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Emerald Ash Borer

Forestry Division, Public Works & Natural Resources

emerald ash borerEmerald Ash Borer (EAB) is a non-native, wood-boring beetle that can attach all ash (Fraxinus) tree species. This insect was first discovered in Michigan in 2002, and since then it has spread to 22 states, with Colorado being the most recent. The ash tree is very commonly planted tree in many communities. EAB has killed tens of millions of ash trees in the United States. Once the EAB population builds in numbers, ash mortality is near 100%.

The City of Boulder first discovered and confirmed the presence of EAB in September 2013. Boulder Urban Forestry delimitation survey determined EAB has spread within the City of Boulder. EAB has now been found in 5 of the 40 one mile grids surveyed.

On November 12, 2013 the Colorado Department of Agriculture established a quarantine zone around Boulder County, the City of Erie, and the Republic Landfill (north Jefferson County) off of Highway 93.

Quarantine Map

Longmont is estimated to have an ash tree population of approximately 43,000 trees. City of Longmont Forestry Services has conducted an initial ash inspection survey and at the present time, EAB has not been found in Longmont.

Colorado Department of Agriculture and Colorado State Cooperative Extension recommend that preventative insecticide treatments should begin when EAB has been confirmed within a five (5) mile radius of known infestation location. Therefore, EAB treatment for ash trees in Longmont is not recommended at this time.

Top 5 EAB Tips for Longmont Residents

  1. Determine now if you have any ash trees and, if so, start planning. If you have an ash tree, first decide if the tree is really worth saving. Does the overall health of the tree merit treatment? If you aren’t sure, contact a certified arborist.
  2. Recognize signs of EAB infestation. Property owners with ash trees should be on the lookout for thinning of upper branches and twigs, loss of leaves, D-shaped 1/8-inch holes on the bark, vertical bark splitting or increased woodpecker activity. Report suspect trees to City of Longmont Forestry Services at 303-651-8416 or
  3. Be aware of EAB imposters. Other insects like lilac/ash borer, ash bark beetle and flat-headed appletree borer may look like EAB or cause similar tree symptoms. The Colorado Department of Agriculture is an excellent source for more information; visit their EAB website at
  4. Know when treatments are (and aren’t) a good option. Colorado State University recommends that treatments are only needed within a 5 mile range from a positive EAB detection. Currently, the only confirmed Colorado detection has been in Boulder. Since early detection is difficult, property owners with ash trees have the option to apply chemical treatments to protect high value trees. At the present time, City of Longmont Forestry Services does not plan to apply chemical treatments to public ash trees. We will continue to look for evidence of EAB in Longmont and share updates with residents.
  5. Prevent further spread of EAB. Please don’t transport ash firewood, or any other untreated ash wood products, to other locations. Boulder County is now under a federal EAB quarantine, allowing for stiff fines for those who move untreated wood from the area.

Additional Resourcestrap tree


April 28, 2014 - Emerald Ash Borer: What Front Range, Northeast Colorado Communities Need to Know

April 15, 2014 - Emerald Ash Borers and Commercial Pesticide Application Companies

November 12, 2013 - Emergency Quarantine Issued to Protect Colorado Ash Trees


Colorado Deprtment of Agriculture - Emerald Ash Borer



emerald ash borer on penny