Emerald Ash Borer Control

Learn how to protect your ash tree from Emerald Ash Borer, the most destructive insect in North America

Emerald Ash Borer (EAB) is considered the most destructive forest pest ever seen in North America. According to the Colorado Department of Agriculture, this green metallic beetle was found near 30th and Iris in North Boulder and on the University of Colorado campus during the fall of 2013. Durning the month of June 2016 the emerald ash borer was foiund inside the city limits of Longmont. EAB is responsible for killing more than 50 million ash trees in over 20 states. To put this in perspective, the Mountain Pine Beetle is responsible for devastating much of our Colorado mountain 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 tree.

Emerald Ash Borer Boulder

Emerald Ash Borer


Emerald Ash Borer (EAB) Preventative Preventative Treatment Recommendations:


For Property Owners Inside the City of Boulder, Niwot, and Longmont

Trunk Injection – For residents that live inside the city of Boulder, Niwot, and Longmont.

  • If your tree has never been treated for EAB we recommend a trunk injections using a special insecticide called Tree-age. This injections 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 applications need to be applied once and it will last in the tree for 2-3 years.
  • After the second year has passed the tree will require annual applications of Merit Soil Injections to protect the tree moving forward. If preventative Merit injections are performed every year no further applications of Tree-age will be necessary.
  • Important Note: If 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.

Arborjet Boulder

For Property Owners Inside the County of Boulder but Outside the Cities of Boulder, Niwot and Longmont
  • Insecticide Soil Injection – For residents that live outside of the City of Boulder, Niwot and Longmont but inside of or near Boulder County. (Erie, Louisville, Lafayette, Superior, and Lyons)
  • To protect your ash trees' we strongly recommend deep root soil injections of a special insecticide called Merit and it needs to be applied proactively once per year. Ideally this would be applied every autumn between the months of September to early November if weather permits. If the fall months were missed then anytime from April to early June the tree should be treated using an insecticide called Safari. This insecticide is a fast acting preventative and will prevent the Emerald Ash Borer, but it will only work if the tree has not already been attacked. This is extremely important to do proactively because it will not work reactively. It is difficult to identify if a tree has been attacked because it may not show any signs of damage for up to 5 years, even after it has been severely attacked.
  • This preventative soil drench application needs to be applied once a year moving forward until further notice.

Tree Fertilizing Boulder

Property Owners Outside the County of Boulder
  • If you own an ash tree and live in Arvada, Golden Westminister, Broomfield, Ft. Collins, Loveland, Laporte, Windsor, Frederick, or Firestone 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.


Property Owners Looking to do More to Help Protect Their Ash Trees
  • Better Treatment Plan for EAB- Soil Injection or Trunk Injection + Deep Root Tree Fertilization
    • Deep Root Tree Fertilization both spring (April-May) and fall (Sept – Early November) is important because the healthier we can keep the tree the better it will be able to survive or fight off an attack.
  • Best Treatment Plan for EAB-(Soil Injection or Trunk Injection + Deep Root Tree Fertilization + Winter Tree Trimming)
    • Winter Tree Trimming to prune dead branches and strengthen the tree. Dead branches weaken the tree; an unhealthy tree is much less likely to survive an Emerald Ash Borer attack.


Other Important 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 and it may take up to five years for the canopy of an infested ash to thin 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.


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 possibly 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. 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.


Signs of Emerald Ash Borer Infestation May Include:


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Woodpecker activity and damage increases where they are trying to get to the larvae in the tree.

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Canopy die-back will begin at the top of the tree progressing downward until the tree is bare.

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Later stages of infestations, ash trees may form sprouts from the trunk and/or roots.

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Bark splitting may occur exposing “S”-shaped galleries caused by the larvae of the EAB.

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Although difficult to see, the adult beetles leave a “D”-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they leave the tree as an adult.


What do emerald ash borers look like?

Emerald ash borers are a bright, metallic-green color. They are approximately ½” long and have a flattened back. They can be mistaken

for other green insects, so a positive identification by a professional is necessary.

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Emerald Ash Beetles emerging from an ash tree.

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EAB emerging from an ash tree in Fort Collins.

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Emerald Ash Borer


What is the Life Cycle of this Borer?

Emerald Ash Borer Life Cycle

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Adults emerald ash borer's emerge between mid-May through late July, and they will feed on ash leaves (this is where the preventative Merit 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.

How far can EAB travel?
The EAB adult flies ½ - 1 mile a year. However, 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 it 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; but 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.

How do I know if an ash tree is infested with Emerald Ash Borer?
Initial detection is not easy. It may take 4-5 years for the canopy of an infested ash to thin and decline. When a tree shows thinning a decline it is usually too late to save. Since borers infest the upper branches of the tree, and they only make the D shaped holes upon exiting the tree the D shaped holes may be seen until the tree is severely infested. Long story short is it might be impossible to tell if a tree is infested, until it is too late. This is why preventative measures are so important when dealing with the EAB.

Is Organo-Lawn doing applications of Treeazin?
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.


What is Organo-Lawn recommending for treatment options to help protect ash trees?


Which Colorado Cities to treat using Tree-age trunk injections include:

  • Boulder,
  • Niwot
  • Longmont.

Which Colorado Cities to treat using soil injections include:

  • Erie
  • Lafayette
  • Louisville
  • Superior
  • Lyons.

Note: If you live in Arvada, Golden Westminister, Broomfield, Ft. Collins, Loveland, Laporte, Windsor, Frederick, or Firestone you do not need to treat for EAB, but these recommendations might change quickly in the near future. We are suggesting preventative treatments for high value trees.

Why is proper deep root tree fertilization important for ash trees?

The healthier a tree is the better it can fight off and/or survive attacks.

Why is Winter Tree Trimming important for ash trees?

Removing dead branches and creating a strong structure is always beneficial for a tree and will only make the tree healthier.

Are aerial sprays effective against EAB?

No, EAB feed in the tree differently and will not be controlled via sprays. Merit 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 that will make the tree unlikely to be able to absorb the trunk or soil injections. These trees are not worth treating because they are probably not going to live but a few years anyways.


If you have any questions about Emerald Ash Borers in Colorado please contact Organo-Lawn, your local tree care expert. Boulder (303) 499-2000 Fort Colins (970) 225-9425