The Threat of Emerald Ash Borer
Fraxinus: Our native Ash tree
The Ash tree 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.
Photo credit: Paul Wray, Iowa State University, Bugwood.org
Emerald Ash Borer: The Enemy
It is highly suspected that the extremely damaging and invasive Emerald Ash Borer (EAB) first hit North America in the early 1990s, most likely in a shipment of Ash tree lumber from Asia. In 2002, the insect was officially identified in Detroit, Michigan. Since this date, the EAB has been responsible for approximately 8 billion Ash tree deaths in the United States, rapidly becoming a national threat by infiltrating 22 states. The borer larvae feed on bark galleries under the tree’s bark, injuring the vital phloem and xylem tissues which transport nutrients and water throughout the vascular system.
In Tennessee, the Emerald Ash Borer was first found in an infected Ash tree growing at a truck stop in Knox County. 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.
Photo Credit: Debbie Miller, USDA Forest Service, Bugwood.org
Cheekwood’s Plan of Action
Among Cheekwood’s 55-acre estate, there are 241 accessioned Ash trees. We first began treatment for EAB in 2016 with a quantity of 10 trees. The next year that number was increased to 33. For 2018, 50 ash trees have been chosen for treatment. Selecting Ash trees for treatment is heavily based on risk assessment, which considers the possible danger to people and structures if a tree, or parts of a tree, were to fall. General health, species diversity, and location also play key parts in the decision making, as well as the tree’s significance to Cheekwood’s landscape and tree canopy (which trees would cause detriment to the canopy if infected and removed accordingly).
We plan to continue this annual process, increasing the number of trees to protect each year. While inspecting trees for treatment selection, it was also noted if a tree needed to be removed. Often, a specimen is past the point of treatment, being too weak to transport the systemic insecticide up from its vascular system to the canopy. It has been concluded that if 50% or more of a tree’s canopy has been killed, it is past the threshold of being saved.
How You Can Help
Early detection can be challenging because it can take 1-3 years before trees look symptomatic. Signs of decline are due to the borer larvae feeding on tree tissue, disrupting sugar and water transport through the vascular system and effectively starving the tree.
Know what you can do to help save this important native tree that makes up a huge portion of our Tennessee woodlands.
- 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. Summer is best to ensure trees are completely leafed out. This is also the time of year for peak egg hatch and larval establishment.
- Learn to recognize Emerald Ash Borer:
- 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
- Call a reputable and professional arborist if you suspect EAB.
- Lastly, refrain from transporting firewood under any circumstance as this is one of the most known ways that the beetle travels.
The following are symptoms to look for:
- 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 galleries beneath)
Other signs of an EAB infestation:
- D-shaped exit holes in the bark.
- Serpentine galleries and frass (powdery wood refuse) filled tunnels beneath the bark.
Photo credit: Daniel Herms, The Ohio State University, Bugwood.org
Dirr, Michael A. Manual of Woody Landscape Plants. Champagne: Stipes, 2009 6th Edition.
Learn More With Us
We’ll be hosting a panel discussion about Emerald Ash Borer featuring Peter Grimaldi, VP of Gardens and Facilities at Cheekwood, as well as:
Josiah Lockard: TUFC, Panelist
Dr. Young: TSU, Panelist
Jason Oliver: TSU, Panelist
Caroline Sorenson: NTF, Panelist
Saturday, April 14
Recreation Room located in the Cheekwood Mansion
About the Panelists
Carolyn Sorenson is the executive director of the Nashville Tree Foundation, (2008-2018). She manages overall operations and staff of the non-profit that plants and preserves Nashville’s trees. Programs include the Big Old Tree Contest, Arboretum designations, education and community outreach, community tree plantings and free tree giveaways. Member of the Alliance for Community Trees, Metro Tree Advisory Committee, and Belle Meade beautification committee. Sorenson is graduate of the University of Georgia, and was raised in Greenville, SC.
De’Etra Young is an assistant professor and extension specialist in the Agricultural and Environmental Sciences Department at Tennessee State University where she has been teaching since the Spring 2013 semester. Young attended Southern University and A&M College where she majored in urban forestry, earning her B.S. degree in 2004. She was then accepted into the M.S/Ph.D. programs in forestry at Texas A&M University in College Station, TX. While at Texas A&M, she completed her Ph.D. in forestry with a concentration in spatial and hydrological sciences. De’Etra discovered her passion for teaching spatial and environmental sciences during her time at Texas A&M as a teaching assistant and participant in the Graduate Teaching Academy. She currently serves as the advisor for the Minorities in Agriculture, Natural Resources, and Related Sciences (MANRRS), Tennessee State University Chapter. She is also a member of the Metro Tree Advisory Committee and Nashville Alumnae Chapter of Delta Sigma Theta Sorority, Incorporated. Lastly, she serves as a board member of the Tennessee Urban Forestry Council.
Dr. Jason Oliver has been at the Tennessee State University Otis L. Floyd Nursery Research Center since 1997. He earned his doctorate degree in entomology from Auburn University and Master’s in entomology from the University of Tennessee. Oliver currently has a 100% research appointment at TSU focused on nursery crop insect issues. His primary research focus includes management of wood-boring insects like flatheaded borers and ambrosia beetles in nursery crops and development of certification treatments and biological controls for imported fire ant and Japanese beetle. He has past research experience with the development of new trapping techniques for invasive wood borers like emerald ash borer and walnut twig beetle.
Josiah Lockard boasts over 20 years of professional practice, and specializes in ecologically based landscape design and sustainable site development. Lockard became a ISA Certified Arborist in 2003,and is a graduate of Lipscomb University’s Institute for Sustainable Practice. Heis an award winning Landscape Designer, member of the American Society of Landscape Architects, LEED Green Associate, and serves as both Consulting Arborist, and member of the Garden Development Committee at Cheekwood Estate & Gardens. In 2011, he founded the multi-disciplined firm Josiah Lockard & Associates (JLA), where he engages in projects throughout Middle Tennessee and internationally. Combining the disciplines of Landscape Architecture, Agriculture, Sustainability and Urban Forestry, Lockard integrates natural systems into the built environment to create spaces that have apositive affect on both people and nature.