The USDA recently confirmed the presence of emerald ash borer in Oregon. EAB for short, this invasive wood-boring beetle infests and kills ash trees. The beetles lay eggs in the bark crevices of trees. After hatching, larvae bore through into the tree where they feed. Their feeding and burrowing activity disrupts the flow of water and nutrients. As a result, infested trees begin to decline.
Emerald Ash Borer Spreading Steadily
EAB was first identified in the U.S. in 2002 in southeastern Michigan in 2002. The insect is native to Asia and most likely arrived on wooden shipping materials. Since its arrival, the pest has continued to extend its range to geographic regions that have ash trees. Emerald ash borer has killed millions of ash trees in North America.
In July 2022, the pest was confirmed in the Portland metro region, specifically Forest Grove, Oregon in Washington County. Confirmation from dead or dying trees usually indicates that the pest has actually been present for over a year. In this case, the Oregon Department of Agriculture estimates that EAB has likely been present for at least three to five years.
Protecting Ash Trees in Oregon
All ash species are at risk of infestation, including the Oregon ash (Fraxinus latifolia) as well as many other species planted as shade or street trees throughout the Pacific Northwest.
EAB is a highly destructive tree pest. Trees can succumb to infestation in just a few years. The insects prefer to lay eggs in the upper trunk and often go unnoticed. The canopy of the tree often yellows and begins thinning. D-shaped exit holes in the trunk indicate boring insects beneath the bark. Woodpecker activity can also signal the presence of larvae.
For ash trees in the planted landscape, highly effective treatment options are available. Taking protective measures, before the beetle arrives in the area, is critical. Once decline of the tree is obvious, it may be too late to save the tree; too much internal 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.
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