City of Thornton News Release Logo For Immediate Release:   6/16/2022
Contact: Thornton Parks, Golf and Forestry
Superintendent Paul Burkholder, 303-255-7840

Emerald Ash Borer Detected in Thornton
This non-native, wood-boring beetle attacks and kills ash trees

THORNTON, CO…Experts from Colorado State University Extension (CSU Extension) have confirmed the presence of Emerald Ash Borer (EAB), an invasive, highly destructive tree pest, in the city of Thornton. Thornton’s tree inventory shows approximately 1,600 ash trees on public property, however, the number of ash trees on private property in Thornton make the number significantly higher. “If all the ash trees are lost to the EAB, it will have a significant impact on Thornton’s tree canopy and general landscape,” says Thornton Parks, Golf and Forestry Superintendent Paul Burkholder.

The Emerald Ash Borer was first confirmed in Colorado in Boulder in 2013, and the Thornton confirmation is the first in a Colorado city east of I-25. Thornton Parks and Forestry made the initial find in an ash tree in Park Village Park, located near the center of the city. “It’s probable that the EAB has already infested other ash trees in Thornton,” says Burkholder. “The larger ash trees in Park Village were treated in 2021, so this recent find tells us EAB has been there for several years prior to treatment.” Nothing can be done to stop the spread of the EAB. The only useful action is pesticide treatments prior to infestation.

According to CSU Extension, since the 1960s, ash trees were often planted in home landscapes, parks and public areas across Colorado because they were in good supply in nurseries and grow quickly compared with other tree species.

For more information about ash tree identification, the symptoms of EAB and pre-treatment options, visit For more information regarding Thornton Parks and Open Space visit