying.

The Tualatin detection is particularly concerning, as it sits just a mile from the Tualatin River’s heavily shaded ash banks. Local officials are already allocating a budget for extensive canopy surveys and mitigation.

All three new detections were flagged by everyday citizens utilizing the Oregon Invasive Species Hotline.

Residents noticing canopy dieback, D-shaped exit holes, or larval galleries under the bark should report sightings immediately at https://oregoninvasiveshotline.org.