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Emerald ash borer detected in city

In September 2019, Emerald Ash Borer (EAB) was confirmed in Westminster, in the vicinity of 128th Avenue and Zuni Street. This follows EAB being confirmed a few weeks earlier in adjacent Broomfield. Learn more about the EAB.

Now is the time to act to save your valuable ash tree! 

What can I do to save my ash?
  1. Determine if you have an ash tree
  2. Decide if your ash tree can be saved
  3. Look at treatment options
  4. Act! 
Do I have an ash tree?

Green ash, white ash and Autumn Purple ash are very desirable for landscape planting because they grow well under difficult conditions and have been widely planted. There are an estimated 69,000 ash trees in the city. Use this identification key to determine if you have an ash. The EAB/ash tree ID app can be downloaded by searching in app stores for “ash trees.”

This smart phone app is available to help determine if a tree is an ash tree: Ash Tree App

Can my ash tree be saved?

Survey your property for the number, size and location of ash trees. Determine if the tree is worth saving. Is the tree healthy, in a good location, and with minimal prior injuries? View the Managing EAB Decision Guide  Healthy ash trees in a good location with a trunk diameter greater than eight inches can and should be saved! 

Treatment Options

There are preventative pesticide applications that can be given to protect ash trees.  The most effective, environmentally-safe pesticide is emamectin benzoate, which is injected into the trunk of the tree by a certified pesticide applicator. It is effective for two and possibly three years and the approximate cost of an application is $150-250 for an average sized tree in Westminster. Imidacloprid is a pesticide available to homeowners under several trade names and can be applied as a soil drench. It is less expensive but the effectiveness is inconsistent and care must be taken when applying to avoid killing pollinators and other animals. Please review these pesticide options for treating EAB.

Remove ash trees that are not candidates for preservation treatments. Once EAB is fully established, all ash trees that have not received preservation treatments will be killed. It will be more expensive and more dangerous to remove ash trees after they have been dead more than two years. It is highly recommended to hire a qualified arborist to safely remove trees.

How to find an arborist

Search for tree companies or arborists that offer EAB treatments. They must be certified by the Colorado Department of Agriculture to do pesticide applications. It is highly recommended to hire a Certified Arborist through the International Society of Arboriculture at: Find an Arborist . Search by location with your postal code within 50 miles. Be sure to check the company's references, and make sure they have liability insurance. It is recommended that you get several bids before selecting a company. 

EAB will kill all ash trees that are not treated once the insect population builds up! 

Remove & Replace 

Plant replacement trees in existing empty planting spaces. This will lessen the impact from the future loss of ash trees. Consider planting new trees under existing ash trees so they can become established before the ash tree is removed. Plant replacement trees after the removal of ash trees, Use a broad diversity of tree species when planting to avoid monocultures that can be destroyed by pests like EAB and Dutch Elm Disease. Download our list of recommended replacement tree species.

What is Emerald Ash Borer?

Emerald Ash Borer (EAB) is a non-native invasive insect pest first reported in Michigan in 2002 and it has since spread to 35 states and is responsible for killing millions of ash trees. EAB attacks all species of ash and generally kills the trees within three to five years.

EAB was confirmed in Boulder in 2013, Gunbarrel in 2015, Longmont in 2016, Lafayette and Lyons in 2017, Superior in 2018, Broomfield, Westminster, and Berthoud in 2019, and Arvada and Fort Collins in 2020.

It is difficult to detect new infestations of EAB. The insect has usually been in the tree for two to three years before symptoms are visible.

Signs of an EAB infestation include:

  • branches without leaves, especially at the tops of ash trees
  • vertical splits in the bark exposing S-shaped tunnels
  • wild leafy branches (new growth) sprouting from the trunk
  • D-shaped exit holes

The symptoms of EAB are similar to other insect and abiotic problems. Ash trees have struggled in the last several years from drought conditions, the late freezes and the commonly found lilac ash borer. Lilac ash borer is a native insect that has attacked ash trees for many years and frequently kills branches in the tree and sometimes the entire tree.

The quarantine restricting the movement of ash firewood, logs and nursery stock from Boulder County served its purpose of slowing the spread of EAB and has ended as of Dec. 31, 2019. 

Further information can be found at the following links: 

Colorado Department of Agriculture website

Colorado State Forest Service Quick Guide 

Colorado State Forest Service Green Menace

What is the city doing?

Westminster has approximately 1,300 public ash trees. Of those, 990 trees were identified for preservation treatments based on their size and condition. The city has treated 700 trees to date and will continue treating the remaining trees next year. 

Why should we care?

There are an estimated 69,000 ash trees in Westminster, comprising about 13 percent of the tree canopy. One out of every seven trees is an ash with a collective appraised value of $69 million. The loss of these trees will decrease property values in Westminster by $2.8 million as the attractiveness of our businesses and homes decline.

If all 69,000 ash trees were removed, the cost would be $21 million with replacement costs of $28 million. The loss of the ash tree canopy will increase storm runoff, increase erosion and decrease water quality. The loss of shade will increase air temperatures, increase energy consumption and increase irrigation water usage.