UPDATE On the Emerald Ash Borer (EAB) : Arvada Confirms Infestation

Fielding Tree EAB beetle Denver

Denver trees are under siege as the EAB spreads to Arvada. Take advantage of the small window of time left to treat and protect your trees before the Emerald Ash Borer peaks.


Emerald Ash Borer (EAB) Breaking News

In breaking news, Thursday, June 18th, the city of Arvada officially confirmed the presence of the Emerald Ash Borer beetle, or EAB as it’s often called. The Emerald Ash Borer beetle is a highly invasive species that attacks and kills Ash trees. According to city officials, Arvada has about 97,000 ash trees that could be devastated by an infestation of EAB, and the majority are on private residential land.


Since arriving in Boulder, Colorado in 2013, the Emerald Ash Borer has spread to the cities of Westminster, Longmont, and Broomfield. Now Arvada is under attack. To slow the spread of EAB, the Colorado Department of Agriculture and County of Boulder enacted a quarantine of raw Ash material when the EAB first arrived. Although the quarantine stopped the human spread of EAB, such as transporting infested firewood, it could not fully contain the pests which are able to fly upwards of half a mile and travel to new territory on their own. The quarantine was lifted in December of 2019, and ashwood is now allowed to be moved freely throughout the state of Colorado.


The major benefit of the EAB quarantine was that it gave surrounding areas time to prepare for the impending infestation. The cities of Broomfield and Westminster took proactive steps such as reducing the ash tree population on public lands, treating high-value ash trees with chemical controls, and developing biocontrols to combat the EAB. The city of Arvada developed a thorough Emerald Ash Borer Management Plan that was released this May, just weeks prior to the confirmed presence of the pest. 


Arvada EAB Management Plan

What is the city of Arvada doing to control EAB and save Ash trees? Check out these highlights from their four-part management plan:


Public Ash Tree Inventory

The city is completing a full inventory of the number and location of ash trees to be managed. So far, 1,400 Ash trees in parks, streetscapes, and other irrigated areas have been identified. The inventory does not include trees growing in natural areas or Arvada’s two golf courses. To date, only five percent of trees in the current public inventory are considered in ‘good condition’. This small group of public Ash trees is considered ‘high value’ and will receive insecticide applications.



Arvada forestry staff have been developing effective ways of detecting EAB since they first arrived in Boulder in 2013. Current methods include:

  • visual survey
  • trap trees
  • plastic traps
  • chemical lures
  • branch peeling
  • contractor reporting


Early detection is critical for saving Ash trees, but it can be tough, even for experienced arborists. Experience with EAB in nearby cities shows that there is often a 3-4 year gap between when trees become infested and when they are actually diagnosed and removed. Arvada staff hope to close this gap with early detection strategies.


Ash tree Removal and Replanting

EAB prey on Ash trees that are stressed or injured. Arvada officials are strategically removing public Ash trees that display visible structural defects, trunk wounds, and native insect infestations such as Lilac/ash borer, and other pests. 


The goal of removing these ash trees and replacing them with non-ash species is to improve the overall resilience of the urban forest to EAB attack. City officials report that 90 ash trees have been removed in the last few years. Although this might seem extreme, research shows that injured Ash trees do not respond well to chemical treatment and their removal will reduce the food supply for EAB. Forestry experts are mindful of Denver’s unique urban canopy and seek to replace the removed Ash trees with a variety of native trees.


Chemical Treatments

The harsh reality is that all untreated Ash trees will be killed eventually by the Emerald Ash Borer. The city is taking swift action and investing in chemical treatments, where appropriate, to save as many Ash trees as possible. High-value public Ash trees are being treated with trunk spray, which provides one year of protection, or trunk injections, which offer 2-3 years of protection.


Residents Responsible For Saving Their Own Ash Trees

Although Arvada has acted consciously to save Ash trees on public land, the responsibility of protecting ash trees on private property falls completely on the homeowner. Chemical treatment is the best approach for protecting your Ash trees from the destructive EAB, but timing is everything. There is a very small window of time to maximize the potential of chemical treatments and effectively protect your Ash trees. 


