Does “carpet bomb” spray extra on mosquitoes than on well being? Mass butterfly deaths gas the dialogue


Heavy rains in mid-August created ideal conditions for a large mosquito hatch, which later that month resulted in aerial spraying, resulting in the mass death of monarch butterflies – collateral damage in the fight against the West Nile virus.

Local officials and residents have been debating the Cass County Vector Control’s spray program since the Aug. 26 incident.

Fargo City Commissioner John Strand is not comforted by assurances from vector inspectors and others that the mass extinction of monarch butterflies should not have happened. He fears that the dead monarchs could be a warning, like the “canary in the coal mine”.

“For me this is the moment when I ask questions,” he said. “Are there other unintended consequences, including human health?”

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Strand is calling for a review to see if Cass County’s spraying program is more aggressive than other cities in the area and to investigate the pros and cons of air spraying, which health officials say is an important tool in preventing the West Nile -Virus are.

“Not everyone sprays like us,” said Strand.

Mayor Tim Mahoney, a doctor serving on the vector control panel, agrees with Strand that there should be public discussion of whether or not to stop spraying during the monarch’s migration. The public could be notified to take action and the spraying could be postponed until after the migration, he said.

Mahoney said, “You have to have a lot of dialogue to spray. Everything has to be logged off. “

Mahoney and Strand plan to host a public forum this fall. “Let’s have a discussion,” he said. “We have to try to see if there is another way.”

More than 80% of people infected with West Nile virus never develop symptoms, although others get West Nile fever and a small number – less than 1% – develop neurological problems that lead to serious illness or disease can lead to death, said Ben Schram, West Nile surveillance coordinator for the North Dakota Department of Health.

People are upset about the monarch’s death and want to prevent it from happening again, Strand said. Ben Prather, director of Cass County Vector Control, said the deaths occurred during the migration of the butterflies.

More should be done to monitor migration so that vector control can avoid spraying when the butterflies are most vulnerable, Strand says. He said he had heard from many residents who no longer wanted to see mass victims of butterflies, major pollinators, due to mosquito spraying.


Ron Miller, a retired Fargo pediatrician, has also raised concerns about potential human health consequences and believes that spraying the air with “carpet bombs” to control mosquitoes is unnecessary – more to keep people comfortable outdoors may feel as valid public health reasons.

Individuals should take greater responsibility for keeping mosquitoes and other insects safe, he said. In very small doses, permethrin, the insecticide used by vector control to spray against mosquitoes, repels insects.

“It’s very safe to put it on your clothes,” he said. Or people can use other insect repellants like DEET as directed.

As for airborne permethrin spray, he wonders if we know enough to count on safety. “I don’t think the answer to that is known. It is believed to be safe, ”he said.

Experts once considered another insecticide, DDT, to be safe before it was banned because of widespread harm to birds and other species and concerns for human health.

“No question about it, it works,” Miller said of permethrin. “The problem is, it kills all insects, including butterflies.”

According to Schram and Prather, North Dakota is a state with a high West Nile virus prevalence rate. Airborne spray is a safe and effective way to control mosquitoes and prevent the virus from spreading.

West Nile virus cases in North Dakota vary greatly from year to year. Three cases have been reported so far this year and nine cases last year, but 204 cases were reported in 2018, including 60 with neurological symptoms that can include disorientation, headache, or even paralysis, Schram said.

West Nile virus deaths in North Dakota peaked at five in 2003, with two reported each in 2016 and 2017.

But Miller claims the health risk is exaggerated, citing figures from the North Dakota Department of Health showing that cases are rare in Cass County. There were no cases last year, 16 in 2018, four in 2017, 21 in 2016, and none in 2015.

Also, according to Miller, case reports alone don’t tell the full story, as serious illness from the virus is rare. He argues that fewer cases of mild West Nile virus do not justify spraying and that targeted spraying to protect vulnerable populations, including the elderly, would be a smarter choice.

“It’s like carpet bombardment,” he said of the air spray. “It’s hard to know if a child who plays in an air-sprayed yard will develop an illness later in life.”

Barrels filled with permethrin, an insecticide used in air spraying mosquitoes, are pictured at Cass County Vector Control in West Fargo on Friday September 11th.  Alyssa Goelzer / The Forum

Barrels filled with permethrin, an insecticide used in air spraying mosquitoes, are pictured at Cass County Vector Control in West Fargo on Friday September 11th. Alyssa Goelzer / The Forum

Vector control only uses aerial spraying when the number of mosquito traps is high. According to Prather, two to five applications are common. The number of mosquito traps in recent years is much lower than before, he said.

“We want people to enjoy nature in our short summers,” said Prather.

The first line of defense in mosquito control is to prevent the formation of standing ponds where mosquito larvae hatch. Efforts are focused on clearing pool stains and treating them with larvicides to kill the mosquitoes before they hatch.

Even so, aerial spraying is sometimes required, but officials make an effort to keep it from becoming routine and rely on larvicides to do most of the job, Prather said. Larvicide is “virtually non-toxic even to other insects,” he said.

Even aggressive larvicide treatments can be inundated by heavy rainfall, but that requires aerial spraying, Prather said.

Permethrin, a neurotoxin synthesized in 1977 and first approved for spraying on cotton in 1979, is one of the least toxic insecticides. It is used in agriculture, crop spraying, and livestock protection, and in households, including as an insect fogger.

Cass County Vector Control's Jared Lamirante analyzes and separates mosquitoes collected from traps earlier on Friday September 11th in West Fargo.  Alyssa Goelzer / The Forum

Cass County Vector Control’s Jared Lamirante analyzes and separates mosquitoes collected from traps earlier on Friday September 11th in West Fargo. Alyssa Goelzer / The Forum

One study found no observable effects from permethrin dosages equivalent to a 30-pound dog receiving 1.5 grams daily for three months. In order for a person to ingest a 1.5 gram dose, they must consume all of the permethrin that is sprayed onto an area three-quarters of a soccer field by an ultra-low volume ground fogger, according to Cass County Vector Control.

Lethal doses of permethrin and DEET are lower than common substances like albuterol, simethicone, paracetamol and salicylic acid, the active ingredient in aspirin, according to the World Health Organization’s acceptable daily intake as stated by vector control.

Still, Mahoney said officials had directed Prather to look into less toxic alternatives to permethrin.

Miller is still not happy with the fact that science has shown that even low doses of permethrin are safe over the long term.

“The annals of medical history emit a variety of chemicals that were considered safe at the time,” and later found to be toxic or carcinogenic, he said. “The risks of many chemicals that have been used in this way are really unknown.”

Miller also said it had not been shown whether aerial spraying makes a “significant difference” in preventing severe cases of West Nile virus.

Mahoney, who said Prather presented “research piles” showing permethrin is safe, said the vector control program established in 1988 has popular support.

“In our community, mosquitoes can be a big bane,” he said. Spraying, he said, was “a consolation for the people”.

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