Mosquito busters for your backyard

27 08 2007

It’s summertime, and the livin’ is … buggy. In much of the country, Swat Season is in full swing, and the shelves sag with products that claim to help you survive in comfort.  Unfortunately, most of these items are little better than the pests they purport to defeat, homing in on your desperation like a female skeeter chasing carbon dioxide.

We asked some of the nation’s foremost mosquito experts to evaluate the claims of popular products now available. You may be surprised at what truly delivers relief.

First, give yourself a fighting chanceWhen it comes to dealing with mosquitoes, the best defense is a good offense, experts say. That means removing mosquito-friendly habitat from your yard. Here’s what to do:  

Tip and toss. Mosquito larvae need to float atop still water in order to grow and hatch. So don’t let water pool in flowerpot saucers or pet dishes for more than two days, advises the American Mosquito Control Association. Toss tin cans, old tires, buckets, unused plastic swimming pools and other containers that collect and hold water. Clean rain gutters. Change the water in birdbaths and wading pools at least once a week.

Think like a mosquito. After the obvious spots, look for random places that hold water: plastic or canvas tarps used to cover boats or pools, and even places like broad-leaf plants. Got wet spots in your yard? Plant vegetation that likes “wet feet,” advises Marina D’Abreau, horticulture agent for the Hillsborough County (Fla.) Cooperative Extension Service.

Check the deck. The dark area under backyard decks is often moist — perfect for growing skeeters. Dry it out by putting sand under the deck.

Attack! Finally, take the fight to the little buggers. Stock ornamental pools with small, top-feeding minnows called mosquito fish, advises the AMCA. Another effective and perfectly safe option is to sprinkle BT (bacillus thuringiensus) in standing water, such as swimming pools or fish ponds. “Basically, it’s a naturally occurring bacteria that attacks mosquito larvae,” says D’Abreau. BT can be bought at home-and-garden stores in granule form or as so-called “dunks,” which look like “spoiled little rotten green doughnuts,” D’Abreau says. Best of all, she says, it’s not toxic to humans or animals. 

Or, try a new method of larval control: the LarvaSonic, which transmits sound waves into water at the resonant frequency of the mosquito larvae air bladders, rupturing the internal tissue and causing death, according to the company.

If you’ve taken these steps and you’re still being swarmed, you’ll likely want reinforcements. Just be careful which products you turn to, as they vary from completely benign (both to you and the mosquitoes) to potentially harmful for humans. Here’s our experts’ assessment of common strategies and products:


Alas, some of the more exciting strategies offer the least relief.

Strategy: Bug zappers

Examples: Products from perhaps 30 manufacturers, including Stinger, Sunbeam and John Deere. 

How it works, in theory: Most of these devices rely on an ultraviolet light to lure insects to an electrified wire grid where they’re fried, sometimes noisily. 

Toxicity: Safe to humans.

Cost: $30 to $70

Effectiveness: A lot of sizzle, but no steak. Despite the huge popularity of these devices, studies have shown they’re terrible at eliminating mosquito populations; only about one-quarter of 1% of the insects zapped were actually biting bugs. Most of the killed insects were beneficial. And trapping surveys have shown no significant difference between the number of mosquitoes in zapper-equipped yards and those without.

Strategy: Home misting systems

Examples: Mosquito Management Systems, MosquitoNix

How they work, in theory: A collection of misting nozzles connected by tubing are arrayed along the eaves of a house, fence lines or deck railings. The tube connects to a reservoir — usually a 55-gallon drum — of pesticide. Often it’s pyrethrin, a biodegradable insecticide made from chrysanthemum root. The system is set to a timer, spraying morning and evening and killing any insects it touches.

Toxicity: Though the manufacturers tout the fact that pyrethrin quickly biodegrades and the risk of toxicity is low when using recommended insecticides, there are questions about them. According to the federal Environmental Protection Agency, the systems likely don’t pose harm when used as expected, but “excessive use or accidents may pose risks.”

Wary experts include Roxanne Connelly, an associate professor and extension medical entomologist at the University of Florida, who’s on the board of directors of the American Mosquito Control Association. One reason is that a homeowner easily can override the system by punching a button to apply more spray — “and a lot of homeowners’ sense is that the more, the better,” says Connelly.

The group Beyond Pesticides also thinks these systems are a bad idea, pointing out that pyrethroids “have been shown to be respiratory allergens, and use of them may result in asthma-like symptoms, especially in children with a history of asthma or allergies.”

Given some of these concerns, the state of New York has banned the systems, and the EPA is reportedly taking a deeper look at them. 

Cost: Varies. A basic system, with 25 nozzles, runs about $2,500.

Effectiveness: Like bug zappers, misters are an indiscriminate killer.”They’re not recommended by professional entomologists for the main reason that they don’t conform to the concept of pest management,” says Charles Apperson, a professor of entomology at North Carolina State University who specializes principally in the behavior of mosquitoes and ticks. Pest management, he explains, involves targeting a pest. “Unless you knew there were mosquitoes out there, why would you spray? Because it’s (also) going to kill bees and butterflies, and predacious insects and what we call non-target insects,” he says.

