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Emerald Ash Borer Information

The recent confirmation of Emerald Ash Borer (EAB) within the City of Boulder introduces a new tree pest to the metro-Denver urban forest that could impact 100’s of thousands of property owners across the Front Range of Colorado. Denver alone has an estimated 330,000 ash trees at risk, and losing these trees will have adverse economic, environmental and social impacts on our community. Over the next decade EAB has the potential to destroy more of Denver’s urban forest than any other disease or pestilence in history.

State officials have established quarantine boundaries for Boulder County, and it is important to stress that this is currently the only known infestation in the state.  The Colorado Department of Agriculture will be working to perform inspection and sampling surveys across the City of Boulder in an effort to determine the extent of the infestation. 

Since the announcement of EAB being found in Boulder, Denver’s Forestry staff members have completed several hundred miles of inspections and at this point no signs of EAB have been found within Denver. 

With now over a decade of EAB experience in North America, it has become very clear that ash trees can be well protected through proper preventative pesticide treatments. The Colorado Department of Agriculture does not recommend property owners start EAB preventative treatments until an infestation is found within 5 miles of a property.

At this point in time Forestry is working to identify significant ash trees within parks and public rights-of-way, and developing an official EAB response plan for Denver.  If you have specific questions about park ash trees, or the right-of-way ash trees adjacent to your private property send a message to

Below are some helpful links for property owners seeking further information:

Colorado Department of Agriculture EAB Webpage  
How to Identify Ash Trees  
How to Identify EAB  
EAB Pesticide Treatment Research  
EAB Life Cycle  
Frequently Asked Questions