Greenspace News & Events
By Kelsi Stubblefield Lewis, intern with the Division of Sustainability, Fall 2018
It’s a metallic green beetle no bigger than a penny, and while it may not look intimidating at first, this tiny insect could cause serious harm to Nashville trees.
The Emerald Ash Borer is a small, invasive Asian beetle whose larvae burrow into and feed on the inner bark of ash trees. Likely originating in Asia and transported to the United States via wood packing material, it is estimated that Emerald Ash Borers have been present in Davidson County since 2014 and in Tennessee since 2010. [i] [ii]
“Nashville has many beautiful native ash trees in parks, on school grounds, along city streets and in private yards.” Nashville City Horticulturist, Jennifer Smith, said. “Sadly, the Emerald Ash Borer, an invasive pest, will kill all of them by 2025-2030 unless the trees are treated. No ash tree is immune to the devastating effects of this insect which is now in Davidson County. The progress of the infestation and resulting tree death is swift.”
Ash Trees at Cheekwood Botanical Gardens. Credit: Patricia Miller
In Tennessee, Smith explained, the typical life cycle of an Emerald Ash Borer looks like this:
In May or June, the adult Emerald Ash Borer beetles fly in the tree tops for about two weeks looking for mates, sometimes up to 18 miles from where they originally hatched. After mating, the female beetle lays 40-70 eggs on the bark of the ash tree. When the eggs hatch in two to three weeks, the tiny larvae bore into the tree layers just below the bark to feed. When eating the wood under the bark, the larvae leave behind distinctive S-shaped tunnels. Larvae continue development into early fall, getting larger, going through four stages before the pupa stage. One to two weeks into the spring season, a new generation of adult beetles emerges from the tree through small D-shaped holes, ready to begin the cycle again.
The effects of the larvae’s feeding are devastating. Ash trees infested with Emerald Ash Borers need to be treated as quickly as possible, as infested trees can die as soon as one to three years after symptoms occur.
Is my tree infested?
According to the Metropolitan Nashville Public Works and The Metro Tree Advisory Committee, the following are signs of Emerald Ash Borer infestation:
A declining top (crown) with leaf loss and dying branches is often the first visible symptom.
Distinctive pencil sized D-shaped exit holes in the bark. Other native borers leave more roundly shaped exit holes.
When the bark is peeled back, larvae are found feeding underneath or have left s-shaped serpentine galleries.
Apparent “blonding” on the outside of the tree from woodpeckers stripping off bark in attempt to feed on the larva inside.
Small sprouts growing from the tree roots or trunk. [ii]
Smith stresses that if you find out that you have an ash tree, now is the time to take action. Don’t wait until an infestation becomes apparent. Often by the time an ash tree has lost 30% of its crown, treatment may no longer be effective. “Be sure to follow recommendations on how to hire an arborist who can determine the health of your tree, offer removal alternatives, and treatment options,” Smith advises, “the sooner decisions are made about how to deal with your tree, the less expense will be incurred.”
If you discover that a neighbor has an ash tree, or that their ash tree is infested, let them know as soon as possible. They may be unaware of the Emerald Ash Borer epidemic. If you suspect an ash tree in the city right-of-way to be infested, call hubNashville at 615-862-5000 or 311 to report it.
When asked who should be concerned about the Emerald Ash Borer Epidemic, Smith’s answer was simple: everyone. “Nashville’s trees are very important to us,” Smith said, “trees improve air quality, conserve energy and reduce energy costs, reduce storm water runoff, provide wildlife habitat, and many other benefits. They add natural character to Nashville and give neighborhoods a sense of identity. It is estimated that ash trees make up approximately 10% of our urban forest canopy. A loss of 10% of our trees will affect all of us.”
Jennifer Smith had one final piece of advice to offer in response to the epidemic: “Plant trees! Our valuable and loved city’s forest will need help in recovering from the Emerald Ash Borer epidemic.”
The Landscape and Green Infrastructure Manager at the Department of General Services, Treff Alexander, spoke about how his team has been heeding Smith’s advice and planting trees to combat the Emerald Ash Borer epidemic. Alexander stated that there were approximately 12-20 ash trees on the city properties managed by the Department of General Services, and all but one have been removed. Some of the trees were displaying telltale signs of infestation, Alexander said, such as sprouts at the base and rot, so the trees were removed as a safety precaution, with the goal of preventing them from becoming a fall hazard. Plans are in place to replant different species of trees in place of the removed ash trees.
To learn more about tree planting, the Emerald Ash Borer epidemic, and how you can protect ash trees visit trees.nashville.gov.
The EAB Speaker’s Bureau, presented by the Metro Tree Advisory Committee, offers free informational presentations about the Emerald Ash Borer epidemic for organizations, workplaces, or places of worship. To schedule a free EAB presentation, register at trees.nashville.gov or contact Metro Horticulturist, Jennifer Smith at 615-862-8708.
A free, public talk about the Emerald Ash Borer is being held October 18, register now at https://crc.kindful.com/register/river-talk-october-18-2018.