Emerald Ash Borer

The Emerald Ash Borer (EAB) is an exotic wood boring insect originally from Asia. It was first discovered on our continent in Michigan in 2002 and since then has been munching its way across the country. The first EAB in Franklin County was found in a trap in 2015, but it has taken until this year for us to find evidence of them on the University of the South campus.

If no action is taken, EAB will kill all ash trees it comes in contact with. There are chemical treatment options for individual trees, but they can only be applied by professionals and are practical only in an urban context.

If you have ash trees on your leasehold, now is a great time to take a look at their health. Here is a good introductory video but there are many more good references online for both identification of ash trees and signs of infestation. Sewanee student members of the Forestry Club are willing to help leaseholders with ash and EAB identification. If interested, please email them at forestryclub.sewanee@gmail.com.

At this point, we are early in our infestation. The most common symptoms seen around campus are thinning crowns and an increasing number of dead branches. A good example of these symptoms can be found in an ash tree on Georgia Avenue in front of the Bishop's Common. While there are not yet any of the characteristic D-shaped exit holes in the trunk bark, limbs are beginning to die in several areas of the crown, and if you were to climb the tree you would see these limbs have those characteristic holes. As the infestation grows in the tree, the EAB will make its way to the trunk.

If you have trees on your leasehold that you would like to protect, it is important to act soon. Once a tree has lost more than 30% of its canopy, it may not be possible to save it. We are expecting exponential growth of EAB on the Domain over the next couple of years and experience from other areas of infestation lead us to believe that most ash trees on the Domain will be dead in 10 years. Once most of the ash trees are dead, the EAB population will crash and maintenance of trees chemically treated can become less intense.

On the central campus, Facilities Management, Domain Management, and Forestry faculty are working together to identify which central campus trees may be appropriate to chemically treat. Spring treatment of trees is most effective, and we hope to begin treatment next spring. Unfortunately, many of the ash trees on campus will also be removed. Because of the way EAB kills ash trees, affected trees quickly become brittle,making them both a hazard while standing and dangerous to remove. For this reason, you may see ash trees from central campus removed before they are dead.

Beyond the central campus, ash makes up only about 17% of the Domain forest. Unfortunately, the ash is not evenly distributed and there are some areas on the side of the mountain where ash is one of the dominant canopy trees. We are currently working with the Landscape Analysis Lab to identify what areas of the Domain may be most affected by this new pest.

Once areas of high concentrations of ash are identified, one of several things may happen. For most of the Domain, the ash will die without intervention and provide opportunities for students and faculty to observe and measure how the forest ecosystem adapts. We are also in conversation with the United States Department of Agriculture (USDA) about being a possible site for biological control experimentation. The USDA has identified and approved for use four species of parasitic wasp that prey only on the EAB. They are interested in using some stands on the Domain to release these wasps and monitor for success. These biological controls will not save the older trees, but seem to offer some hope of saving some of the genetic heritage of ash trees, protecting young trees from infestation and saving the species from removal from the landscape. The University will also try to preemptively remove some ash in locations where it is easily accessible and financially viable.

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