hand holding a stethoscope against a tree

Emerald Ash Borer Treatment and Prevention

With thousands of ash trees destroyed across North America since 2002, the need for an effective emerald ash borer treatment is more pressing than ever. There are roughly seven billion ash trees across North America and these trees are one of the dominant species in our forests and urban and suburban canopies. The speed with which emerald ash borers breed, feed and spread places our entire population of ash trees under threat. The article that follows will provide you with all you need to know about this invasive insect. It will also discuss the best available treatment methods.


What Is the Emerald Ash Borer?

 Agrilus planipennus, commonly known as the emerald ash borer, is a kind of beetle that is native to northeastern Asia and, as its name suggests, feeds exclusively on ash trees. It was found in North America only in 2002 and there was very little research into its life cycle and habits up to that time. Outside of its native range, it is a highly destructive pest and has resulted in the near decimation of large numbers of ash trees throughout North America and Europe. Much of the research being done today is funded by local, state, and provincial governments on the continent, with a view to containing the insect’s spread and preventing further destruction of the native ash population. Although we identify the species by its adult form, it is actually the larvae that cause the damage.

Emerald Ash Borer

What Does an Emerald Ash Borer Look Like?

 The emerald ash borer has a distinctive, even beautiful, jewel-like appearance. Adult beetles are about .33 ins in length and .063 in width. They have an unmistakable metallic green color with some copper hues. When the wings and elytra (the hard outer wing) are spread, the bright red of the beetle’s abdomen becomes visible. Despite their very distinctive appearance, there is still a tendency for adults of other species to be misidentified as emerald ash borers.


Where Did the Emerald Ash Borer Come From?

 The emerald ash borer is endemic to northeastern Asia and can be found in countries such as Russia, Mongolia, northern China, Japan, and Korea. It is uncertain exactly how they were brought to North America, but it is theorized that it first arrived here on the solid wood packing material carried in cargo ships or planes.

As things currently stand, since the beetle was first found in North America, it has been found in ash trees in 25 U.S. states, as well as in at least three Canadian provinces.


4 Signs of Emerald Ash Borer Damage

 There are many insects that can leave marks of feeding or infestation on plants. It is necessary to identify the distinctive signs that signal the presence of emerald ash borers. The insects themselves are not that easy to spot and the larvae are virtually impossible to see unless you peel off some bark and look very closely. Here are four signs to watch out for to confirm whether or not you are dealing with emerald ash borer:


  1. Thinning Canopy and Yellowing Leaves:

As the ash borer larvae feed under the bark, they damage the xylem and phloem tissues that carry water and nutrients to all parts of the tree. As dehydration and starvation first start to set in, the initial signs will be seen in the canopy, which will start to thin out. The leaves will also start to look pale, unhealthy, and yellow. This can be caused by other factors, however, such as disease or poor quality soil. So if you see this, you need to look for other signs to confirm an infestation.


  1. Suckering:

Trees in survival mode will try to sprout branches and leaves wherever they still can. As the canopy thins, you may start to see new growth near the base of the tree or on main branches. This phenomenon is called epicormic sprouting or suckering. This a general sign of stress and, like thinning canopy, could have other causes. Again, you will have to look for other signs to confirm an infestation.


  1. D-Shaped Holes:

This is a sure sign of emerald ash borer infestation. When the young adult ash borers emerge from the inside of the tree in June and July, they leave unmistakable D-shaped exit holes. The holes are about 1/8” wide and could be oriented in any direction. While there are other borers that leave exit holes, they always have very different shapes. Most native borers will leave oval or round exit holes.


  1. Splitting Bark and S-Shaped Galleries:

When you peel away some bark and look beneath, you will know you are looking at an emerald ash borer-infested tree if you see a chaotic series of S-shaped tunnels or galleries. These are the tunnels that the larvae make as they feed. They are approximately 1/8” wide and are filled with a mixture of sawdust and insect excrement, which is referred to as frass. The trees attempt to form callus tissue around these galleries, which causes the bark to split vertically.


The Emerald Ash Borer’s Life Cycle

 As mentioned above, adult ash borers emerge from under the bark in June and July. The females lay eggs in crevices in the bark. It takes about 7 to 10 days for the eggs to hatch. The larvae then bore under the bark and feed on the xylem, phloem, and bark. This is what cuts off the flow of water and nutrients.

During the course of the following winter, the larvae nestle in their feeding galleries and, during April and May, the mature larvae pupate and gradually transform into adults, emerging a month or two later and starting the cycle again. Adult beetles feed on the leaves of the ash tree and do not cause any further damage but, by that stage, the damage to the tree has already been done.


Emerald Ash Borer Prevention

 As a result of all the research that has gone into this species and its life cycles and habits, preventative treatments have been developed that have proven very effective in keeping ash trees safe from infestation. These should be applied by professionals as there are many factors to be considered. The health of the tree needs to be assessed to see whether it can effectively be preserved. In some cases, the infestation may be too far gone. Ash trees that have not yet been infested, or those where the infestation has not developed too far, can be treated with a variety of preventative measures. These include soil injection, trunk injection, bark spray and canopy spray. The injection methods are the most common, as they deliver the product directly into the tissue of the tree, allowing them to then be spread throughout the canopy by the tree’s natural transpiration movements. If you are concerned about ash borer infestation, call a professional immediately to assess your trees.


How to Get Rid of Emerald Ash Borer

 The most common way to control emerald ash borer is by means of the soil or trunk injection methods mentioned above. Diluted insecticides, which are selected for being non-toxic to the trees, are injected into the soil of the trunk and are then spread throughout the plant in its water supply. As the larvae feed on the bark and phloem tissues, they consume the insecticide and die. The majority of chemicals that are used for this are not approved for use by homeowners, and need to be administered by professional pest control services.


How Much Does Emerald Ash Borer Treatment Cost?

 It is not advisable to attempt treating your trees against emerald ash borers on your own. You should rather engage the services of an arborist or pest control professional. It is difficult to estimate how much this would cost, as it depends on the size of the tree, location, the choice of insecticide, application method, and call-out fees. It is best to consult service providers in your area and compare your options and quotes. As the borer population has yet to be brought completely under control, you will need to apply these treatments on an annual basis.

For more information, or to get a quotation for an emerald ash borer treatment, contact us.


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