Signs Your Ash Tree May Be at Risk from the Emerald Ash Borer Beetle

Common Larvae galleries to look for. The larvae feed off the inner bark and phloem. This interrupts the flow of water and nutrients to the tree.

Ash trees are a common and valuable part of many landscapes, providing shade, beauty, and habitat for wildlife. Unfortunately, these trees face a serious threat from the Emerald Ash Borer (EAB), a small but destructive beetle that has killed millions of ash trees across North America. Knowing how to spot the early signs of an EAB infestation can save your ash tree or at least help you take action before the damage becomes irreversible.

This post will guide you through the key signs that your ash tree may be in danger from the Emerald Ash Borer beetle, what to look for, and what steps you can take to protect your trees.

What Is the Emerald Ash Borer?

The Emerald Ash Borer is a metallic green beetle native to Asia. It was first discovered in the United States in 2002 and has since spread rapidly. The beetle’s larvae burrow under the bark of ash trees, feeding on the inner bark and disrupting the tree’s ability to transport water and nutrients. This damage eventually kills the tree, often within a few years of infestation.

Because the beetle is small and the damage happens beneath the bark, early detection is challenging but crucial.

Early Signs of Emerald Ash Borer Infestation

1. D-shaped Exit Holes on the Bark

One of the most distinctive signs of EAB infestation is the presence of small, D-shaped exit holes on the trunk and branches. These holes are about 1/8 inch wide and are created when adult beetles emerge from the tree.

Look closely at the bark, especially on the lower trunk and larger branches. The holes may be scattered or clustered.

2. Vertical Splits in the Bark

As the larvae feed under the bark, they create tunnels that cause the bark to split vertically. These splits often appear on the trunk and larger branches and may ooze sap.

If you notice fresh sap flowing from these cracks, it could be a sign that the tree is stressed by the beetle’s activity.

3. Crown Thinning and Dieback

The tree’s crown (the upper branches and leaves) will start to thin as the infestation progresses. Leaves may become sparse, smaller than usual, or wilted. Branch dieback often begins at the top of the tree and moves downward.

This symptom can be mistaken for drought stress or disease, so it’s important to look for other signs of EAB.

4. Epicormic Sprouting

When an ash tree is stressed or damaged, it may produce new shoots or sprouts from the trunk or lower branches. These shoots, called epicormic sprouts, are a response to the tree’s struggle to survive.

If you see clusters of sprouts on the trunk, it could indicate that the tree is under attack.

5. Woodpecker Damage

Woodpeckers feed on EAB larvae beneath the bark, so increased woodpecker activity on an ash tree can be a clue. Look for areas where bark has been chipped away or for small holes made by the birds.

While woodpecker damage alone does not confirm EAB, it is a useful sign when combined with others.

How to Confirm an Emerald Ash Borer Infestation

If you suspect your ash tree is infested, you can take a few steps to confirm:

• Peel back bark: Carefully remove a small section of bark to look for S-shaped larval galleries beneath. These winding tunnels are a telltale sign of EAB larvae feeding.

• Use traps: Some local forestry or extension offices provide EAB traps that can help detect adult beetles.

• Consult an expert: A certified arborist or local extension service can inspect your tree and provide a diagnosis.

  
  

What to Do If Your Ash Tree Is Infested

Treatment Options

• Insecticides: Several systemic insecticides can protect ash trees from EAB if applied early. These treatments are often injected into the tree or applied to the soil. They require professional application and may need to be repeated every 1-2 years.

• Tree removal: Severely infested trees that are dying or pose a safety risk should be removed to prevent the spread of EAB to nearby healthy trees.

• Biological control: Some natural predators and parasites of EAB are being introduced in affected areas, but this is a long-term strategy.

  
  

Preventive Measures

• Regular monitoring: Check your ash trees annually for signs of EAB.

• Avoid moving firewood: Transporting ash firewood can spread EAB to new areas.

• Plant diversity: Consider planting a variety of tree species to reduce the impact of pests like EAB.

  
  

D-shaped exit holes on ash tree bark caused by Emerald Ash Borer

Why Early Detection Matters

Emerald Ash Borer spreads quickly and kills trees within 3 to 5 years of infestation. Early detection allows you to treat your tree before the damage becomes fatal. Trees treated in the early stages often recover and remain healthy for many years.

Ignoring the signs can lead to the loss of valuable shade trees, increased costs for removal, and a negative impact on your local environment.

Final Thoughts on Protecting Your Ash Trees

Recognizing the signs of Emerald Ash Borer infestation is the first step to saving your ash trees. Look for D-shaped exit holes, bark splits, thinning crowns, epicormic sprouts, and woodpecker damage. Confirm suspicions by inspecting under the bark or consulting a professional.

If you catch the infestation early, treatments can protect your tree. If not, removal may be necessary to protect other trees nearby from infestation.

Keep an eye on your ash trees, act quickly if you see signs of trouble, and help slow the spread of this destructive beetle in your community. Your trees will thank you.