Few things will change a landscape as quickly as an invasive tree pest or disease.
Chestnut blight essentially eliminated the American chestnut (Castanea dentata), Dutch elm disease transformed urban forests across the country, and hemlock woolly adelgid is currently devastating eastern hemlocks (Tsuga canadensis).
But there’s also an insect that threatens trees right here in Tennessee. Called the emerald ash borer (EAB), it has already killed hundreds of millions of ash trees across much of the eastern U.S.
But there are things you can do to protect your trees from this pest. We’ll explain everything you need to know below.
Getting to Know the Emerald Ash Borer
The emerald ash borer (Agrilus planipennis) is a small beetle that’s native to Asia.
It rarely causes significant problems in its native range, as its populations are largely kept in check by native parasites and predators. Additionally, the ash trees its evolved alongside have developed some natural defenses against the insect.
But that’s not the case in the U.S. Without many naturally occurring predators and plenty of defenseless ash trees to support its population, the pest kills virtually every unprotected ash it infests.
In actuality, it’s not the adult beetle that causes the problem. The adults do feed on ash tree foliage, but this only causes a negligible amount of damage. Instead, it’s the larvae, which develop under the bark of the tree, that causes harm while feeding on the tree’s vascular tissue.
This effectively prevents the tree from transporting water and sugars up and down the trunk and branches, which leads to wilting, crown dieback, and eventually death.
Having established itself throughout Tennessee, EAB is a serious threat, making proactive monitoring and treatment especially important for homeowners with mature ash trees.
Trees That Are and Are Not Vulnerable to the Emerald Ash Borer
One of the reasons EAB has been so destructive is that it attacks nearly every species of true ash (Fraxinus) found in North America. While some ash species may decline more slowly than others, untreated trees are almost always killed once an infestation becomes established.
In Middle Tennessee, the ash species most likely to be affected include:
- White Ash (Fraxinus americana): Once widely planted as a shade tree, white ash is highly susceptible to EAB and is rarely able to survive without treatment.
- Green Ash (Fraxinus pennsylvanica): Common in parks, neighborhoods, and along streams, green ash is one of the species most frequently killed by EAB.
- Blue Ash (Fraxinus quadrangulata): The blue ash is less common than white or green ash in Tennessee, but it still vulnerable to infestation.
- Pumpkin Ash (Fraxinus profunda): Found primarily in wet bottomlands and floodplains, pumpkin ash is also susceptible to EAB.
- Carolina Ash (Fraxinus caroliniana): The Carolina ash is a small tree native to wetlands in parts of the Southeast that can also serve as a host.
It’s important to note that there are a few tree species that are native to Tennessee and contain the word “ash” in their common name that are not vulnerable to EAB. That’s because these trees are not “true” ash trees — they belong to different evolutionary lineages.
This group includes:
- Mountain Ash (Sorbus spp.): Despite the common name, mountain ash belongs to the rose family rather than the ash genus (Fraxinus), making it safe from EAB.
- Prickly Ash (Zanthoxylum spp.): A small tree or large shrub in the citrus family, the prickly ash is unrelated to true ashes and immune to EAB attacks.
- Wafer Ash (Ptelea trifoliata): Also known as hoptree, this small native tree belongs to the citrus family and is not a host for the EAB.
How to Protect Your Ash Trees from Emerald Ash Borer
Once EABs infest an ash tree, they can be difficult to detect until significant internal damage has already occurred. That’s why early detection and preventative care are so important.
If you have a mature ash tree on your property, take the following steps to help protect it:
- Monitor Your Trees for Signs of Infestation: Watch for thinning foliage, canopy dieback, D-shaped exit holes, bark splits, new sprouts emerging from the trunk, and increased woodpecker activity. Catching an infestation early can provide more treatment options and improve the likelihood of success.
- Consider Preventative Treatments: Systemic insecticides can effectively protect healthy or lightly infested ash trees when applied before extensive damage occurs. Treatment schedules vary depending on the product used, so it’s important to work with a qualified tree care professional.
