MOORHEAD, Minn. — After last summer's mass die-off of monarch butterflies, Moorhead is opting out of aerial spraying for mosquitoes this year — at least for now.

The City Council voted 6-1 Monday, April 26, to sign a contract with Cass County Vector Control for other mosquito control measures but opt out of spraying. As part of the vote, the council members asked Public Works Director Steve Iverson to investigate the issues surrounding aerial spraying for mosquitoes.

At a future meeting, the City Council may vote to raise the threshold for spraying in the city or to cease spraying altogether.

The issue of aerial spraying has been a hot topic in the metro since last August when a mass die-off of monarch butterflies, which some called the "monarch massacre," occurred in the Fargo-Moorhead area after aerial spraying.

It's believed the spraying may have coincided with the annual monarch migration that some believe occurs in the area from about Aug. 25 to about Sept. 5.

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Iverson said 95% of Vector Control's work is putting larvicide into standing water to kill mosquito larvae, so spraying was a small part of the contract that also includes Fargo, Horace and Cass County. Ground spraying by truck is still included in the contract.

The aerial spraying occurs two to four times a year and doesn't usually start until July.

Council member Laura Caroon said she thought spraying after dark would minimize the number of people who may be outdoors. She suggested better communication when spraying occurs so people concerned about health issues could be alerted.

However, council member Chuck Hendrickson, the only vote to keep spraying in the contract, said the mosquitoes were so bad last August that "you couldn't go out of the house, and after spraying the bugs disappeared." He added he knew family and friends who had West Nile and that it was a "terrible, terrible crippling disease."

The council voted to have Iverson, who said he favored keeping spraying in the "tool box" to control mosquitoes and West Nile, research how other cities control mosquitoes and potential higher thresholds to hit before spraying is done.

The discussion is expected to continue in two weeks at the next City Council meeting, as Iverson said he would prioritize the research.

The council members wanted to make sure they could add the aerial spraying back in after further research or if there was a serious concern about West Nile this summer.

It wasn't clear how the contract would work with Moorhead pulling out of the spraying, so that will also be part of Iverson's investigation.