Do these systems provide humans relief? Experts say they aren’t aware of any studies that have been done. The insecticide has to land on mosquitoes to kill them, which means it will be effective for only a short period. And then what’s to stop the mosquitoes in the Johnsons’ yard from sniffing you and buzzing over 15 minutes later?

Strategy: Ultrasonic mosquito repellents   

Example: Sunbeam CM160 Electronic Mosquito Repeller

How it works, in theory: Appearing everywhere from supermarket checkout aisles to high-end catalogs, these devices (worn around a wrist, the neck or at the waist) often claim to mimic a sound — the wing beat of the predatory dragonfly, bat vocalizations, male mosquitoes — that the female mosquito supposedly is fearful of.

Toxicity: Harmless to humans, except their pocketbooks.

Cost: $10 to $100

Effectiveness: “They’re probably one of the biggest rip-offs,” says Jonathan Day, a professor of medical entomology at the University of Florida. He says versions have been around for decades, and none of the sonic devices he has tested repel mosquitoes. “In fact,” Day has written, “it is not uncommon for a female mosquito to land directly on the sonic device and attempt to probe.”


So-called mosquito attracters and many of the citronella-based products fall shy of outright rip-offs, though they offer only limited relief.

Strategy: Citronella smoke

Examples:  Citronella torches or candles, such as these from Off!

How it works, in theory: Citronella oil is somewhat of an irritant to mosquitoes, and mosquitoes also don’t like smoke. (That’s why Dad never got bit while puffing on a big stogie.) Put ’em together and you keep away mosquitoes.

Toxicity: Negligible when used as intended.

Cost: $2 to $11

Effectiveness: Not so good. “The studies have shown that it’s not a true repellent,” Connelly says. (That goes for citronella-oil bug lotions, too. The longest time span that passed before a mosquito landed on a citronella-slathered arm was about nine minutes, Connelly says. Compare that to the best repellent, DEET, which keeps mosquitoes off for five hours.)

However, the smoke from citronella candles and the like may annoy the mosquitoes more than the citronella oil itself. So using the candles in a semi-enclosed area — a pool deck or a patio that has walls on two sides — has a chance of working, Day says.

Strategy: CO2-expelling devices

Examples: Mosquito Magnet, Mega-Catch

How they work, in theory: The carbon dioxide humans breathe out is a major attracter of female mosquitoes. These traps usually use propane fuel to slowly release CO2 (some also incorporate lights and smells to try to better mimic humans). When the mosquito draws close, a fan sucks it into a trap, where it dries out and dies. 

Toxicity: Safe — most expel CO2 and water vapor.

Cost: $300 to $1,400 

Effectiveness: “They do collect mosquitoes; that is a fact,” says Connelly. Whether they work depends on the homeowner’s expectations. “If the tolerance level is zero, then they’re not going to give them that.”

The problem is that large batches of mosquitoes tend to hatch all at once, and “these things can’t capture them all,” says Day. So, even if a machine captures dozens, would you notice any difference? “That is the question. And in general, you would not,” he says.

The machines may help if you have a gutter that’s blocked or other constant sources of mosquitoes, Day says. But maybe you’re just attracting more. After all, now the mosquitoes think there’s a big breathing prey to feast on.


So what’s a would-be barbecuer to do, other than retreat indoors?

Slather on the good stuff. If you’re going to be outside for a while, use a bug repellent that contains DEET. “DEET is the gold standard” among repellents, says Connelly, and it has a good safety record if not ingested. True, DEET can melt some synthetic clothing. And it can feel a little greasy. But some newer products come in a more wearer-friendly form, such as a talcumlike powder, says Apperson.

But if you’ve got too many bad DEET memories from Boy Scout camp, look for products containing a new chemical called Picaridin, which works just about as well, says Connelly. One such product is Cutter Advanced with Picaridin.

Harness the wind. A simple but effective strategy for people sitting outside (say, on a pool deck) is to place a large fan so that it blows across the deck, says Day. “Any wind speed of over 1 mph will disrupt mosquito and biting midge flight.”

Fight the smart fight. If you do have some devices, such as an attracter, the experts say using them smartly can help:

  • Don’t wait until an hour before the party to turn on the devices. “They work better if you turn them on three, four days” before your barbecue, advises Daniel Kline, a research entomologist with the U.S. Department of Agriculture.
  • Situate the device between you and your enemy to best intercept it — and the closer to where mosquitoes are emerging, the better.
  • An old entomologist joke goes, “What do you do if you’re given a mosquito attracter? Put it in your neighbor’s yard.” This has a kernel of wisdom to it. Put an attracter far enough away so that if it works at all, it will pull the insects away from you, not bring them to you. And if you’ve already invested in a few propane-spewers, for example, arrange them in a defensive perimeter — don’t stand next to them.

By Christopher Solomon




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