Emerald Ash Borer
Emerald ash borer is a beetle native to Asia that feeds on species of ash trees. EAB females lay eggs in crevices in the ash bark and the larvae bore into the tree to feed on the vital tissue that transports nutrients and water through the trees vascular system. The larvae grow and emerge as adults in 1-2 years to repeat the cycle all over again. First identified in Michigan in 2002, the EAB infestation continues to spread, threatening the entire North American ash population. The death of American ash trees from EAB decreases the diversity of America’s woodlands, shrinks the nation’s tree canopy, and poses risks to public safety and property, as brittle branches can fall in public or residential areas. The epidemic has destroyed approximately 8 billion ash trees in the United States.
EAB was first discovered in Tennessee in 2010. Davidson County was added to the list of invaded regions in 2014. According to the USDA Forest Service and the Tennessee Division of Forestry, it is estimated that 271 million Ash trees are at risk of EAB in TN alone. EAB is now in over 34 counties and several of those are currently under quarantine. This involves heavy monitoring of wood movement (firewood and processed wood). In another effort to help combat the threat of EAB, 1000s of traps are set out each year by the consortium made up of the USDA Animal and Plant Health Inspection Service, Tennessee Department of Agriculture, Tennessee Department of Environment and Conservation, and the University of Tennessee. The traps are triangular, purple and look like box kites. Other efforts to stem the spread of EAB include chemical pesticide treatment injected into the tree or the earth around its roots.
For more information related to EAB in Nashville: https://www.nashvilletreefoundation.org/emerald-ash-borer-in-nashville
For more information related to EAB in Tennessee: http://protecttnforests.org/emerald_ash_borer.html
Among Cheekwood’s 55-acre estate, there are 241 accessioned Ash trees. These native ash trees are more than horticultural specimen, they are part of our collection as a Botanical Garden, historic site, and museum. If destroyed, the vacancy of these trees will leave a large void.
In 2018, Cheekwood established the Emerald Ash Borer Response Program. The vision for this program is to make Cheekwood a preserve for native ash trees and a community leader in response to the emerald ash borer epidemic. The program’s main objectives are to:
- Manage and protect a large population of native ash trees on the Cheekwood property for future generations to observe, study, and enjoy;
- Celebrate the species as an important American hardwood worthy of preservation; and
- Educate the community about the species and proper management in response to the emerald ash borer (EAB) epidemic.
We endeavor to treat all preeminent ash trees at Cheekwood designated as historic or imperative to the gardens and mature tree canopy. Other considerations when selecting trees for treatment include safety people and property (risk if tree/limbs were to fall), general health of the tree, species diversity within portions of the garden, and location. Occasionally, a specimen is past the point of treatment, being too weak to transport the systemic insecticide up from its vascular system to the canopy.
We began treating for EAB in 2016 with a quantity of 10 trees. That number was increased to 33 in 2017 and, in 2018 and with the support of Piedmont Natural Gas, 47 ash trees were treated. We have selected 149 ash trees for treatment in 2019! We plan to continue this annual process, increasing the number of trees to protect each year until all preeminent ash trees at Cheekwood are treated. Treatment must be administered every 1-3 years for each tree. Over time, the treatment frequency can be decreased as the treatment begins to build up the tree’s immunity.
We are working to assist local efforts to address the EAB infestation through partnerships and community education. We collaborate with the Metro Government of Nashville and Davidson County and the Metro Nashville Tree Advisory Committee to share resources, knowledge, and expertise. Several Cheekwood staff members serve on Metro Tree Advisory Committee’s Speaker’s Bureau for public speaking engagements to educate the community.
How You Can Help
Give to Cheekwood’s Emerald Ash Borer Response Program:
You can support Cheekwood’s efforts to save its historic ash trees for the benefit of future generations. On the donation page, simply type “For the EAB Response Program” in the comments.
Help control the spread of EAB in our region:
- Refrain from transporting firewood under any circumstances as this is one of the most known ways that the beetle travels.
- Exercise Proper Tree Health Management. Keep trees well-watered and mulched, pruning when necessary.
- Inspect your Ash Trees Annually for early detection by first knowing how to identify an ash (see below) Summer is the best time to inspect, as the trees are completely leafed out. This is also the time of year for peak egg hatch and larval establishment. Call a reputable and professional arborist if you suspect EAB.
Identifying Ash Tree Species and Emerald Ash Borer
The ash tree (Fraxinus) is a member of the olive family, Oleaceae. A total of 65 species exist in North America, Europe and Asia. It is an attractive and tough hardwood that is used to make furniture, tools, oars, and baseball bats.
The three species of ash mostly commonly found in Middle Tennessee are white ash (Fraxinus Americana), green ash (Fraxinus Pennsylvanica) and blue ash (Fraxinus Quadrangulata). These are all native species. White and green ash are frequently planted in the Nashville area, while blue ash is found growing wild in our limestone soil.
Identifying the ash tree is not difficult. The leaves are dark green, opposite, pinnately compound with 5-11 ovate to ovate lanceolate leaflets at 8 – 15” long. Each leaflet is acute to acuminate at the apex and tapered at the base with remote serrations. Fall color ranges from yellow to purple. The bark is ash gray to gray/brown with diamond-shaped sections interlaced with ridges. Ash trees can grow to be very tall, with the average height being between 50-80 feet.
For an ash tree identification key: http://www.emeraldashborer.info/documents/E-2892Ash1.pdf
Signs of infestation:
- Dieback and crown thinning
- Limb death and upper leaf loss
- Excessive & active woodpecker damage (often a first symptom of early detection as this ensures that larvae are present)
- Leafy shoots emerging from the main trunk or large branches (i.e., epicormic shoots)
- Vertical bark splitting (can sometimes reveal larval
- D-shaped exit holes in the bark
- Serpentine galleries and frass (powdery wood refuse) filled tunnels beneath the bark.
- Rigid front wings meet in a straight line down the middle of the back
- Adults are dark metallic green and are the size of a small paperclip.
- Larvae are white, legless and relatively flat. They have nested bell-shaped body segments.
The Emerald Ash Borer Response Program at Cheekwood is supported by