Fargo-Moorhead's 'monarch massacre' starts national dialogue

Unfortunately, in one of the only clues to why so many butterflies died, the aerial spraying Aug. 26 occurred while the monarchs were migrating.

Dead Monarch Butterflies
Dead monarch butterflies were found across the Fargo area after aerial spraying in August 2020 to control mosquitoes. WDAY photo

FARGO — If there's one thing that has developed in the six months since what's been called the "monarch massacre" that followed an aerial mosquito spraying in the Fargo-Moorhead metro, it's that there's a national dialogue underway.

In the first of two informational meetings at Fargo City Hall on how the agency operates, Cass County Vector Control Director Ben Prather said the U.S. Fish and Wildlife Service, American Mosquito Control Association and butterfly advocacy organizations are talking for the first time.

Are there any definite answers on why the perhaps "freak coincidence" occurred with endangered butterflies dying in the hundreds across the metro after the aerial spraying?

Prather said "no," but in his hourlong presentation on Thursday, Feb. 18, at Fargo City Hall he wanted people to know that his agency puts a "ton of thought and diligence into spraying decisions."


He also made it clear that hundreds if not thousands of cities and districts across North America use the same insecticide — permethrin — in their spraying efforts. There's ongoing work building on decades of research regarding the safety of the chemical that's also used in crop production and household products with approval from the federal Environmental Protection Agency and the Food and Drug Administration, he said.

After the meeting aerial spraying company owner Rob Aslesen, of Airborne Custom Spraying of Halstad, Minn., said he has been running his operation for decades and that the same week in late August when the monarchs died here he had sprayed 14 other cities in the region with no reports of any butterflies dying.

He also recalled hearing of only one other instance about 20 years ago where there was a report of any butterflies dying after spraying, and that was a smaller situation in southern Minnesota.

Aslesen said people "smarter" than Prather and himself on the national level are continuing to look into the issue, however.

During the meeting, there were three email questions for Prather and Fargo Public Works Director Ben Dow with one person speaking in person.

The email questions centered on the human and wildlife safety of the insecticide and why any spraying was being done, as many cities don't undertake any efforts.

Prather said for some cities it's "not a matter of need but finances," as other cities don' t have the resources to set up an operation.


He also emphasized that his agency spends 90% of its staff time and finances on controlling larvae in ditches and other standing water in a 200-square-mile metro area. Spraying, he added, doesn't make sense in the rural parts of the county with its wide open fields and sparse population.

Prather also said 60% of mosquito control products are used in controlling larvae, with 29% used in aerial spraying. Truck spraying uses 5% of the product while backpacks in more sheltered areas where his staff drives all-terrain vehicles use 3%.

He presented figures from June 15 to Sept. 15 of 2020 when there were 76 days with no applications to control the hatched adult females that bite, with 4 days of truck spraying on city streets and 3 days of aerial spraying.

During the past five years, there were 503 days with no adult mosquito spraying, 28 truck days and 21 aerial sprays.

Unfortunately, in one of the only clues to why so many butterflies died, the aerial spraying Aug. 26 occurred while the monarchs were migrating.

The season of the monarch migrations, Prather said, is anywhere from Aug. 10 to Sept. 20.

Another reason for the aerial spraying last year on that date was that numbers in traps in the metro were at historically high, if not at record levels, after the rare heavy August rain. Much of Prather's seasonal staff who are college students had already left, he said, leaving his department without enough help to do truck spraying instead.

As for the reason for doing any spraying at all, besides the nuisance factor of the pesky bugs, it's to control the sometimes deadly West Nile virus.


The lone speaker in person on Thursday was Bridgette Readel, of Hunter, who said while holding a photo of her family that someone was missing.

It was her father, who died of West Nile virus at age 58.

She described the pain of his hospitalization for six months after being bit by a mosquito while harvesting wheat. She said her father suffered a heart attack, stroke and serious breathing and swallowing difficulties during that time.

Readel said her father, who was facing the rest of his life on a feeding tube and respirator, decided to end his life support.

"I want to see the spraying continue using the best management practices," she said. "It can save lives."

The next informational meeting on vector control and the butterfly massacre is scheduled for March 3 in City Hall.

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