Standards set for aerial mosquito eradication

city council

A panel of Moorhead residents has come up with a decision-making tool to establish when the city will permit aerial spraying for mosquitoes.

The city council approved the decision matrix Monday after a review of the proposed standards by Department of Public Works director Steve Iverson. Modeled on a policy enforced by California, the plan considers a variety of factors – including temperature, rainfall, the numbers of disease-carrying species showing up in traps, the number of West Nile Virus-carrying individuals in those traps, and the number of human infections – in signaling a public health emergency that justifies the aerial application of insecticide. A combined score of 4.1 on the five-point scale will be the trigger.

The council’s approval – on a roll-call vote of 7 to 1, with Chuck Hendrickson dissenting – comes in the wake of a sometimes-contentious discussion last May when the city renewed its ongoing six-year-old contract with Cass County Vector Control to fight the summer scourge. Council members were reacting in part to the widespread death of Monarch butterflies in August 2019 following an aerial application throughout Cass County and over Moorhead.

Moorhead ultimately renewed its contract with Vector Control for the great majority of its services to eliminate mosquito larva and truck spraying on the ground. It withheld the aerial service. After another month of study, the city paid a retainer to the aviation firm. It entailed a change from past years: It did not endorse automatically going along with Vector Control’s decisions on when to engage the contractor, Airborne Custom Spraying of Halstad, Minnesota. Instead, while the city paid the firm’s annual retainer to insure those services would be available in an emergency, it added provisions for flying only after dusk, when beneficial insects are less active; using a less potent formulation of the insecticide permethrin; and developing a more nuanced approach to when public health considerations prompt its application.

Iverson was reporting on that final request. After reaching out to about 15 individuals who have contacted the city with their concerns, he was able to establish a pool of five as his aerial application advisory committee. Members include council member Steve Lindaas; Dr. Alison Wallace, chair of the Department of Biosciences at MSUM; Noell Harden, who has an MS in agroecology and works with University of Minnesota Extension; Dr. Chris Merkord of MSUM’s Biosciences Department, who helped develop South Dakota’s vector control model; and Joe Allen, retired mechanical/manufacturing engineer and now a seasonal employee with Public Works’ Park Maintenance Division. Cass Vector Control director Ben Prather also worked closely with the committee.

The committee met six times, reviewing vector control policies and practices in California, South Dakota, Colorado and the Twin Cities. “This goes far beyond trap counts,” Iverson said. “It uses solid, reliable data already being collected by Vector Control to take all the factors into consideration.”

“The decision on aerial spraying will not be a matter of nuisance control,” Lindaas emphasized. “The final decision will be based on public health concerns.”  

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