The Nebraska Department of Agriculture (NDA) confirmed Emerald Ash Borer (EAB) was found in a trap at the Blue Valley Campground in Seward, NE in early August 2020. This article will share information from Elizabeth Killinger, Extension Horticulture Educator, about what this means for your ash trees and what you should be doing now.

“Finding borer holes in ash trees doesn’t necessarily mean you have EAB. There are several different types of borers that attack ash trees, so correct identification is key. 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.

Proper tree identification is key to knowing if you should be concerned about EAB or not. The bark of ash trees have diamond shapes or capital “A’s”. Ash trees have an opposite leaf pattern, or the buds are across from one another on the stem. They also have leaves of 5 to 7 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.

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 decline.

Because of the cost, treatments are only recommended for high value and/or already healthy trees. 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 can be applied to trees with under a 20” diameter trunk yearly throughout the lifespan of that tree. Tree care professionals are able to use additional products like trunk injections on larger trees. Contact a certified arborist for these treatments. Some products are best applied in the spring, while others can be done throughout the summer. We don’t recommend treatments this fall.

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 and try not to have any one species make up more than 10% of the landscape. A diverse landscape isn’t as affected by single outbreak. Now is an excellent time to start thinking about replacement trees for ash. For a list of replacement trees visit The Nebraska Forest Service list of replacement trees or Trees for Western Nebraska (PDF). More information about the emerald ash borer, finding an arborist, and recommendations can be found at https://nfs.unl.edu/nebraska-eab.”