Ash Tree Decline

Home Grown  by Keith Reed
If you are a regular reader of landscape plant related news from other parts of the country, the following comes as no surprise. Ash trees in the eastern United States are being devastated (i.e. virtually wiped out) by the Emerald Ash borer (EAB). The EAB was introduced to this country in the Detroit area in the 1990’s and has spread rapidly over the last 20 years.

Travelers in the eastern part of the U.S. over the last decade (including Oklahoma) may have noticed purple triangular boxes hanging in an occasional tree, especially in heavily wooded areas. These are EAB traps designed and placed to monitor the spread of this pest. The bad news is as of last fall, the EAB has been captured in eastern Oklahoma. All indications are this pest will quickly spread around the state just as it has been doing across the rest of the country.

The good news is that, for the most part, few of us in Payne County have a large number of ash trees. There are a couple of reasons for this. Oklahoma is on the western limit for the natural range of this tree. Also, in addition to the EAB, there are already a number of native tree borers that attack ash trees in our area, limiting its widespread adoption as a landscape tree. If you walk outside after reading this and see holes in your ash trees, please do not assume they are from the Emerald ash borer.

If you do have high value ash trees on your property, there is a small chance you might be able to protect your tree against this pest. However, please do not discount the emphasis placed on small chance. There are only a couple of insecticides labeled for control of this insect and even those offer limited protection. Indiscriminate applications of insecticides “just in case” will not be helpful, and may actually do more harm than good by killing beneficial insects.

OSU has recently released two helpful documents on this pest:
L-443 Signs and Symptoms of Emerald Ash Borer (only available as PDF) and L-461 Native Woodborers and Emerald Ash Borer Look-alikes (Mobile/PDF). These are also available in the Payne County Extension Office.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

Oklahoma State University, in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal laws and regulations, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any of its policies

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