A Low-Tech Mosquito Deterrent
By WILLIAM J. BROAD
Over the Fourth of July holiday, my wife and I joined some friends for a barbecue in their backyard. The guests were lively and the space was lovely — grassy and open but shady and surrounded by lots of shrubs and trees.
In other words, it was perfect for mosquitoes — and indeed, closer inspection showed that they were thriving in all that greenery.
But our friends had come up with a solution that saved us from having to deal with bug repellents or, worse, bites and itches.
On a low table, they set up a small electric fan, perhaps 12 inches high, that swept back and forth, sending a gentle breeze across the grassy area where people were sitting.
That was it. No citronella candles, no bug zappers, no DEET, nothing expensive or high-tech. Yet amazingly, it worked. As far as I could tell, no mosquitoes flew into the vicinity of the simulated wind; nobody was bitten.
As we left, I asked our hosts about the fan idea; they credited a mutual friend at the barbecue. He, in turn, paid tribute to a friend of his: Frank Swift, president of Swift Food Equipment Inc. in Philadelphia.
So I reached out to Mr. Swift, who replied by e-mail. “The solution came from trying to think like a bug,” he explained, “and realizing I don’t like flying into a 15 m.p.h. wind.”
Outsmarting bugs with a fan may be a poorly known strategy. But the method, it turns out, is endorsed by the American Mosquito Control Association, a nonprofit group based in Mount Laurel, N.J., that publishes a journal bearing its name.
“Mosquitoes are relatively weak fliers,” it says on its Web site, “so placing a large fan on your deck can provide a low-tech solution.” The group says mosquitoes fly slowly — from roughly 1 to 1.5 miles per hour, depending on the species.
Scientists have identified another factor. The breeze from a fan disperses the human emanations that allow female mosquitoes to zero in on us. (The guys are innocent! Honest! Females need the stolen blood for egg making.)
Humans exhale lots of carbon dioxide — the most widely recognized of the many likely mosquito attractants, including body heat and odors. When a female mosquito senses the invisible gas, she typically flies a zigzag path within the plume to track down its source.
In a wetland swarming with mosquitoes, entomologists from Michigan State University did an experiment that demonstrated not only the attractive power of a carbon dioxide trap but the effectiveness of plume disruption.
“Fan-generated wind strongly reduced the mosquito catches,” the scientists wrote in The Journal of Medical Entomology. “We recommend that fan-generated wind should be pursued as a practical means of protecting humans or pets from mosquitoes in the backyard setting.”
The recommendation has penetrated the blogosphere — a bit. “Sit near an electric fan while you are outside,” eHow.com advises. “An oscillating fan works best, but a regular box fan will do. Mosquitoes aren’t strong enough to fly through the wind.”
In my experience, that kind of homey advice is lost amid all the ads and pitches for mosquito repellents and traps, which can cost hundreds of dollars.
As for other popular remedies, the mosquito control association says repellent-infused mosquito coils provide only “some protection” at best, and it dismisses the candles with a shrug, saying their mild repellent action offers no significant advantage over other candles that give off lots of smoke.
By contrast, the simple fan seems like a sure thing. In the world of journalism, we call this news you can use.
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