EAB in Denver Trees – How Prevention Measures Can Protect Against the EAB Beetle

Fielding Tree EAB beetle Denver

It’s that time of year, prime pest-prevention season. We’ve got the latest important updates on the EAB activity in the front range area and tips for how to act now to save your trees.

The Emerald Ash Borer beetle has caused devastation to ash trees in many states, and Colorado is no exception. The dry conditions this year have made the trees more susceptible to EAB infestation, so it is important to take preventative measures now.

There are several things you can do to protect your ash trees from the Emerald Ash Borer beetle. In this blog post, we will discuss how to prevent EAB infestation in Colorado in 2022 and how to treat an existing infestation.

EAB 101

As the temperatures in Denver continue to rise and the drought-like conditions persist, the Emerald Ash Borer beetle is spreading at an alarming rate. The beetle bores into the bark of ash trees and lays eggs, which will hatch and kill the tree within a few years.

How Do the EAB Damage Colorado Trees?

Emerald Ash Borers damage trees by tunneling under the bark and eating the phloem, which is the layer of tissue that transports nutrients from the leaves to the rest of the tree. This feeding disrupts the tree’s ability to move water and nutrients up and down, causing the tree to starve and eventually die.

How Do the EAB Spread?

EAB infestation is not a concern just for the Department of Forestry or local government officials, it is a problem that affects the whole Denver community. The EAB spreads by flying from tree to tree and by hitching a ride on infested firewood, nursery stock, or other objects that come into contact with the trees.

They can travel quite a distance in a short time period. We know EAB adults can fly at least 1/2 mile from the ash tree where they emerge, and they have been found as far away as 12 miles from the nearest infested ash tree.

Their lifecycle also contributes to the rapid spread of the infestation. The female EAB lays about 60 to 100 eggs during her lifespan. She lays her eggs in the cracks and crevices of ash bark, and in 7-10 days the larvae hatch and then tunnel into the tree to feed on the inner bark. This feeding disrupts the tree’s ability to transport water and nutrients, eventually killing the tree.

What Actions Are Local Leaders Taking to Save Denver Trees?

The Emerald Ash Borer is active in Boulder, Denver, and Jefferson counties. It was first found in Boulder, CO, in September 2013. According to the Colorado Department of Agriculture, the Denver Metro area has an estimated 1.45 million ash trees. EAB infestation Colorado statistics show that over 17,000 trees have already been treated or replaced and front range municipalities have spent over 9 million dollars collectively on management strategies.

With so much at risk, Denver officials stepped up.  EAB prevention Denver action has been swift. In an effort to stop the insect from continuing to spread and kill more ash trees, local leaders have implemented a few different strategies including:

Quarantines: To help prevent the movement of firewood and other ash products that could harbor the EAB, Denver has placed areas of the city into quarantine. This means that no ash materials are allowed to leave these designated areas.

This measure may seem a little extreme, but it is actually one of the most effective ways to stop the EAB from spreading. By keeping all potential carriers (firewood, logs, branches, etc.) in check within city limits.

Inventory & Detection: Significant resources have been allocated to help identify and track any EAB activity. City workers are surveying neighborhoods for ash trees, looking for signs of infestation or damage.

If you have an ash tree on your property, it is important to be vigilant and look for the following symptoms: 

  • EAB Adult Beetles and Larvae present
  • Broken branches towards the trunk of the tree
  • A dying canopy of leaves
  • D-shaped exit holes in ash tree bark
  • Bark splintering and S-Shaped Tunnels
  • Increased woodpecker interest or damage
  • Epicormic Shoots

Management: Management tactics generally include some combination of monitoring, preemptive removals, infestation tracking/analysis, reactive removals, trap trees, and chemical treatments. When it comes to prioritizing trees to treat or remove, criteria such as “poses a public safety hazard,” “is historic tree” or “important entryway to the community” are taken under consideration.

The Current EAB Crisis

The City of Denver is currently in the midst of a severe drought, which has created conditions that are stressing trees and making them more susceptible to infestation by the Emerald Ash Borer beetle.

The dry weather means that EAB larvae are not being killed off by drowning, as they would be in wetter climates. It also means that there is less water available for the trees, making them more susceptible to drought stress.

The City is currently treating approximately 900 infested ash trees and removing another 500. The goal is to treat or remove a total of 2000 ash trees by 2022.

Drought and Tree Stress

The current drought has several negative impacts on Denver trees.  In addition to the Emerald Ash Borer, other pests and diseases are taking advantage of the stressed trees.

The drought also dries out soils, making them more susceptible to erosion. This can lead to loss of soil and degradation of water quality. All this adds up to a perfect storm for trees in Denver.

With defenses down and their immune systems weak, Denver trees will have extreme difficulty fending off an EAB infestation. Healthy trees have the ability to fight back, so the best thing you can do right now is to take steps to help your trees regain their strength.

EAB Prevention Measures

There are several steps you can take to help your trees regain their vitality and prevent an infestation of Emerald Ash Borer. Proper watering, mulching, trimming and fertilizing can all make a big difference before the EAB emerge in late spring and early summer.

Watering Trees

Trees need at least one inch of water per week to stay healthy. During times of drought, they may need up to two inches per week, especially if there is absolutely no rain. You can help trees get the water they need by using a soaker hose or drip irrigation system, and by watering deeply and infrequently rather than shallowly and daily.

Mulching Trees

Mulch is a layer of material (usually organic) that you spread around the base of a tree. It helps to conserve moisture after rainfall and watering.  It also protects the tree’s roots from extreme temperature changes, compaction, and weed growth.

You should spread a layer of mulch that’s about two to four inches deep, making sure not to pile it up against the trunk of the tree. We recommend using wood chips, shredded bark, or pine needles.

Winter Tree Trimming

EAB prevention Denver tips include professional tree trimming and pruning. It’s important to trim trees in the wintertime or very early spring because it’s when the tree is dormant. This way, you won’t harm the tree and you’ll be able to see which branches need to be trimmed.

There are a few other reasons why trimming and pruning can help fend off EAB infestation:

  • The cold weather will help to seal the cuts that you make, making them less susceptible to infection and EAB infestation.
  • Winter is a good time to trim trees because there’s usually less wind and rain, which can cause the wounds to heal more slowly.
  • Trimming and pruning remove dead and weak wood that EAB prey on.


Fertilizing your trees is like giving them vitamins.  It helps them to be strong and healthy, which in turn helps them to fight off pests and diseases.

When you fertilize your trees, you should use a slow-release fertilizer so that the nutrients are released over time. This is especially important in the spring when trees are starting to grow again after a long winter.

There is no one-sized-fits-all fertilizer, but our expert arborists can create a custom fertilization plan based on what your Ash trees need. We can also provide recommendations for the appropriate method of fertilizer application and how often it is needed.

Schedule Services Now

The EAB waits for no one! It is important to be proactive and schedule preventative care services now. In the plant and tree care industry, timing is everything. The sooner you act, the more likely your Ash trees are to survive. March and April are perfect months to get quotes for treatment in the spring.

Many treatments require more than one visit from our team, so it’s best to get on the books and mark your calendar in advance. 

If you have any questions or concerns about EAB and how it affects Colorado, please do not hesitate to reach out. Our team is here to help in whatever way we can.

We have years of experience fighting on the front lines to save Denver Ash trees from this pervasive pest. Our passion for providing outstanding care for your trees is rooted in the belief that all Denver trees are worth saving!

Schedule online or call our friendly staff today to get a free consultation!