Emerald Ash Borer has been confirmed again in the state of Nebraska.  Find out what that means for your beloved ash trees, what you should be doing now, and what you can hold off for a little while longer.

The Nebraska Department of Agriculture (NDA) confirmed the first finding in the state of Emerald Ash Borer (EAB) in a tree located in Omaha in 2016.  Nebraska will be the 27th state to confirm the presence of the pest since 2002.  More recently, it has been confirmed in Lincoln and Fremont.

There are several different types of borers that attack ash trees, so correct identification is key.  Finding borer holes in ash trees doesn’t necessarily mean you have EAB.  There are several different native borers that are normally found on ash trees.  The ash/lilac borer, banded ash clearwing and carpenter worm can attack healthy ash trees.  The redheaded ash borer, banded ash borer, flatheaded apple tree borer and eastern ash bark beetle attack stressed or dying ash trees.  Knowing exactly which insect is in your tree will let you know if you should start looking for a replacement or if you need to treat.

EAB is an invasive beetle that attacks and kills all species of ash.  It is a small, metallic-green beetle that is about 1/2 inch long. The larvae of this wood-boring insect tunnel under the bark of ash trees, disrupting the flow of water and nutrients, ultimately causing the tree to die.  EAB infested ash trees will exhibit thinning or dying branches in the top of the tree, S-shaped larval galleries under bark, D-shaped exit holes and suckers or advantageous growth along the trunk and main branches.

Know your trees.  Get them properly identified first before taking any further steps.  Proper identification is key to knowing if you should be concerned about EAB or not.  Ash trees have an opposite leaf pattern, or the buds are across from one another on the stem.  It also has a compound leaf that is made up of several smaller leaflets.  If you are lucky enough to get the seeded variety, the seeds look like paddle-shaped helicopters and are held in clusters on the tree.  Ash trees, those in the Fraxinus genus, can include the green, white, Patmore, Marshall’s Seedless, and Autumn Purple Ash.  Mountain Ash is not affected because it isn’t a true ash, it’s in the Sorbus genera.

If you do have an ash tree, know when you need to take action.  If your tree has EAB-like symptoms, like canopy thinning, branch dieback, sprouting growth from the base of the tree, or D-shaped exit holes, it should be examined by a professional.  Leave your ash trees in as long as they are healthy, in good condition, and in a good location.  If your tree is dying or diseased, it may be best to hire a certified arborist to look at your trees and determine the cause of the trees’ decline.

Treatments are not always recommended.  Once EAB has been confirmed within the 15 mile radius of your location, then you can begin the proper treatment applications on healthy trees.  Depending on the size of the tree, a soil drench is one option for homeowners.  The drench will need to be applied to the tree yearly throughout the lifespan of that tree.  Tree care professionals are able to use additional products like trunk injections.  Contact a certified arborist for these treatments. Time of year also plays a role in effectiveness of treatments.  Some products are best applied in the spring, while others can be done throughout the summer.  Right now, we are out of the treatment window and applications should be made in the spring.

Diversity, diversity, diversity.  Ash has been a popular landscape and conservation tree for a long time due to its fast growing nature and overall appearance. Diversity in the landscape is important to the overall health of the community forest.  Aim to have diversity, try not to have any one species make up more than 10% of the landscape.  This is helpful when we have infections and infestations occur so that a majority of the landscape isn’t affected by the one outbreak.  Now is an excellent time to start thinking about replacement trees for ash.

More information about the emerald ash borer, finding an arborist, and recommendations can be found at www.eabne.info.

Start preparing now for the ‘green menace’ to make its way into this portion of the state.

Elizabeth Killinger is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at elizabeth.killinger@unl.edu, her blog at https://huskerhort.com/, or HuskerHort on Facebook and Twitter.

Emerald Ash Borer Strikes Again (PDF)