Hundreds Of Ash Trees In Boulder Infested With Beetles

BOULDER, CO — An invasive wood-boring beetle is attacking ash trees throughout Boulder and city officials are taking action to make sure the trees don't fall and threaten public safety. The City of Boulder’s Parks and Recreation Department will have multiple contractors pruning or removing trees in city parks and public street rights-of-way over the next several months.

Tree maintenance work began in mid-October and is scheduled through March 2020.

The scope of tree work includes:

• The week of Oct. 14: Six ash trees will be removed on Pearl St Mall. These trees have severely declined in health due to growing in a restricted root zone and are heavily infested with lilac ash borer, ash bark beetle and emerald ash borer, the city said. All removals are scheduled between 6 a.m. and 11 a.m. No street closures will occur as work zones are small and will be coned and taped off for public safety, the city said. These trees will be replaced in spring 2020.
• Oct. 15 to March 31, 2020: The remaining 385 tree removals and non-rotational pruning work is citywide and adjacent property owners will be notified via door hanger at least one month prior to the commencement of work, the city said.
• Starting Jan. 1, 2020: rotational pruning is scheduled to begin in the Mapleton Hill area.

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Of the 418 trees identified for removal, 302 are ash trees heavily infested with the emerald ash borer, Boulder officials said. The remaining 116 non-ash trees are either structurally unsound or are dying and pose a risk to public safety.

Boulder Forestry, a division of the Parks and Recreation Department, monitors about 50,000 public trees. City park and public street trees are inspected periodically for structural integrity and safety using industry-set standards and techniques, officials said.

Forestry staff are conservative when determining whether a tree must be removed, the city said. Factors that go into the risk assessment are tree species, size, defect and what the tree would hit if it fell.

Emerald ash borer, an invasive wood-boring beetle, attacks all North American ash that aren't protected by pesticides. Now present in over 35 other states, the beetles have killed millions of ash trees over the past two decades.

All public and private ash trees in Boulder are currently at risk, the city said. As the beetle populations in Boulder continue to increase, ash trees are expected to die at an accelerated rate, and residents can expect to see growing numbers of ash tree removals citywide on both public and private property over the next several years.

Tree work along public street rights-of-way may require temporary lane closures or traffic detours. Flaggers will be onsite to ensure public safety and to guide pedestrians through work zones. Specific information is posted the week prior to the City Cone Zones map.

Boulder Forestry also manages a Street Tree Planting Program to support environmental sustainability, Boulder's Climate Action Plan goals and the continued vitality of the city’s tree canopy.

Property owners who are interested in having a free tree planted in the public street right-of-way adjacent to their home can visit BoulderForestry.org and click on “Request a Street Tree.”

Residents who are contracting the removal of a tree on their properties are asked to use a tree care company licensed through the City of Boulder. A list of licensed arborists can be found on BoulderForestry.org.