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City arborist reports surfactant may extend emerald ash borer control to two years; city wins 31st Tree City USA award
Summary
City staff told the Tree and Stormwater Advisory Board that adding a surfactant to ash borer treatments appears to extend control from one year to two, potentially reducing costs or expanding coverage; staff also announced the city's 31st consecutive Tree City USA designation and a $1,000 grant for Centennial Park plantings.
The city's arborist told the Tree and Stormwater Advisory Board on Wednesday that adding a surfactant to the insecticide mix for emerald ash borer treatments appears to extend control from one year to two, a development that could either allow the city to treat twice as many trees on an alternating schedule or to halve chemical costs by treating the same trees every other year.
"What we're finding is people are getting a two-year control instead of a one-year control," said the arborist. He said staff will continue to gather data before changing long-term treatment schedules.
The report came amid other positive items: staff said the city was recognized for its 31st consecutive year as a Tree City USA and that the city received a $1,000 Mid-American Trees Please grant to plant trees along the south trail in Centennial Park. Arbor Day was observed April 24, staff said.
Why it matters: extending the residual control of a systemic treatment reduces the frequency of application, which could lower per-tree costs or stretch limited staff capacity and budget dollars. The arborist said he currently treats about 47 mature ash trees across the city, including a 35-inch legacy ash near the playground at Pen Meadows Park that the city is trying to preserve.
Staff provided additional technical and cost context. The product the crew currently uses is Safari; imidacloprid was cited as an alternative with a shorter documented residual. The arborist described the treatment as systemic (taken up through the roots and wood so feeding insects ingest it) and noted that when a treated tree is the only live ash in a heavily infested area, insect feeding and subsequent die-off can still cause visible tree damage as the system takes effect. He estimated a per-tree application cost in the neighborhood of $10–$15 and said a 200-gallon tank mix costs a few hundred dollars, though he recommended asking budget staff for precise figures.
The arborist also described recent volunteer and educational activity: students from Heritage Christian School participated in a service day on May 8 removing invasive honeysuckle and mulching trails; clearing revealed many young ash saplings (about 5–6 feet tall) sprouting from seed produced by dying canopy trees. He said saplings in timbered areas are difficult to treat and will largely be left untreated for now.
On training, the arborist said he attended the Shade Tree Short Course in Ames and passed the Certified Arborist exam. "I am now a certified arborist," he said.
Staff advised homeowners that some insecticide products require certified applicators, but homeowners applying to their own trees may be legally allowed to do so. The arborist said the city can offer guidance on products and application methods but does not provide homeowner treatments.
The board did not take formal policy action on treatments at the meeting; staff said they will continue monitoring results and report back. The meeting adjourned following routine minutes approval and scheduling; the next meeting was listed for Aug. 12, 2026 at 7:00 p.m.
