Moorhead vs. Mosquitoes – We’re Winning (So Far)

Paul Fiechtner                                                                             Ben Prather
Public Works Director                                                               Cass County Vector Control

Nancy Edmonds Hanson

It’s a battle as old as summer – humans versus mosquitoes. So far, say the men heading the local fight, the Fargo-Moorhead community appears to be winning.
But the summer is young, and hot, humid days lie ahead.
So far, the cooler-than-expected temperatures of spring and early summer have offset the irksome swarms typically encouraged by frequent rains and lots of standing water. “Cold weather slows down the activity,” Moorhead public works director Paul Fiechtner observed Monday. “Other than a spike in numbers on June 13 that quickly dropped back to tolerable levels, we’ve been doing pretty well.”
But in typical Upper Midwestern style, he adds, “My guess is that warm weather and more rain events mean that we’ll soon see a rising hatch.”
Fighting the onslaught of biting bugs is an annual challenge for the Department of Public Works. Allied with Cass County Vector Control, the Moorhead agency keeps an eye on the population of the annoying insects and stands ready to assault them when the tide rises beyond a tolerable level.
Moorhead has contracted for many years with Cass County Vector Control. Headed for 15 years by Ben Prather, the neighboring agency provides intelligence for the fight: First, by hunting and treating mosquito larvae before they can turn into biting adults, and second, by trapping adults and analyzing their numbers. If the population peaks and reaches full strength, Vector Control advises Fiechtner’s department that it may be time to spray.
So far, that hasn’t happened this summer. As of Monday, the companies with which the city contracts for either ground-mounted trucks or aerial spraying remained idle, as they did throughout the summer of 2023. Whether they’ll soon get busy, it seems, is in the hands of Mother Nature.
The city has a say as well. According to an ordinance passed in 2021, recommendations by Vector Control are closely reviewed by Public Works before action is taken. Public concern about application of airborne insecticide peaked the year before, in 2020, when spraying coincided with the migration of butterflies and other pollinators. The so-called Monarch Massacre created a groundswell of objections from area residents.
Fiechtner says his office still gets calls from the public. “They’re about equally worried about mosquitoes and about pollinators,” he reports.
Like most communities, Moorhead uses a chemical called permethrin to combat mosquitoes. The man-made chemical mimics one that occurs naturally in chrysanthemums. It’s toxic to all flying insects, but considered generally safe for humans at the low level of exposure resulting from spraying.
“The problem is that it kills all flying insects. It’s not selective,” he explains. When Vector Control’s mosquito numbers are high enough to warrant action, he explains, “We only spray between 8 p.m. and midnight, when mosquitoes are most active but the bees and butterflies are tucked in for the night.”
Vector Control director Prather credits his agency’s assault on mosquito larvae for the generally low numbers of biters prevailing at the moment. “We’re doing pretty well. We were expecting to get hit with a real wave earlier in June, but it’s actually been kind of ho-hum.” He adds, “No news is good news.”
Frequent rains have meant plenty of standing water – a red flag for outbreaks. But Vector Control’s crews have patrolled the area since May – including Moorhead – to prevent the infant mosquitoes that hatch there from growing up to be pests. Its weapon is Bti (Bacillus thuringiensis israelensis), a naturally occurring bacterium that produces toxins that specifically target and only affect the larvae of the mosquito, black fly and fungus gnat.
The agency keeps track of the number and kind of mosquitoes who manage to mature with trapping throughout the season. Not all prey on humans, after all; some prefer deer, cattle, bison, birds or reptiles. Those creatures are on their own.
Instead, the focus is especially on three of the dozen species with a taste for humans: Aedes vexan, most active at dusk and dawn and frequently found in standing floodwater; Aedes dorsalis, the more aggressive variety that bites during the day; and Culex tarsalus, the primary driver of West Nile Virus. “We start testing for the virus in mid-July,” Prather notes. “So far, we’ve found no indication of activity.”
The Cass County agency keeps a running count of the number of adults found in its traps. The current level across the metro – 38.8 per trap as of Tuesday – is barely above the “nuisance level” of 36, not nearly enough to trigger a recommendation for truck-based or aerial spraying.
While the weather ultimately controls the local swarms, Fiechtner points to the four D’s published on the city’s website. The common-sense measures, he says, go a long way to moderate the flying biters’ body count:
Drain: Mosquitoes breed in water. Drain any standing water in your yard each week. Bird baths, clogged gutters and kiddie pools are common breeding sites.
Dress: Wear lightweight, long-sleeved shirts and long pants while outdoors. Spray clothing with insect repellent, since mosquitoes may bite through clothing.
Defend: Apply insect repellent sparingly to exposed skin. Use an approved repellent according to its label.
Dawn/Dusk: Limit time spent outdoors at dusk through dawn, when mosquitoes are most active and feeding.

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