Emerald Ash Border (EAB)

Emerald Ash Borer- Exotic ash pest

Emerald Ash Borer (EAB) is an invasive pest that affects white and green ash, as well as the lesser known host, the white fringe tree. EAB is of huge concern in Colorado, because a large percentage of our urban trees are Ash. Ash trees are great trees and are common because they grow quickly, provide beautiful fall color, all while being hardy enough for our tough climate.

EAB adults feed on the leaves, and lay their eggs in crevices of the bark. Once these eggs hatch, they burrow into the trunk/limb, feeding within the vascular cambium of the tree. This effectively girdles the tree, cutting off nutrient supply and water, eventually leading to death. Ash trees affected by this pest are often more dangerous to prune, remove, or leave standing, due to the weak and brittle wood after infestation. It’s best to treat trees before they become damaged from EAB. However, a general rule of thumb is that if the tree is damaged 30% or less from the insect, then treatment may still be effective.

If you think your tree has Emerald Ash Borer, we would be happy to send one of our ISA certified client arborists out to take a look with you, and discuss the best options going forward. Below we’ve provided some things to keep an eye out for, as well as common treatment options. 

How Do I Know if my tree has Emerald Ash Borer?

  1. Canopy Thinning — we typically see evidence of EAB from the ground in terms of canopy thinning. When a tree is infested with EAB, they often put out “thinner” or smaller leaves from one section of the canopy. Another phenomenon similar to this is “flagging.” Flagging is evident when one branch dies back, or leaves turn yellow during the growing season.

  2. D Shaped Exit Holes on Limbs/Trunk — the most telltale sign of Emerald Ash Borer is the D shaped exit holes. These holes occur after the insects overwinter, and emerge from the trees as adults. Although at times difficult to spot from the ground, if you have a bad enough infestation, you may be able to see this damage on the main trunk.

Benefits of Saving Your Ash Tree

  • Aesthetics — trees help provide beauty within our urban environments. Studies show trees can actually help improve our mental health. What better way to get through the day than gazing upon a beautiful tree from your living room or office?

  • Environmental — trees are one of the best ways to sequester carbon from our warming environment. Big Ash tree on the south side of your house? That provides a number of cooling benefits, helping you reduce energy costs, thus reducing your impacts on the environment.

  • Property Values — looking to sell your home sometime in the future? Trees can add great property value. Mature, large trees are hard to come by in our Front Range landscape. Maintaining the ones you have will be a more cost effective option instead of replacing!

Treatment Options

  • Chemical Treatments — We have multiple treatment options to help protect our community’s ash tree population from EAB. These treatments vary and the recommended treatment for your ash may be different than your neighbor's as we are able to tailor each treatment to you and your tree’s needs.

  • Tree Removal — Some ash trees will be so infested (and dangerous to leave standing) that we cannot save them. At this point, we would recommend removal and replanting. With our service options, we could remove the tree for you, grind the stump, and plant a new tree.