Before the first frost came around and took out lots of insects, local health departments have been trying to prevent West Nile virus in humans by eradicating mosquitos. But the methods they use – such as mosquito fogging – have the potential to impact other wildlife such as pollinator insects.
What is West Nile virus?
West Nile virus is a mosquito-borne disease found in Ohio. This year, Clark County detected 74 mosquitos infected with West Nile Virus. And Montgomery County detected seven mosquitos with West Nile.
West Nile can cause headaches, body aches, joint pains and vomiting if humans become infected. In rare cases, the virus can cause serious brain swelling.
To combat infection in humans, county health departments across the state use mosquito fogs. Reed Johnson, an entomology professor at Ohio State University’s Wooster campus, said mosquito fogs – which can kill all other insects they come into contact with – are often used for public health reasons.
“Unfortunately, the pollinators have to take a backseat to human health because some of these diseases are really no joke,” he said.
Why should we care about pollinator insects?
Pollinator insects include butterflies, bees, moths and more. Pollinators are considered an important species because they balance out the food web and help flowering plants reproduce. That’s why there’s a specific way pesticide products should be used.
Johnson said in order to reduce impacts on non-target pollinator species, the pesticides should be used between the hours of dusk and dawn. This gives an opportunity for the chemicals to dissipate in the environment and targets mosquitos at the height of their activity – while the pollinators are away.
And not all pesticides are the same. Montgomery County and Clark County both use the same product for treatment called Duet, which belongs to a broad category of pesticides called pyrethroid insecticides.
“The good thing is these (types of pesticides) do break down relatively rapidly in the environment when they are exposed to sunlight. So the UV light from the sun will break these pyrethroids down. And so they are not really long lasting,” Johnson said. “They'll break down and will become less toxic to any insect that encounters them.”
While also being capable of killing any insect, it also contains an attractant for mosquitoes. Pyrethroid insecticides mimic the natural insecticide found in chrysanthemum flowers, Johnson said.
“That's the one of the reasons why we choose that particular product, because it has a lower impact on (wildlife) that we're not trying to affect like pollinators,” said Jason Turner, senior manager in environmental services for Public Health - Dayton & Montgomery County.
Are there other options to fight the spread of West Nile?
But Elizabeth DeWitt, director of environmental health with Clark County Combined Health District, said mosquito fogs are perhaps the least effective method the county uses.
“Because it is not long lasting, it stays in the air for just a short amount of time, and it only kills mosquitoes that fly through at that time of application,” DeWitt said.
Other methods that the counties use include spraying larvicides, which kills the mosquitos before they mature, and reducing areas of standing water to reduce reproduction. DeWitt said the amount of water in a bottle cap is enough for thousands of mosquitoes to breed.
Luckily there have been no West Nile virus detections in humans in Clark or Montgomery counties in 2024.