Here is what you can do now:


Keep Watch For EAB Warning Signs

One of the best things you can do to protect your trees is to learn the EAB warning signs. If you spot them on trees in your neighborhood or community, you can potentially save your trees before it is too late. Stay vigilant! Here are the warning signs:


  • 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

Keep in mind that an infected tree may have only a few or any combination of these warning signs. Ash trees with minimal EAB larvae may even show no external symptoms of infestation!


Schedule Insecticide Preventative Treatment Now

Chemical insecticides are available to effectively treat landscape ash trees threatened by EAB. It is best to begin using insecticides while ash trees are still relatively healthy. If insecticide treatment begins after the first signs of infestation, such as canopy thinning, it can stop additional damage, but it will not reverse any damage that has already been done. 


EAB Insecticides work systemically and have to be transported within the tree. This means that a tree must be healthy enough to transport a systemic insecticide up the trunk and into the branches and canopy. Trees within an established EAB infestation have developed galleries under the bark that prevent the transport of the insecticide throughout the tree, and therefore it will not be effective in these trees.


Insecticides that can effectively control EAB fall into four categories

  • systemic insecticides that are applied as soil injections or drenches
  • systemic insecticides applied as trunk injections
  • systemic insecticides applied as lower trunk sprays
  • protective cover sprays that are applied to the trunk, main branches, and foliage. 


Here are two types of treatment and delivery that we recommend for the best success:


  • Soil root injection to prevent EAB infestation: this is a two-year protection program that protects against EAB and Aphids only. Studies have shown uptake is higher and the treatment more effective when the soil root injection product is applied at the base of the trunk where the density of fine roots is highest.


  • Direct tree trunk injection to protect against EAB infestation: This is three-year protection that protects against EAB and Aphids. One advantage of trunk injections is that they can be used on sites where soil treatments may not be practical, effective, or appropriate, including trees growing on excessively wet, sandy, compacted, or restricted soil environments. They also yield rapid results!


Act Now To Protect Your Trees

Spring is the ideal time of year to apply insecticide treatment for EAB protection, but there is still time to get the application. The timing has to do with the life cycle of EAB. There is a small window of opportunity to control the adults before any new eggs or larvae are produced. The onset of adult beetle emergence begins in late June and peaks two to three weeks later, lasting through July. 


Strong And Healthy Trees Fight Infection

In the same way that healthy bodies can fight off infection, healthy trees that are well-watered and fed can defend themselves better from all types of insect infestation. We recommend feeding your ash trees to keep them healthy and give them a better chance of survival. At Fielding Tree & Shrub Care, we’ve developed a reliable plan of action that includes proper watering and fertilization for protecting trees from EAB. 


Know Your Enemy: EAB Basics

  • The Emerald Ash Borer Beetle is a non-native wood-boring insect and has no natural predators in the U.S.
  • The EAB is now arguably the most destructive pest in the United States, killing all types of North American ash species, including autumn purple ash, a popular white ash varietal in Colorado.
  • In the larval stage, EAB cuts off the flow of water and nutrients to the tree by feeding under its bark. Once a tree falls victim to infestation, there is no saving it.
  •  Humans moving ash firewood or ash nursery stock are thought to be responsible for the known cases of EAB moving long distances. For this reason, the movement of other untreated ash wood, wood chips greater than one inch, and ash products (green lumber, pallets, etc.) should be avoided at all costs.


Take Action Today


Without a doubt, the Emerald Ash Borer is the most destructive forest pest in U.S. history. Untreated Ash trees will be devastated and dead within four years. Waste no time! The EAB will emerge any day, but you can still save your trees.


We are prepared to expertly help you during this stressful time. Protecting your trees is completely within your control. Contact one of our certified arborists at Fielding Tree & Shrub Care today for a complimentary consultation. They can explain how EAB might personally affect your property, and go over all your customizable treatment and preventative care options.


Act now to save your trees and schedule your complimentary on-site inspection with Fielding Tree & Shrub Care today!