Emerald Ash Borer

Emerald Ash Borer admin February 21, 2023


How to Protect Your Ash Tree from the Emerald Ash Borer

Emerald Ash Borer (EAB) is the most destructive insect for trees ever recorded in North America. According to the Colorado Department of Agriculture, this green metallic beetle was found in Boulder, Colorado, and has spread since its discovery.

Which Colorado Cities has EAB been Discovered?

In 2013 the borers were found near 30th and Iris in North Boulder, and later that year, more were found on the University of Colorado campus. During the month of June 2016, the emerald ash borer was found inside the city limits of Longmont. In 2017 the borers were found in Lafayette, in 2018 beetles were found in Louisville and Superior CO, and in 2019, they were found in Broomfield, Westminster, and outside of Berthoud. In 2020, it was found in northern Fort Collins. As of 2021, it was found in Erie, CO.

EAB is responsible for killing more than 50 million ash trees in over 20 different states. To put this in perspective, the Mountain Pine Beetle is responsible for devastating much of our Colorado’s forests and if left untreated the Emerald Ash Borer will do the equivalent to our urban forests. The Colorado Department of Ag estimates that one in five trees in Colorado is an ash tree. The good news is there are preventative measures to protect ash trees.

To mitigate the potential for damage/loss to ash trees, Organo-Lawn strongly advises all of the following actions and services for all ash trees.

Emerald Ash Borer

Emerald Ash Borer (EAB) Treatment Recommendations

Berthoud, Boulder, Broomfield, Erie, Fort Collins, Lafayette, Longmont, Louisville, Loveland, Lyons, Niwot, Superior, or Westminster CO

Emerald Ash Borer Control Using Tree-Age

If your ash tree has never been treated for EAB we recommend a trunk injections using a special insecticide called Tree-age. This injection can be applied any time there are leaves on the ash tree. This insecticide will kill EAB larvae if the tree has already been infected and it will also protect the ash tree for up to three years.
Tree-Age is a special insecticide for the treatment of Emerald Ash Borers. Tree-Age only needs to be applied once and it will kill any larvae that are living inside the tree and it will prevent the tree from being attacked for up to 3 years.

After the initial treatment of Tree-Age we recommend waiting 2 years and then starting preventative treatments of an insecticide called Criterion. If preventative Criterion applications are performed annually then no further applications of Tree-Age will be necessary.

Important Note: If tree care trunk injections are too expensive or if you have a lot of ash trees and you live inside the quarantine area we recommend at minimum treating your ash tree using our soil injection. Keep in mind if the EAB is already in the tree then the soil injection will not control the pest.

Other cities near the quarantine but no confirmed cases.

Preventative Emerald Ash Borer Treatment

  • To protect your ash trees’, we strongly recommend deep root soil injections of a special insecticide called Crterion.
  • This Emerald Ash Borer treatment needs to be applied once per year before an Emerald Ash Borer attack occurs.
  • Ideally this would be applied every autumn between the months of September to early November.
  • This is extremely important to do proactively because it will not work re-actively.
  • It is extremely difficult to identify if a tree has already been attacked by the Emerald Ash Borer. An ash tree that has been attacked may not show any signs of damage for up to 5 years.
  • This preventative soil drench application needs to be applied once a year moving forward until further notice.

Emerald Ash Borer Treatment Outside the County of Boulder

If you own an ash tree and live in Arvada, Golden, or other cities outside of the county you need to decide if your tree is of high value and worth treating proactively. At this time the preventative soil injection is at the discretion of the property owner, but these recommendations may change if Emerald Ash Borer is found in more cities across the Colorado Front Range.

Emerald Ash Borer Treatment - Longmont CO
Tree-Age is a special insect control for Emerald Ash Borer. It will kill the larvae that is living inside the tree and protect the tree from an attack for up to 3 years.
Deep Root Tree Fertilization - Boulder
This Organo-Lawn tree care technician is applying a special soil drench insecticide to protect this tree from an insect attack.
Emerald Ash Borer Treatment - Boulder CO
The adult beetles lay eggs in the bark cracks of the Ash tree.

An Insight to the Emerald Ash Borer

How To Identify Symptoms of the Emerald Ash Borer

Emerald Ash Borer Boulder Treatment
Woodpecker activity and damage increases where they are trying to get to the EAB larvae in the tree.
Emerald Ash Borer - Insect Control for Trees - Boulder Colorado
Canopy die-back will begin at the top of the ash tree progressing downward until the tree is bare.
Emerald Ash Borer Boulder
Canopy die-back will begin at the top of the ash tree progressing downward until the tree is bare.
Bark splitting may occur exposing “S”-shaped galleries caused by the larvae of the EAB.
Later stages of infestations, ash trees may form sprouts from the trunk and/or roots.

Questions and Answers about the Emerald Ash Borer

Where did the emerald ash borer come from?

Emerald ash borer (Agrilus planipennis), was introduced accidentally into Michigan. It possibly arrived from wood packing material imported from eastern Asia sometime in the 1990’s. It became well established in Michigan until ash trees started dying in 2002, when it was first detected. It is responsible for the deaths of tens of millions of ash trees in the Midwest and eastern U.S.

How long has the emerald ash borer been in Colorado?

The emerald ash borer was first detected near 30th and Iris in North Boulder, CO. on September 23rd, 2013. It was confirmed on September 26th, 2013.

At this time, it has also been found in South Boulder and on the University of Colorado campus. It has been found in every part of town in Boulder and was discovered in Longmont on June 6th, 2016, Lafayette in 2017, and Lyons and Superior in 2018. According to the Department of Agriculture, it may have been in Colorado since 2010.

Does Emerald Ash Borer attack trees other than Ash?

