The emerald ash borer (EAB) is an invasive wood-boring beetle from Asia that infests and kills ash trees (Fraxinus spp.) native to North America. Discovered in southeastern Michigan in 2002, it was most likely introduced on wooden shipping materials. EAB has steadily spread across the United States, leaving millions of dead ash trees in its wake. The entire natural range of our native North American ash trees is at risk.
EAB was detected in Oregon in 2022 and its spread is threatening both urban and natural ash populations. The Oregon ash (Fraxinus latifolia) is the only ash species native to the Pacific Northwest. It grows in moist to wet soils and plays a vital role in riparian ecosystems, helping to cool waterways, filter pollutants, and stabilize soil.
EAB larvae feed under the tree’s bark, cutting off nutrient and water flow, which can happen in as quickly as a few years and will lead to death of the tree. Thankfully for ash trees in the planted landscape, highly effective insecticide options (including organic!) are available. Taking proactive, protective measures before the beetle arrives in the area is vital because once decline of the tree is obvious, it is often too late to save the tree; too much damage has already occurred. If a tree is not to be treated, it should be removed, given that dead ash becomes very brittle and will begin dropping branches, becoming a safety issue.
