Ash TreeA destructive insect pest which has killed many thousands of ash (fraxinus) trees in the mid-section of the United States was discovered in Boulder in September. Since then, the insect has been found in several other sites in that city and it is not certain how widespread the infestation may be. Boulder and the Colorado Department of Agriculture continue to search for evidence of the borer and 16 ash trees have been removed at the CU-Boulder campus.

It has become apparent that the EAB now presents an increasing threat to Golden’s population of approximately 15,000 ash trees, especially since the landfill several miles north of our city along Hwy 93 (which has been included in the state-mandated quarantine area) will likely be receiving infested ash tree material in the relatively near future.

Adult Emerald Ash Borer
Adult Emerald Ash Borer

Although the insect has not been found in Golden as of January this year, 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, either green ash or white ash (common names: Marshall Seedless, Summit, Autumn Purple, Patmore), should consult with a certified arborist, a licensed pesticide applicator and/or the Colorado Dept. of Agriculture website. The most effective chemical treatment involves trunk injection, which requires a trained applicator. The simplest treatment, available at hardware stores and garden shops, utilizes a controversial chemical imidacloprid, which some environmentally sensitive people may wish to avoid. For further information regarding the best chemical treatments, visit Treatments are most effectively applied mid-April to mid-May.

The City of Golden intends to conduct an on-going search for evidence of the 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 would permit branches from your ash tree to be removed for sampling, we will be compiling a list of properties to visit in 2014 and beyond. Please contact the city’s Forestry office at 303-384-8141 or