Are Ash Trees In Denver Still At Risk of EAB Infestation?

It’s been a few years since the Emerald Ash Borer (EAB) was first spotted in the Denver metro area. Since then, the infestation has continued to spread throughout the city. In this article, we’ll provide an update on the latest news and information regarding EAB for Denver homeowners. We’ll describe the local forestry and government actions being taken to help prevent the spread of EAB, as well as some of the measures you can take to protect your own ash trees.

EAB Denver Infestation Summer 2022

The Emerald Ash Borer (EAB) is an invasive beetle that was first detected in Colorado in September of 2013. Since then, the EAB has spread to Boulder in 2013, Broomfield in 2019, and most recently, Arvada in 2020. It takes two to four years for signs of EAB infestation to become apparent, so Denver Parks and Recreation and local forestry experts remain vigilant.


According to Colorado State University Extension, 15% of the trees that make up Colorado’s urban forest are ash and the Denver Metro area alone has an estimated 1.45 million ash trees. The EAB is a serious threat to ash trees and has killed tens of millions of ash trees across the United States. In Colorado, the EAB has killed over 50,000 ash trees since it was first detected in the state!

Local Forestry & Government Actions

To help prevent the spread of EAB and to protect our ash trees, Denver has put in place various emerald ash borer management strategies including tree quarantines, tree inventories, assessing the ash tree population, and introducing biocontrol measures, EAB identification workshops, and more.

Be A SmartAsh

The Denver Parks and Recreation Department launched a special division dubbed Be A Smart Ash in 2016, as an effort to support emerald ash borer management strategies and help Denver homeowners care for their ash trees.


Comprised of friendly city foresters, the Smart Ash team provides technical assistance, educational resources, and tree care recommendations to the community. Their work is part of Game Plan for a Healthy City, Denver’s larger initiative to create and maintain well-maintained and equitable green spaces for all of Denver’s residents.


Here’s a list of activities the Be A Smart Ash team is currently involved in and how they can help you beat the EAB:

  • Educating and enlisting the help of Denver residents in identifying, treating, and replacing ash trees now and over the next 15 years.
  • Taking care of ash trees located on city property.
  • Helping residents take responsibility for any ash trees on their personal property and in adjacent public rights-of-way.
  • Empowering residents with as much information as possible to help them protect their trees from pests.
  • Planting new trees to help grow our city’s urban canopy.
  • Helping residents replace ash trees that are at risk of EAB.
  • Taking care of our existing Denver trees and equipping tree owners with the information they need to care for their trees through proper watering, mulching, pruning, and more.


Foresters are eager to partner with Denver homeowners to strengthen the city’s urban canopy. After all, healthy trees are better able to fight off infestation! Take advantage of some of these incredible programs available to you:

Apply For a Tree

The Denver Parks & Recreation wants to help you plant a tree. If you have room in the public right-of-way adjacent to your property, you may even be eligible to have a free tree planted for you! Simply submit a free application and your underground utilities will be marked, a certified arborist will mark your property, deliver and plant your free tree! Adding more non-Ash trees to the urban canopy helps strengthen it through diversity.

Ash Tree GAP Removal & Replacement Program

In an effort to mitigate the spread and impacts of the Emerald Ash Borer, Denver is offering an incentive for the removal and replacement of infested and high-risk ash trees on private property. Under this program, eligible property owners will receive up to $100 per tree toward the cost of removal and replacement of an emerald ash borer-infested or high-risk ash tree.

To be eligible, trees must be:

  • Located on private property within the emerald ash borer quarantine area in Denver
  • A minimum of 12 inches in diameter (measured at breast height)
  • An emerald ash borer-infested tree, or a high-risk ash tree as identified by the City Forester

Reuse My Tree

Have an Ash tree that needs to be removed? Make the best of a sad situation and repurpose your tree! Rather than sending it to a dump, Denver is looking to turn more of our trees into functional products if they must be removed. Your old tree could become a beautiful table, door, or even a bicycle!

Tree Quarantines

In an effort to prevent the spread of emerald ash borer, Denver has established a city-wide quarantine for all ash trees and firewood of all species. This means it is illegal to transport any ash tree products – including logs, branches, wood chips, mulch, and stumps – out of the city.

What Can Homeowners Do?

Denver city officials and foresters are doing their best to control the spread of EAB, but it truly needs to be a community effort. As a homeowner, you can help by not transporting firewood and by properly disposing of any ash tree products.

Know the Warning Signs

If you have an ash tree on your property, it is important to keep an eye out for signs of EAB infestation, such as:

  • D-shaped holes in the bark
  • Suckering at the base of the trunk
  • Crown dieback
  • Epicormic sprouting


You should also be familiar with the pest itself. The EAB can be identified by:

  • Its emerald green body
  • Length of about ¼ inch
  • Six legs and two antennae


How Can I Protect My Ash Tree from the EAB?

If you have an Ash tree on your property, there are a few things you can do to protect it:

  • Water and fertilize regularly: this will help your tree be more resistant to pests and diseases. Ash trees need deep watering, so make sure to give them a good soak once a week during the summer.
  • Prune properly: Ash trees should be pruned in the late winter while they’re dormant. Avoid topping or removing large branches, as this will make your tree more susceptible to wind damage and disease. Regular pruning will remove places for the EAB to lay its eggs.
  • Mulch: Mulching helps retain moisture and provides nutrients to the tree. Apply a layer of mulch that’s two to four inches deep, making sure to keep it away from the trunk. This will help retain moisture and keep the roots of your tree healthy.

What if my Ash Tree is Infested by the Emerald Ash Borer Beetle?

The best way to determine if your Ash tree is under attack from the EAB is to have one of our certified arborists check your trees. With years of experience, they can spot signs of risk or damage quickly and provide expert consultation on the next steps.


If an Ash tree becomes infested with EAB there are typically a few possible solutions:


  1. Monitor: If the tree is healthy, it may be able to withstand an infestation and continue to live for several years. It may not be necessary to take drastic measures.
  2. Treat the Tree: There are a few insecticides that can be used to prevent EAB from damaging ash trees. Treatments must be applied regularly (usually every two or three years) to be effective.
  3. Remove and Replace the Tree: If a tree is already infested or has suffered significant damage, the best course of action may be to remove it and replace it with a different species of tree. Denver’s emerald ash borer task force is working hard to prevent the spread of EAB in our city.


Treating with insecticides can be effective when the infestation is caught in very early stages. That’s why vigilance and surveillance are key! The best way to apply these insecticides is as a preventative measure before EAB has had a chance to invade the tree. It is not recommended for homeowners to apply these treatments themselves. Only trained arborists should administer these insecticides on a carefully regimented tree care plan.


If you think your tree might be infested with Emerald Ash Borer, give us a call today. One of our trained arborists will come out to take a look and determine if your tree is infested and needs treatment. Staying proactive and ahead of the curve helps keep the Denver community EAB-free!

Contact our expert arborists to schedule your free consultation today!