Portland Parks & Recreation’s (PP&R) Urban Forestry division has developed an emerald ash borer (EAB) Response Plan to manage the arrival of this highly destructive, invasive tree pest. Although EAB has not yet been confirmed in Portland, infestations have already been found in nearby Clackamas, Marion, Yamhill and Washington counties.
EAB is an invasive beetle that attacks and kills all species of ash trees, including the native Oregon ash. Since it was first discovered in Michigan in 2002, it has killed over 100 million trees across the US and is considered North America’s most destructive forest pest.
Portland has an estimated 95,000 ash trees, found in parks, neighborhoods, natural areas and yards. Once EAB arrives, it will threaten these trees and could lead to major canopy loss—impacting wildlife, stream health and neighborhood shade.
EAB cannot be eradicated, which is why preventing the arrival of EAB and slowing its spread throughout the city is crucial. With the EAB Response Plan, the City of Portland is working proactively to lessen the impact of this pest on the community.
City Forester Jenn Cairo said diversifying Portland’s canopy is integral in preparing for invasive pests such as EAB. “This is why we actively push for diverse species when we plant and promote tree planting,” says Cairo. “So that when a disease or pest attacks one species, it causes less harm to the canopy as a whole.”
PP&R is currently treating healthy ash trees in City parks with insecticide to prevent infestation. Additionally, new permit rules allow residents to treat street trees or remove and replace small ash trees (under six inches in diameter) with free permits. PP&R recommends talking to a certified arborist about treatment or removal. Tree care providers should be familiar with EAB symptoms and how to dispose of ash wood responsibly.
EAB primarily spreads when humans move or transport infested wood, especially firewood. To help protect our urban forest PP&R recommends buying firewood locally—don’t move it from other areas. You can also help by learning to identify ash trees and signs of EAB. If you suspect EAB is present or see unhealthy ash trees, those can be reported to the Oregon Invasive Species Hotline. The city has posted a document created by Oregon State University Extension Service with identification and reporting information in English and Spanish at portland.gov/trees/documents/how-identify-eab/download.
Photo by David Cappaert Michigan State University, Bugwood.org; CC BY-NC 3.0.
