The Emerald Ash Borer in Nashville

The emerald ash borer (EAB) has had a serious effect on Nashville’s ash trees over the last several years since the invasive beetle was first spotted in Davidson County in 2014. This year, in 2023, it has become more apparent how devastating that effect has been. Although some precautions can be taken to manage surviving trees, the emerald ash borer’s damage is real and ongoing.

2023 EAB Update

Last year, we gave an update expecting that the EAB’s infestation would result in the decline and death of ash trees over the following few years. We recently checked in with Michael Davie, NTCC board member and certified master arborist at Bartlett Tree Experts, for his professional assessment of the EAB’s impact in Nashville and across the state of Tennessee. 

“It’s apparent that it’s much worse this year,” Davie told us. “It was difficult to tell how much it advanced last year because the drought caused browning and defoliation of a lot of leaves, but this spring, it became apparent how far the damage had advanced. If you drive around town or on the interstates and see big masses of dead trees, chances are they’re ash. It is widespread across middle Tennessee, the worst of it being in the west and south.” 

Emerald Ash Borer Facts

The emerald ash borer is a half-inch-long, bright green beetle that burrows into ash trees specifically to feed on the trunk’s inner tissue and nutrients. This invasive insect is originally from Asia and is thought to have been brought over through foreign trade in infected wood shipping pallets. It was first noticed in Michigan in 2002, and ever since, it has spread throughout North America, killing millions of ash trees over the years. 

When the EAB tunnels into an ash tree, it disrupts the flow of moisture and nutrients throughout the tree, damaging its tissue and preventing the tree from receiving essential sustenance. Not only do the adult beetles tunnel throughout the tree’s trunk, but they lay eggs in the tree, and the beetle’s larvae continue the cycle. Usually, a tree has between three to ten years before it dies after being infested. Like any structurally weak or dying tree, it then becomes hazardous to people and property, as it will eventually fall if not removed. An infected tree also becomes a threat to other ash trees nearby when the beetle spreads in search of another host tree. 

Identifying an Ash Tree and EAB Presence

The ash is a canopy tree that has grayish, diamond-ridged bark with groups of five to nine leaflets to a branch and samara (helicopter) seed pods. When a tree has been infested with the emerald ash borer, there are telltale signs that point to the beetle’s presence:

• D-shaped entry and exit holes on the trunk

• Unseasonal yellowing and/or browning of leaves

• Unseasonal loss of leaves

• Loss of bark

• Noticeable serpentine patterns along the trunk

• Dying branches

• Woodpecker activity (from feeding on the beetle larvae)

If any of these signs start to show up on your ash tree, a certified arborist should be contacted to evaluate the damage. They can safely treat or remove an affected tree as appropriate.

Is There Anything Being Done to Stop the Emerald Ash Borer?

Unfortunately, it seems the emerald ash borer is here to stay. It’s very challenging to deal with the insect population as a whole, which is why the best way to keep your ash tree from an EAB infestation, and thereby keep the population down, is through preventative treatment. A certified arborist can treat the healthy ashes in your yard with an application that is injected into the tree and offers one to three years of protection, depending on the treatment. 

How to Get Rid of the Emerald Ash Borer 

When a tree becomes host to the beetle, treatments can be applied that will slow the decline of the tree. This is the best option for large, mature ashes that have value to the owner. However, once the tree is infested, decline is inevitable, and the tree will eventually have to be removed. It’s best to start treatment when it’s still healthy, either before an infestation or as early as possible once the EAB is noticed.

Why Is the Emerald Ash Borer Still a Problem?

Aside from the challenge of eradicating the insect’s population, the beetle remains a problem because emerald ash borers target mature trees; not saplings. This means that as long as young ash trees are growing, they will eventually become susceptible to an infestation. Since an ash takes several years to die once the beetle takes hold, those ash trees may reseed in the meantime and establish new ash saplings. 

Another reason that the beetle poses such a problem is that the decline in the number of ash trees is a significant and ongoing loss to the canopy. Mature trees take decades to grow, and only once they reach their full height and size can they provide important and essential ecosystem services to a location. This may warrant the costs of preventative treatment on mature ash trees since tree removal may actually be more costly, both financially and in terms of lost benefits. Eventually, however, an infected ash will need to be removed, and it will take time for a new tree to mature.

When an ash tree must be removed, Michael Davie advises replacing it with a tree of another type. “Even non-native ash that are not damaged by the emerald ash borer are usually damaged by the native borers and don’t do well anyway,” he says. If you like the look of the smaller leaves of an ash, consider a honey locust, yellowwood, or Kentucky coffee tree. If those might not be right for the location, browse our wide variety of trees available through the Nashville Tree Conservation Corps’ annual tree sale to find the specimen that will be the best fit for your needs.

For regular updates on tree news, as well as information on tree care and the types of trees found around Nashville, subscribe to our newsletter. If you want to get involved with us, consider volunteering and lending a hand to supporting the local canopy! 

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.

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.