Emerald Ash Borer Damage and Treatment

Ash Tree with Emerald Ash Borer Damage on the Bark
September 8, 2022

The Emerald Ash Borer (EAB) is an invasive insect originally from Asia. Their impressive color is worthy of the name, but these metallic-green beetles are so destructive that they can devastate an entire forest in just 10 years. Learn what you can do to treat your trees for Emerald Ash Borer beetles.

For more on the insects and how to identify them, check out our guide to Emerald Ash Borer beetles.

Emerald Ash Borer Damage

Emerald Ash Borers are the size of grains of rice, but their larvae cause colossal damage to ash trees by carving into the Cambrian layer of the bark and disrupting the transport of water and essential nutrients. An EAB infestation can be hard to detect until trees are too damaged to tolerate treatment, so it’s important to look out for the warning signs of Emerald Ash Borer damage such as:

  • Canopy Thinning: As the larvae damage the tree tissue, the upper canopy and branches start to die off. It should be noted that yellowing leaves can also be caused by a variety of tree diseases.
  • Increased Woodpecker Activity: The thinning bark and abundance of larvae and beetles can attract natural predators, such as woodpeckers.
  • Epicormic Shoots: Additional branches may begin to grow directly from the trunk of the ash tree, taking advantage of the openings left by EAB and competing for already limited resources in the trunk tissue.
  • S-Shaped Galleries Underneath The Bark: As larvae move around to feed, they create S-shaped or serpentine tunnels, about ⅛ inches wide. These tunnels are commonly filled with frass, which is a mixture of sawdust and droppings.
  • D-Shaped Exit Holes: When the adult EAB beetles emerge from the trees in June and July, they leave distinct D-shaped holes in the bark. These holes can have any orientation and are generally ⅛ inches in diameter.

As it can be difficult to identify the signs of an Emerald Ash Borer infestation, we highly encourage you to reach out to arborists or tree care professionals.

Emerald Ash Borer Treatment Options

Emerald Ash Borers are extremely invasive and can spread very quickly—in fact, a female EAB beetle can lay its eggs anywhere from 100 yards to 2-3 miles from its home tree. So if you notice any warning signs of a beetle infestation, consider one of the following application methods:

DIY Treatment Options

While some people may be tempted by DIY treatments of ash trees, they are generally ineffective, as they require the proper timing and dosage for the trees in question. No two trees are exactly alike, so no over-the-counter option can guarantee full elimination. Additionally, over-the-counter insecticide products don’t contain a high enough concentration of the ingredients required to save your trees, so you could be spending time and money on treatments that, according to research, aren’t powerful enough to combat an EAB infestation.

Bark Spray

Bark spray is most effective for trees that are still healthy enough to transport water, though sometimes added ingredients can help the insecticide disperse. A formula containing the active ingredient Dinotefuran is sprayed on the lower trunk and then gets systematically infused throughout the tree. This is one of the quickest and simplest treatments available.

Canopy Sprays

Canopy sprays are applied to foliage, and are more useful to control and kill adult borers, but not the tree-destroying larvae. Canopy sprays can be effective to curb the spread of EABs around the neighborhood, but have to be very carefully timed and require multiple applications.

Soil Injection

Soil injections are applied directly to the soil around the base of tree trunks. These require more specialized equipment than a spray but also work best under very specific soil and weather conditions. There may also be regulations regarding how much insecticide can be injected into the soil in a given area.

Trunk Injection

Trunk injection is one of the most effective EAB treatments that always requires professional help. The insecticide is injected directly into the tree bark and can kill EABs in multiple stages of life, including both larvae and young adults. Trunk injection can also offer lasting protection, usually around two years. It can be applied at almost any time of the year since it does not require optimum weather conditions to work.

Remove & Replace

Sometimes, a tree is just too far gone to respond well to EAB treatment, or the effort of removing and replacing a tree outweighs the cost of treatment. However, infested trees must be replaced with species approved by your city, and removal and replacement can become a significant time investment. A professional can help you determine what the best course of care is for your trees.

Call American Turf & Tree Care

At American Turf & Tree Care, we use powerful trunk injections that are proven to eliminate EABs and last up to two years, so that you don’t have to worry about recurring sprays. When you call us for EAB control, our expert technicians can inspect and determine the extent of EAB damage so that we can advise on the best way forward to protect the landscape you love. Call us immediately when you notice EAB-infested ash trees or fill out our contact form if you are interested in taking a proactive approach to protecting your healthy trees.

FAQ About Emerald Ash Borer

An Emerald Ash Borer infestation is intimidating, but with the proper knowledge, you can be confident in choosing the best treatment options for your trees.

How Can I Protect My Trees from Emerald Ash Borer?

Homeowners can protect healthy ash trees against EAB with systemic insecticides, such as imidacloprid. While preventative treatments are most commonly applied in the spring, pesticide applications in the fall can also prove useful when it comes to protecting your trees from EAB.

How Do I Know If My Tree Has Emerald Ash Borer?

These are some of the most common signs of an EAB infestation:

  • Yellowing leaves
  • Canopy thinning
  • Bark loss
  • Sprouts from the trunk of the tree
  • S-shaped galleries under the bark
  • D-shaped exit holes in the bark

If the infestation is active, you may also see green, shiny beetles crawling around your ash tree.

Can A Tree with Emerald Ash Borer Be Saved?

In most cases, yes! EAB treatments using systemic insecticides are 85-95% effective when applied correctly. Getting professional treatment from a tree care company ensures the best chances of success

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