The town of Berthoud, which celebrated 35 years as a “Tree City USA” this Arbor Day, is piloting a $15,000 program to help its residents proactively battle an invasive species bent on destroying a significant portion of the town’s tree canopy.
Ash trees currently comprise about 25 percent of the town’s tree population, according to Town Forester Josh Embrey. The trees are mostly located in what is considered Old Town Berthoud, and all are at risk of a mass die-off due to the emerald ash borer, a destructive, non-native beetle responsible for killing more than 100 million ash trees throughout the United States.
“We’re trying to save as many of these trees as possible,” said Pat Karspeck, vice chair of the Berthoud Tree Advisory Committee. “It’s not the homeowner’s fault; they usually bought the property with 30- to 75-year-old ash trees.”
About 20 Berthoud residents are currently signed up for the anti-emerald ash borer plan, which states the town will split the cost of treating ash trees on private property bordering the street with the residents on whose property the trees reside. Though the application period ended June 15, its creators hope that this pilot group will set the stage for another round of funding next year.
The seven-member Berthoud Tree Advisory Committee came up with the idea for the program as an addendum to the town’s Emerald Ash Borer Strategic Plan, said Karspeck, who is current Berthoud mayor Will Karspeck’s mother.
The emerald ash borer was first detected in Colorado in Boulder in 2013, according to the Colorado Department of Agriculture. It was confirmed in Superior, the fifth Colorado community outside of Boulder, June 26.
Though the beetle has not yet been confirmed in Berthoud, there is a good chance it is already there, undetected, Embrey said. In fact, the hardest part about managing the emerald ash borer is detecting it, he said.
Signs of an infestation, such as a thinning canopy and small D-shaped holes in the bark, do not usually emerge until three or four years after the initial infestation. Maximum infestation occurs after about eight years, at which time the boring beetle can cause trees to become dangerously brittle.
“This is more a proactive program; just because we haven’t detected it doesn’t mean we don’t have it,” Karspeck said. “We’re doing this because we suspect it might be here; once it shows up, it starts popping up everywhere.”
Karspeck, who was a proponent of the program on the Tree Committee, said the town investing in its ash tree canopy is akin to the kind of maintenance a municipality does on other amenities in public spaces, like a fountain in a park or a public pool.
The program is modeled after the Colorado State Forest Service wildfire mitigation program, in which the state agreed to cost-share with homeowners who take it upon themselves to mitigate fire danger near their homes, said former Tree Advisory Committee member John Goreski, who served on the board from 1991 to 2017.
Residents can have up to two ash trees selected by the town forester to receive an injection of emamectin benzoate, an avermectin-derivative insecticide. The town will cover half the cost of each shot of treatment, which per the winning project bid by Boulder-based Blue River Forestry & Tree Care will cost $6 per inch of tree diameter.
Karspeck said she thought the town got an “excellent” price. Dustin Brown, owner of Blue River Forestry & Tree Care, declined to discuss prices in detail but said the treatment industry has gotten ever more competitive since the emerald ash borer was first detected in the state.
Each injection is done by a certified pesticide applicator, who uses a sharp drill bit that makes up to a two-inch-deep hole into the tree. The applicator then inserts a one-way valve to prevent leakage of the pesticide as it is pumped into the tree’s vascular system, said supervising arborist Joshua Rawson with Blue River.
Not all trees are good candidates for treatment, and it is up to Embrey to make the call. Eligible trees are at minimum 15 inches in diameter at breast height, are located near the street and should not be showing signs of decline.
Trees that are small or in poor health are recommended for removal before the beetle eats away at their structural integrity and they become a hazard.
For those who want to cut down any of their ash trees, the town will provide a new tree of a different species and plant it, if the homeowner absorbs the cost of removal.
For residents who wish to treat trees that are otherwise in good shape but that are not located near a public right-of-way, the contract also provides that Blue River will extend the $6-per-inch of diameter price to the person’s other trees as well.
Though some emerald ash borer pesticides contain neonicotinoids, a type of chemical insecticide research has connected to declining bee populations, the type of treatment Blue River will use poses little risk to local bees, said Rawson, who is also an International Society of Arboriculture-certified arborist.
Whitney Cranshaw, a professor and entomologist at Colorado State University, said he, too, considers the risk negligible.
Ash trees are wind-pollinated, and ash tree flowers do not produce nectar — so, any risk to pollinators from the treatment would come from insecticide residues that appear in ash tree pollen collected by bees, Cranshaw wrote in an email to the Reporter-Herald.
A study of pollen collected in Fort Collins, Boulder, Longmont during the two to three weeks when ash was in bloom showed 96.5 percent was collected from other sources than ash, Cranshaw wrote.
“A very small percentage, and the percentage is likely reduced further if one has an abundance of alternative flowering plants available during the period when ash trees flower (sometime between very late March and the end of April),” he wrote. “(My) conclusion is that there is so little potential for significant exposure even under the worst case scenario that it is not a biologically significant risk application to pollinators.”
He recommends that people wishing to help bees consider planting trees, shrubs, bulbs and flowering herbaceous plants that produce early season flowers.
Re-treatment is recommended every two years, Brown said. This may continue for the remainder of the tree’s life, or less — the beetles are only really prevalent for around 10 years after infestation, he said.
“It’s rather expensive, which is why we’re trying to incentivize people to get going on it,” Karspeck said. “They’re goners if you don’t treat them … But again, that (treatment) bill is cheaper than taking down your ash tree, especially if you’ve got a big one.”
The town has already initiated treatment of certain trees in Berthoud public parks. Brown said a schedule for Blue River to begin treating cost-share trees around Berthoud is not yet established.
Though this year’s application period is over, Karspeck and Embrey said they are hoping the pilot year will be a success so it might be funded again next year.
“These ash trees have served our needs for many years,” Karspeck said. “Most are mature or declining, but without emerald ash borers, who knows how many more years they would have… Homeowners really have to start their plan of action, because it’s not if — it’s when.”
Julia Rentsch: 970-699-5404, jrentsch@reporter-herald.com