- Maintain Tree Health: While healthy trees are still susceptible to emerald ash borer, proper watering during drought, mulching, and avoiding unnecessary injuries can help reduce additional stress and support the tree’s response to treatment.
- Remove Hazardous Trees Promptly: Untreated ash trees almost always decline once EABs become established. Removing dead or severely declining trees can reduce safety risks and help prevent costly property damage from falling limbs or whole-tree failure.
Common Emerald Ash Borer Questions
Because EABs have killed millions of ash trees across North America, many homeowners and property managers have questions about the insects and the risks to their trees. Here are answers to some of the questions we hear most often.
What is the emerald ash borer?
The emerald ash borer is an invasive beetle native to Asia. Its larvae feed beneath the bark of ash trees, disrupting the tissues that transport water and nutrients. Left untreated, most infested ash trees die within a few years.
Which trees are vulnerable to emerald ash borers?
True ash trees (Fraxinus spp.) are the beetle’s primary hosts. In Tennessee, this includes white ash, green ash, blue ash, pumpkin ash, and Carolina ash.
How can I tell if my ash tree is infested?
Common signs of EAB infestation include thinning foliage, dead branches in the upper canopy, excessive sprouting along the trunk, bark splits, D-shaped exit holes, increased woodpecker activity, and winding galleries beneath the bark. Because these symptoms can resemble other tree problems, a professional inspection is the best way to confirm an infestation.
Can an emerald ash borer infestation be treated?
Yes, but timing is critical. Preventative and early-intervention systemic insecticide treatments can successfully protect many healthy or lightly infested ash trees. Trees with severe canopy decline are often too heavily damaged to save.
Should I remove my ash tree if emerald ash borers are in my area?
Not necessarily. Healthy, structurally sound ash trees can often be preserved with timely treatment. Removal is generally recommended only when a tree is dead, poses an unacceptable risk, or has declined beyond the point where treatment is likely to succeed.
How quickly do emerald ash borers kill ash trees?
Many untreated ash trees decline over two to four years after becoming infested, although heavily stressed trees may deteriorate more quickly.
Are emerald ash borers active year-round?
EABs are present throughout the year, but their activity changes with the seasons. Adults typically emerge and lay eggs from late spring through early summer, while the larvae spend the rest of the year feeding beneath the bark.
Give Your Ash Trees the Best Chance to Survive
Healthy ash trees add beauty, shade, and value to your property. But without proactive care, emerald ash borers can destroy them in just a few years. Whether you need a professional diagnosis, preventative treatment, or safe removal of a declining tree, AKA Tree Service is here to help.
Our ISA-certified arborists provide honest recommendations and effective solutions tailored to your property’s needs. Contact us today to schedule an inspection and take the first step toward protecting your trees.
Sources and References
- University of Tennessee Extension, Marion County – “A New Pest for Marion County”
County extension factsheet introducing emerald ash borer as a new invasive threat to Marion County’s ash trees.
https://marion.tennessee.edu/wp-content/uploads/sites/55/2020/01/A-New-Pest-for-Marion-County.pdf - Tennessee Department of Agriculture, Division of Forestry – “Emerald Ash Borer”
State forestry program page on Agrilus planipennis identification, spread, and management guidance for Tennessee landowners.
https://www.tn.gov/protecttnforests/insects/emerald-ash-borer.html - City of Nashville, Metro Water Services (Stormwater Division) – “Emerald Ash Borer”
Municipal stormwater/tree program page addressing emerald ash borer impacts on Nashville’s urban tree canopy.
https://www.nashville.gov/departments/water/stormwater/tree-information/emerald-ash-borer - Nashville Tree Foundation – “Emerald Ash Borer”
Local nonprofit page on emerald ash borer’s threat to Nashville’s ash trees and community tree-canopy preservation efforts.
https://nashvilletreefoundation.org/emerald-ash-borer/
