Emerald Ash Borer

The Forest Board has reviewed the recommendations on Emerald Ash Borer treatment over the past two years and has reviewed the Park ashes with several experienced Certified Arborists. The first 10 trees out of 30 were treated in 2010 and 12 trees will be treated in 2013, with retreatment in 2015.

Effective treatments for Emerald Ash Borer depend on size of the tree, and almost all of the ashes in Audubon Park are substantial trees (larger than 6-8 inches in diameter at 4.5 foot from the base of the tree). Mature trees require injection by an experienced Certified Arborists and Emamectin benzoate appears to be the most effective agent. All the people listed below are using Emamectin.

Treatment currently costs about $10 per inch of diameter, so a tree of 30 inch DBH is approximately $300 to treat. For early prevention, treatment should occur in mid-May to mid-June, and can be stretched to every three years. When we identify an active epidemic in Audubon Park, it will be safer to treat at two year intervals, and then resume three year treatments after most trees are removed in our area. Recommendations are that the tree be treated for its entire life-span.

In general, you should not treat a damaged or compromised tree, particularly a tree with major wounds or areas of visible or developing rot. Your arborist can evaluate whether the tree is worth treating. If you do remove an ash, please ask that it be inspected careful for whether EAB contributed to its decline. Let the Forest Board know if you identify EAB in your tree.

You are making an investment in treating your tree, and it can difficult to assess and weigh the costs of long-term treatment compared to the cost of removal of the tree in the next few years. Sometimes it will be better to remove the tree, and get replanting done. A certified competent up-to-date and well-trained professional arborist can help you with this decision. You will be spending substantial amounts in treating your tree, and make sure you choose an honest established provider. There are also many online resources that look at the cost-benefit of various strategies. But only you know the tree and the benefits it provides you and what it is worth to retain it.

Several experienced people already have been treating ashes with injection of Emamectin benzoate in Audubon Park. For your convenience, we have listed their companies and names, with contact information. Many other reputable tree companies have developed a Plant Health division in their company in anticipation of the impact of EAB in Louisville. Please bring them to the attention of the Forest Board so we can update the list of providers if you are satisfied with their professional qualifications and work.

Some current providers of Emamectin benzoate injections

Arbor Worx, Joe Clayton, 502-491-1304; 502-817-3183.
Natural Resources and Property Management, LLC, Gregory Stephens, 502-896-6369; cell: 502- 435-2497, email: greg.stephens50@att.net.
Limbwalker Tree Services, Inc., 502-634-0400

(The excerpt below is from “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer” by Herms, McCullough, Smitley, Sadof, Williamson, and Nixon.)

Trunk-Injected Systemic Insecticides

Emamectin benzoate • In several intensive studies conducted by MSU and OSU researchers, a single injection of emamectin benzoate in mid-May or early June provided excellent control of EAB for at least two years, even under high pest pressure. For example, in a highly-replicated study conducted on trees ranging in size from 5-to 20-inch DBH at three sites in Michigan, untreated trees had an average of 68 to 132 EAB larvae per m2 of bark surface, which represents high pest pressure. In contrast, trees treated with emamectin benzoate had, on average, only 0.2 larvae per m2, a reduction of > 99 percent. When additional trees were felled and debarked two years after the emamectin benzoate injection, there were still virtually no larvae in the treated trees, while adjacent, untreated trees at the same sites had hundreds of larvae.

In two OSU studies conducted in Toledo with street trees ranging in size from 15 to 25-inch DBH, a single application of emamectin benzoate also provided excellent control for two years. There was no sign of canopy decline in treated trees and very few emergence holes, while the canopies of adjacent, untreated trees exhibited severe decline and extremely high numbers of emergence holes.

One study suggests that a single injection of emamectin benzoate may even control EAB for three years. Additional studies to further evaluate the long-term effectiveness of emamectin benzoate are underway. To date, this is the only product that controls EAB for more than one year with a single application. In addition, in side-by-side comparisons with other systemic products (neonicotinoids), emamectin benzoate was more effective.

Information Sources

There is excellent information about Emerald Ash Borer on the University of Kentucky Extension Service website and at the Emerald Ash Borer Homeowner information site http://www.emeraldashborer.info/homeownerinfo.cfm).

One comprehensive and widely-cited article about various treatments is entitled “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer” by Herms, McCullough, Smitley, Sadof, Williamson, and Nixon (16 pages). It is available as .pdf file on the Tree Committee website at www.treecommittee-apky.org and on various websites.