Emerald Ash Borer: Nashville’s Ash Trees Face ‘Massive’ Die-Off

One of the greatest threats to the tree canopy in Nashville is the Emerald Ash Borer (EAB), an insect imported from Asia that is decimating Ash trees in Middle Tennessee and many other parts of the country. This deadly invader was first detected in the U.S. in Michigan in 2002, first found in Tennessee at a truck stop in Knoxville in 2010 and first detected in Davidson County in 2014.

Though the march of the Emerald Ash Borer is ongoing and unstoppable, there are actions we can take as homeowners and landowners to help manage this insect epidemic and mitigate the toll on our Ash trees. Here, we’ll provide an update on where things stand with EAB in Nashville and Middle Tennessee and recap the steps you can take to keep some Ash trees healthy.

Let’s start with the bad news: EAB is having a devastating effect on Nashville's Ash trees. “There are some apparently healthy Ash trees in Davidson County. However, at this point, 8 years after initial detection, most Ash trees that are untreated will be to some extent infested even if that is not yet obvious,” according to Steve Powell, state entomologist with the Tennessee Department of Agriculture. “Over the next 2-3 years, there will be Ash decline/death on a massive scale in the Nashville area for untreated Ash trees. If a homeowner has Ash that they want to keep, treat [as soon as possible] if it’s not too late, otherwise the tree is at a high risk of mortality within the next few years.”

The Emerald Ash Borer is an Asian beetle about a half-inch long with bright green metallic wings. It kills all species of Ash trees (including White, Green and Blue Ash) as its larvae burrow beneath the bark, leaving tunnels that prevent the tree from drawing nutrients up from its roots.

The Metro Tree Advisory Committee has estimated that 6% of the countywide tree canopy is composed of Ash trees. In the Warner Parks, the largest park in Nashville, an estimated 15-16% of the total canopy is Ash. As the EAB infestation continues, most of these trees will be lost. Statewide, the potential loss is far greater -- there are an estimated 271 million Ash trees in Tennessee, valued at $11 billion, according to the U.S. Forest Service and the Tennessee Division of Forestry.

Ash trees are found on private and public property throughout Nashville, including schools, government buildings and parks. Metro Government has been conducting an inventory of Ash trees on public land, marking them with a blue dot or blaze. The infected Ash trees that present the greatest safety risk will be removed.

Treating EAB

The situation with EAB is admittedly dire, but it’s not too late to take action if you have Ash trees on your property. Experts have these recommendations for treatment:

• The best time to treat for EAB is before an infestation occurs. These insects kill trees quickly — within 1-2 years for smaller trees and 3-4 years for larger trees. If your tree is already infested and has dieback and a thinning canopy, it is probably too late to save it.

• The best season to treat your Ash trees is spring, though some of the insecticides approved for EAB also work in fall.

• EAB treatment is costly and ongoing — usually annually or every two years. For that reason, it’s best to conduct an inventory of the Ash trees on your property and focus your efforts on the trees you most want to save.

• If possible, hire an arborist to assess your Ash trees and treat them. Some homeowners choose to DIY the process — see details on insecticides below. Trees larger than 15 inches in diameter are more appropriate for professional treatment.

• If your Ash tree is already infested with EAB and can’t be treated, have it cut down before it dies and becomes too brittle.

The most important thing to remember about EAB and your Ash trees is that this epidemic is moving fast. If you’ve been thinking about treating your Ash trees, now is the time to decide and take action.

RESOURCES

Maps and charts at EmeraldAshBorer.info show which counties in Middle Tennessee (and elsewhere) have detected EAB.

Purdue University has published a helpful Decision Guide for homeowners who are trying to decide whether to treat their ash trees.

If you decide to treat your Ash trees yourself rather than hiring a professional, this bulletin provides information on insecticides intended for sale to homeowners.

For those whose trees are already infected with EAB, Metro Public Works and the Metro Tree Advisory Committee outline the responsibilities of homeowners in this brochure.

More info on EAB in Davidson County is offered here, including how to identify whether your tree is an Ash and how to spot signs of EAB infestation.

Keeping a close eye on all your trees can help to prevent small problems from turning into big ones. Subscribe to our newsletter to receive regular updates on tree care and tree policies in Nashville.