City Forester Bryan McCoy is on the frontlines in the fight against the Emerald ash borer (EAB), a tree pest that has devastated millions of ash trees across North America.
According to McCoy, these invasive insects are highly aggressive, often leading to the death of even healthy trees within two to four years of infestation.
“They move quickly into the ash trees, and they are so aggressive that even healthy trees die within two or four years after being infected,” he explained.
One of the first symptoms of an EAB infestation is the thinning of leaves at the top of the tree.
McCoy highlights that many people overlook this crucial indicator, focusing only on the lower parts of the tree.
“Most are only concerned about what’s going on at eye-level of a tree,” he remarked.
In Westminster alone, there are approximately 69,000 ash trees on private properties, contributing to the 1.2 million ash trees estimated in the Denver-metro area.
Since 2013, the city has been analyzing its city-owned ash trees for treatment.
With about one out of every seven trees in Westminster being an ash, the city completed a tree inventory in 2023, specifically targeting ash trees in Right-of-Way locations.
The assessment revealed that 3,174 ash trees could be preserved through treatment.
The city emphasizes that ash trees not meeting treatment criteria must be removed to prevent the spread of EAB and minimize risks to tree workers.
Removing untreated trees early allows for faster replanting efforts by establishing prioritized locations for new trees.
Between July and September 2023, the city treated eligible trees using a micro-injection system to deliver the treatment directly into the tree trunk.
However, McCoy pointed out that the city lacks sufficient personnel to manage the removal of infected trees on private property.
He urges property owners to consider replacing their ash trees with different species to combat the spread of the Emerald ash borer.
“The ash borer only infests that ash tree,” he noted, encouraging the planting of alternative tree species.
To assist residents in selecting new trees, the Colorado Department of Agriculture provides a database of registered nurseries and landscape contractors.
The Emerald ash borer is originally from Asia and made its way to North America in the 1990s, likely through ash wood pallets or packing materials.
Since its discovery in southeastern Michigan in 2002, it has wreaked havoc across the central and northeastern United States and Canada.
The first Colorado detection of EAB occurred in September 2013 in the City of Boulder.
Currently, approximately 15 percent of trees in Colorado’s urban forests are ash, making EAB a significant threat to urban forestry statewide.
As EAB continues to spread along the Front Range, Thornton recently became the first city east of Interstate 25 to confirm an infestation.
Additionally, McCoy mentioned that EAB has been detected in Oregon as well.
On a recent day, McCoy observed clear signs of EAB infestation behind businesses along Sheridan Boulevard.
The presence of numerous round holes in the bark of the ash trees indicated that the insects were actively feeding on the trees.
Despite their popularity for providing shade and aesthetic fall colors, McCoy fears that many of the ash trees near Sheridan may not survive.
“It’s sad,” he lamented, acknowledging the impending loss of these once-vibrant trees.
image source from：coloradocommunitymedia
