Emerald Ash Borer Identification & Treatment


Thanks to the fact that it grows in every region across the country, the ash tree is one that many will recognize. Although there are dozens of different species, most offer:

  • Lush foliage
  • Dense canopy
  • Intermittent flowers

Unfortunately, the many species of ash that exist across North America currently face a growing epidemic: the emerald ash borer. This invasive, wood-boring beetle, which gets its name from the distinctive hue of its body, is slowly spreading across the country.

The infestation, first reported in Michigan in 2002, was determined to be the result of beetles from Eastern Asia that traveled to the United States in solid-wood packing materials. From there, they have spread to several states and even into Canada, reportedly killing tens of millions of trees over the last decade. If the infestation continues unchecked, several billion more will be threatened.

Because the species seems to have no natural predators in North America, it has flourished. But people are now taking steps to stop the growth of this tiny pest and save the many species of ash that exist in rural and urban areas alike.

If you are a lover of ash trees, have them on your property, noticed signs of distress in your ash population, or simply want more information on this topic, keep reading to learn how to identify and eradicate this invasive species in your neck of the woods.

How to Identify an Ash Tree

There are thought to be as many as sixty-five different species of ash tree growing across America, from the white, black, blue, and green ash of the Eastern United States to the Mexican, Texas, Arizona, and Oregon ash species of the West and Southwest.

Although they differ slightly in appearance and characteristics, ash varietals can generally be identified by a number of similar traits. As members of the Oleaceae family, ash trees share common features with both olive trees and lilac bushes, including:

  • Ash is a dense hardwood that can reach the size of a large shrub or a large tree, depending on the species.
  • The leaf structure is pinnately compound, or arranged so that leaves grow evenly on either side of a shaft, or small branch, similar to a feather.
  • Ash trees also produce flowers, as well as samara. The latter is commonly known as a “helicopter seed” because of the way it spins like the blades of a helicopter as it falls from a tree.

In order to properly identify the ash in your area, you’ll need to learn more about the traits specific to species native to your region. A guide to North American trees is a good bet, although you could also find nearly unlimited information online.

Signs, Symptoms, & Damage

Spotting an infestation of emerald ash borers may not be easy until the damage has already been done.

  • Although adults of the species only feed on leaves, the eggs they leave behind are the real threat because larvae will grow and feed on the wood of the tree.
  • The harm to infected trees will quickly become evident as the beetles disrupt the progression of water and nutrients from the root system to the trunk and upper portion of the tree.
  • Signs of tree distress could present with bark splits, girdling, dying leaves and branches at the crown of the tree, and strange growth. Branches sprouting from the base of the tree would be such a sign.

As for evidence of the beetles themselves, larvae leave distinctive D-shaped holes in the wood or bark of the tree when they reach maturity and emerge. When bark is removed, you may be able to see the winding, serpentine tunnels they’ve bored into the wood.

Emerald Ash Borer Treatment

Although some birds, such as the woodpecker, are prone to eating the larvae of emerald ash borers, there is not enough of a natural threat to slow the progression of the beetle in North America. Because of this, insecticides appear to be the best option for extermination.

There are several types of insecticides suited to the task, but some are only available commercially, meaning that individual homeowners may not be able to purchase them. Here is a brief overview of the products that may be used for extermination.

Consumer products:

  • Soil drench method: Both Bayer Advanced Tree and Shrub Insect Control and Optrol may be purchased by homeowners and applied to the soil surrounding infected trees during early spring to fight emerald ash borer infestation.
  • Granules method: Ortho Tree and Shrub Insect Control Ready to Use Granules offer a prime solution for most homeowners, thanks to easy application in late spring.

Professional grade products:

  • Soil drench/injection method: There are several products designed to eliminate beetle infestation that fall into this category, including Merit and Xytect, which must be applied in early spring or mid-fall, as well as Safari and Transect, which can be applied in late spring.
  • Trunk injection method: The trunks of infected trees may be treated directly with products like AzaSol and Imicide, both of which may be applied in late spring, as soon as new foliage has started to grow.
  • Systematic bark spray method: Tree bark may be saturated with products like Safari and Zylam Liquid at the same time as the trunk injection method is used.
  • Cover spray method: By using products like Astro, Onyx, and Tempo, the trunk, branches, and foliage of infested trees can be sprayed in two applications – four weeks apart – when temperatures are around 50 degrees Fahrenheit.


Emerald Ash Borer Treatment Cost

The cost of emerald ash borer treatment will depend on several factors, including

  • Number of trees infected
  • Scope of the infestation
  • Whether or not you elect to eliminate emerald ash borer beetles on your own or with the help of a professional exterminator

Consumer treatment options could start as low as $25-$50 for a single unit of insecticide (one bottle, up to a gallon, depending on the product). Hiring a professional service will be significantly more expensive.


Emerald ash borer eggs are only about a millimeter in diameter and are white in color, although they turn reddish brown when fertilized. Mature members of the species feature long, narrow bodies that are approximately a third of an inch long.

Mature beetles are only about the size of a grain of rice, making them extremely difficult to spot, despite their vibrant color. Unfortunately, this means that signs of infestation generally don’t occur until the first larvae have emerged from the tree, leaving their telltale holes behind.

Life Cycle

The eggs of the emerald ash borer are deposited in the bark of the ash tree, after which the larvae cycle through four stages before reaching full maturity, a process that can take one to two years. During that time, they wind their way through the bark of the tree in a serpentine fashion, feeding as they go.

Once they emerge, mature beetles will live only about six weeks, but females can still lay up to 200 eggs during that time.

With a decided lack of natural predators in North America to thin the numbers of both larvae and adults, the species has seen exponential growth over the past ten-plus years. In order to stop the advance of the emerald ash borer and save the North American ash from ultimate extinction, the use of insecticides may be the only way to interrupt the breeding and feeding cycle of this invasive beetle.

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