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Ash Trees in Danger From Borer Beetle

By Clackamas Soil and Water

Ash Trees in Danger From Borer Beetle

The native Oregon ash tree has been widely used in urban areas and streamside restoration projects throughout Western Oregon. Unfortunately, this popular tree is currently at risk of attack by the Emerald Ash Borer (EAB). The EAB is a beetle native to parts of Asia but in 2002 was detected in parts of Michigan and Canada. Until recently, the beetle’s Westernmost detection was in Colorado.

As you have probably heard, EAB has made it to Oregon. Current information indicates that the infestation is isolated to the Forest Grove area in Washington County. The Oregon Department of Agriculture (ODA) is working hard to contain the infestation. In June they released four types of parasitic wasps that are natural enemies of the EAB. ODA also established over 100 trap trees surrounding the area that will help track which direction spread may occur. Many organizations, such as the Clackamas Soil and Water Conservation District, have set traps to help monitor any movement of the beetle.

Why is this important? The shade provided by Oregon native ash trees helps to keep the sun from heating stream water. Ash trees also provide bank stability, reducing the possibility of erosion. Unfortunately, this beetle will attack all ash species with death rates of up to 99%. The expected die-off in Oregon has experts worried about the negative impacts on water quality and wildlife habitat. To learn more about replacement trees for Oregon ash see this article, “Alternative to Ash in Western Oregon” by George Kral and David G. Shaw, OSU Extension Forest Health Specialist, or search for “Alternatives to Ash in Western Oregon” on the internet.

In addition to problems in nature, economic loss is expected from this insect attack. Ash trees are a popular tree in nursery production. Any quarantine caused by this insect will affect the nursery industry in Oregon. Losses in the millions of dollars would pose a hardship for our local nursery operations.
Cities and homeowners will also share in the financial loss. Ash used for street trees provides urban shade, cleans the air, offers urban wildlife habitat and human health benefits in addition to improving property values. The cost of tree removal for public safety and the replacement of trees will be a big hit in the pocketbook for cities and homeowners.

How can you help? Watch for signs of EAB in ash trees and report it. Look for: significant crown dieback in heavily infested trees (starts in the top third of the crown); sucker shoots emerging from the trunk or base of the tree; woodpecker activity that gives the bark a distinct mottled appearance; D-shaped holes in the bark about 3 mm (0.1 inch) in diameter; splitting bark; S-shaped galleries underneath the bark; adults visible in summer.

Find this and information on how to report an infestation in the bilingual brochure from OSU Extension, “Oregon Forest Pest Detector Pest Watch: EAB,” or do an internet search for “Pest Watch EAB.”
Another useful publication is a guide developed by ODA to help identify EAB look-a-like species. or search on the internet for Emerald Ash Borer ODA.

Just a final reminder, Do Not Move Firewood. Invasive pests such as Emerald Ash Borer and pine bark beetle can spread when infested wood is transported to other areas.

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