No, it will only attack ash trees.

EAB Recommendations from the Colorado Department of Agriculture

  • Do not plant new ash trees.
  • Never move firewood of ash trees out of the area.

Preventative measures should be taken because initial detection of EAB can be difficult. It may take up to five years for the canopy of an infested ash to show signs of thinning and decline. Since borers infest the upper branches of the tree, the “D”-shaped holes cannot be seen from the ground until the tree is severely infested.

Emerald Ash Borer Boulder

EAB emerging from an ash tree in Fort Collins.

Emerald Ash Beetles
Emerald Ash Beetles emerging from an ash tree.
Emerald Ash Borer Treatment Boulder Colorado
Emerald Ash Borer
Emerald Ash Borer Fort Collins Colorado
EAB emerging from an ash tree in Fort Collins.

What is the Life Cycle of the Emerald Ash Borer?

Adults emerald ash borer’s emerge between mid-May through late July, and they will feed on ash leaves (this is where the preventative Criterion or Safari insecticides will provide protection). They mate, and then the females lay eggs (average of 60-90 per female) in bark cracks. Larvae hatch from the eggs within one week and then bore through the bark and into the trunk of the tree. The larvae then feed under ash tree bark from mid-summer through the next spring, producing the “S”-shaped tunnels (This is where Tree-Age will provide control). They pupate in the spring and the next generation of adults may emerge.

Emerald Ash Borer Life Cycle

Emerald Ash Borer Information

Emerald Ash Borer

The information that is available on to the general public is often confusing and sometimes incorrect. We have tried to answer some of the most frequently asked questions about EAB and why this is an insect you do not want to ignore. If you have an ash tree on your property it is important to understand what you need to do to protect your ash tree from being attacked.

How far can EAB travel?

The EAB adults can fly ½ – 1 mile a year. On a windy day borers can fly much farther and borers can also be spread via the transportation of firewood from infested trees.

Very Important: NEVER move ash firewood from ash trees out of the area.

Does Emerald Ash Borers only attack dying or stressed trees?

No, whereas most boring insects tend to prey upon stressed or weakened trees, emerald ash borer may attack both healthy and stressed trees. Typically, a healthy tree will have a better chance of surviving an attack than a weak tree.

How big of problem is EAB?

Huge! It is a major problem that should not be ignored. The Emerald Ash Borer is now considered the most destructive forest pest ever seen in North America. It has killed tens of millions of ash trees in southern Michigan alone. Emerald Ash Borers are not an insect that you want to ignore. An attack from enough emerald ash borers will easily kill a healthy ash tree.

How to tell if a tree has been attacked by the Emerald Ash Borer?

Initial detection is extremely difficult. It may take 4-5 years after an attack for the canopy of an infested ash to show signs of decline. When a tree shows thinning or decline, it is usually too late to save the tree. EAB start by attacking the upper branches of ash trees. As the adult beetles leave the tree they make D shaped holes in the truck of the tree. By the time the D shaped holes are visible at the base of the truck the tree has already been severely attacked. Unless you are climbing into the top of the tree it is difficult to tell if a tree is attacked. This is why preventative insect treatments are so important when dealing with the Emerald Ash Borer.

Do Treeazin applications control EAB?

At this time we are recommending applications of Tree-age instead of Treeazin. We are suggesting this because Tree-age has a significantly higher control rate and provides control for a longer period of time. We will be doing more research into Treeazin for possible future use, but at this time we consider Tree-age applications to be a better choice for control of the Emerald Ash Borer.

Are aerial insecticide sprays effective against EAB?

No, EAB feed in the tree differently and will not be controlled via most insecticide sprays. Criterion Soil injections will work only if in the tree has not been attacked and trunk injections will work both if it has been attacked and before an attack.

Are there any ash trees you do not recommend treating?

The only ash trees that are not worth treating are ash trees that are weak, severely stressed, and are already struggling because of improper planting, lilac ash borer, heat stress or other problems. These are basically low quality ash trees that are unlikely to be able to absorb the trunk or soil injections. These trees are typically not worth treating because they are probably not going to live longer than a few years anyways.

Ash Borer Lookalikes
Click on Image to Enlarge
Emerald Ash Borer Treatment Boulder Colorado

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Professional Lawn Care Companies

We understand that insect controls for trees can be confusing due to the many nuances of how each product works. If you have any questions about the Emerald Ash Borer or if you want to talk with a tree care expert please contact our office to answer your tree care questions. Use This Link to Learn More About the Other Insects that Affect Front Range and Colorado Trees Organo-Lawn of Boulder (303) 499-2000 or Fort Collins (970) 225-9425

FAQ – Emerald Ash Borer

What type of trees do Emerald Ash Borers attack?

In North America, ash trees are the only tree species that are susceptible to an emerald ash borer attack. Trees in forests, as well as urban landscaped areas are known to be affected. Larval galleries of the EAB larvae have been found in trees or branches measuring as little as 1-inch in diameter. All species of North American ash to be susceptible to EAB pressure.

How do Emerald Ash Borers kill a tree?

The ash tree is killed from nutrient deprivation and drought. Adult Emerald Ash Borer insects will first feed on the leaves of the tree. The feeding on the leaf tissue will do little or no harm to the tree but after nibbling, the beetle will then bore into the trunk of the tree and lay eggs. When the eggs hatch the larvae will feed on the cambium layer, which is underneath the bark of the tree. The larvae create S-shaped tunnels, which hinders the trees ability to push nutrients and water into the canopy of the tree. If there are enough Emerald Ash Borer larvae in the tree there will be too many paths bored in the tree and the tree will be unable to push any water or nutrients to the upper parts of the tree.