Adult Emerald Ash BorerA destructive insect pest that has killed many thousands of ash (Fraxinus) trees in the mid-section of the United States was discovered in Boulder in 2013. Since the initial infestation was found, Emerald Ash Borer (EAB) has spread further throughout Boulder County. The extent and spread of the beetle continues to be monitored closely by Boulder County, Colorado State Department of Agriculture, Colorado State Forest Service, CSU extension and surrounding front range communities. Although there are quarantines and restrictions in place for movement of ash wood out of Boulder County, it’s generally accepted that EAB will eventually make its way outside of Boulder County into all communities surrounding Boulder, Denver, and Golden.

It has become apparent that the Emerald Ash Borer now presents an increasing threat to Golden’s population of approximately 15,000 ash trees.

Although the insect has not been found in Golden as of yet, the history of this insect’s movement into 22 other states has shown that, without treatment, entire populations of ash trees are almost inevitably killed, and it is important for residents to understand the treatment options available. Chemical treatments have been proven effective and, because they are relatively inexpensive to apply, property owners with ash trees that they do not want to lose should be aware that now is not too early to consider applying a preventative treatment.

Anyone interested in protecting their ash tree, most commonly Green Ash (Fraxinus pennsylvanica) or White Ash (Fraxinus americana) should consult with a certified arborist. There are several treatment methods available. The most effective chemical treatment involves a trunk injection which must be re-applied every 2-3 years and requires a certified applicator. Other treatment options are also available. For further information regarding the best chemical treatments, visit

If your ash tree is in poor health, and you do not intend to commit to a treatment regimen, it is recommended that you consider removal and replacement. You can also plant now, with the intent to remove your ash tree in the future when EAB makes its way into our community.

Ash trees were widely planted on the front range in Colorado in the past because it thrived here, but is no longer recommended as a planting choice anywhere in Colorado. City of Golden Forestry staff have selected around 300 ash trees for treatment. They are in good planting locations, considered to be highly valuable to the community, in good condition, and good candidates for future treatments. Ash trees in park areas and streetscapes that are in poor health will be marked for removal and replacement while focusing on tree population diversity to avoid any similar species specific pests in the future.

The City of Golden intends to continue to conduct branch sampling and an on-going search for evidence of  EAB in our community into the foreseeable future. If you are uncertain whether a tree you value on your property is an ash or not, or if you have any other questions or concerns, please contact the City’s Forestry office at 303-384-8141 or