The Emerald Ash Borer (EAB) has been a growing problem all across North America since the invasive species arrived from Asia. State and national parks, arborists, nurseries, and utilities have all felt the negative impact of this pest, and KUB is no exception. The below Frequently Asked Questions will help you understand more about the EAB and the threat it poses.
Questions and Answers
What is the Emerald Ash Borer (EAB)?
It is an invasive species of beetle that is believed to have arrived in America from Asia in wood packing materials. It was identified in southeast Michigan in 2002, but it is believed the EAB arrived a decade earlier. The adult beetles are metallic green, and are about one-half inch long. The larvae are cream colored or light brown, with brown heads and a ten-segmented body.
Emerald ash borer adult feeding on an ash leaf.
Do they only attack ash trees?
While there have been some reports of the EAB attacking the white fringetree, the EAB most commonly attacks ash trees, and all types of true ash trees are at risk. Tens of millions of trees have been destroyed by this pest since it arrived.
What does an ash tree look like?
Ash trees come in many species, but are typically medium to large in size and mostly deciduous, meaning they lose their leaves seasonally. They have an opposing branch structure, where branches grow opposite of one another. Ash trees also display a compound leaf structure, meaning multiple leaflets grow from a single stem or leaf, and these also display the opposing growth pattern. There are typically 5-9 leaflets per leaf. As the tree ages, the bark changes from smooth to rough with a diamond pattern or ridges. It is important to note that the mountain ash is not a true ash, and is therefore not impacted by the EAB. This website (https://treedoctor.msu.edu/ash/ashtree_id) is a great resource for identifying ash trees.
Ash Tree Ash tree leaf
How do they kill trees?
Adult beetles eat the leaves with minimal impact to the tree, however, the danger comes from the larvae. The female beetles lay eggs in the bark, cracks, and crevices of the tree. When the eggs hatch, the larvae feed on the inner layers of the tree, creating curved hollow tunnels. When the larvae mature, they chew through the outer bark of the tree. The hollow tunnels disrupt the flow of water and nutrients through the tree to its branches and leaves, killing the tree. Once the Emerald Ash Borer enters an area, it takes as little as two years for damage to be seen, and 5-7 years for the trees to die.
How can I spot a tree that has been impacted?
Trees that have been attacked by the Emerald Ash Borer will have the following signs:
o Thinning canopy/dying branches (usually beginning at the top of the tree)
o New sprouts emerging from the bottom of the tree
o Splitting bark
o Zig-zag or curving tunnels under the bark
o D-shaped holes approximately 1/8th inch in diameter (this unique hole is left when the adult EAB leaves the tree)
o Increased woodpecker activity (woodpeckers feed on the larvae when possible)
D-shaped exit holes of the adult EAB Ash tree show symptoms of EAB
and the zig-zag/curved borer gallery
Close up of D-shaped exit hole Dead Ash Trees
Is this a problem for KUB and other utilities?
Yes, trees that have been compromised by the Emerald Ash Borer are dead and weakened, meaning the limbs and the tree itself are more susceptible to falling into power lines.
In Tennessee, the first known tree impacted by the EAB was found in Knoxville near I-40 in July, 2010. While we are fortunate that ash trees do not make up the majority of the urban tree canopy here in Knoxville, KUB has seen a sharp increase in the number of trees needing removal due to the Emerald Ash Borer in recent years. As the trees die or show other symptoms of an EAB infestation, they are easier to spot, and KUB has increased efforts to remove necessary ash trees to lessen the negative impact on the system.
What should I do if I have a tree that has been impacted?
If the tree is near a KUB right-of-way, or near power lines, please call 524-2911 to report it. If the tree is on personal property, contact a certified arborist to assess your tree and get proper guidance on its treatment, or removal and disposal.
Can’t I just cut it down?
The main method of movement for this invasive pest is human transport, which is why it is of the upmost importance that proper removal and disposal methods are followed. You should not cut down the tree without first contacting a certified arborist to assess your tree and provide proper guidance on its treatment, or removal and disposal.
How can I prevent the spread of the EAB?
Since human transport is the primary mode of movement for the EAB, it is important that you collect and purchase firewood only where you intend to burn it. Locally, the Great Smoky Mountain National Park has implemented regulations on bringing firewood into the park. Also, purchase nursery stock from local sources, to again prevent the movement of the EAB.
Where can I get more information on the Emerald Ash Borer?
For Tennessee related information, please use the following resources:
For general information: