Emerald Ash Borer

What is the Emerald Ash Borer (EAB)?

Emerald Ash Borer (EAB) is a small invasive, wood-boring beetle that is native to Asia. EAB attacks and kills ash trees. EAB was first discovered in 2002 in Michigan, likely introduced via wood from shipping crates originating in China. 

See where EAB has been found in Wisconsin using the Wisconsin Emerald Ash Borer Detections Look-Up Tool.  

Is my tree an ash tree?

Ash trees have branches and buds that are directly across from each other (opposite branching). Ash tree leaves are compound and composed of 5-11 leaflets. Mature ash trees have bark that has diamond shaped ridges but young ash trees have relatively smooth bark. 

Use this Ash Tree Identification Guide (PDF) to help you determine if your tree is an ash tree.

How can I tell if my tree is infested with Emerald Ash Borer?

If your tree is an ash tree, it is likely that it already is or will be infested by the Emerald Ash Borer. It is difficult to see the early signs of an Emerald Ash Borer infestation. Signs of an Emerald Ash Borer infestation include:

  • Thinning canopy and dieback
  • Bark cracks and splitting
  • Loss of bark from woodpecker eating activity
  • Epicormic sprouting (suckers, water sprouts)

It is unlikely that you will see an adult EAB in your tree. Underneath the bark, you may see the larva or the evidence of the larva in S shaped galleries.

How does the Emerald Ash Borer kill ash trees?

EAB larva eat the inner bark of an ash tree, essentially eating away the tree’s circulatory system for transporting food and water. The inner bark does not grow back. Within 2 to 5 years of infestation the tree dies from lack of food and water. This causes the tree to become very brittle and the tree can easily be blown over or drop limbs. The amount of time it takes for an ash tree to die from an EAB infestation depends on the size of the tree and the size of the infestation.

Does the Emerald Ash Borer kill all trees?

The Emerald Ash Borer only attacks true ash trees in the genus Fraxinus - it does not target any other species of trees. EAB does not attack American mountain ash trees (Sorbus americana). 

If my tree is infested with Emerald Ash Borer, can it be saved?

Trees infested with EAB can be treated with a pesticide treatment to prolong their life. However, pesticide treatments are only effective if an ash tree has lost less than 30% of its canopy. Treatments must be repeated every couple of years. If an ash tree has lost more than 30% of its canopy, it is unlikely to survive even with treatment. Ash trees will die approximately two to five years after being infested by EAB, depending on the size and health of the tree.

Should I be planting or removing ash trees?

It is strongly recommended to not plant ash trees at this time due to the EAB and the significant number of ash trees already present in Menomonie. If you have an ash tree in your yard and it is healthy you don't have to remove it. The City recommends planting a new tree next to your existing ash tree to help mitigate the canopy loss when your ash tree needs to be removed. The City of Menomonie maintains a list of recommended tree species.

What is the City doing about Emerald Ash Borer?

The City has been monitoring public ash trees for signs of EAB infestation. The City has treated several ash trees in the past but is now focused on removing ash trees showing signs of infestation. The City plants new trees every year and has worked to secure grant funding to help assist in planting additional trees to offset the canopy loss from the removal of ash trees.


Ash Tree

Ash tree

Emerald Ash Borer shown on a penny for size

Emerald Ash Borer

Ash tree bark showing damage from emerald ash borer

Tree with Emerald Ash Borer damage

Bark Stripped Off Tree EAB

Ash tree infested with Emerald Ash Borer with bark stripped off by woodpeckers