Should you trap or zap?

A repellent may work on the person wearing it, but what if you want to
ban mosquitoes from a whole area, so, say, they won't crash your
backyard barbecue? Bug zappers, the ultraviolet-light devices that
slay insects with a reassuring "zot!" are one option. In our tests,
however, a zapper killed barely more mosquitoes than lodged on a
nearby piece of sticky paper.
A newer choice: traps that lure and capture mosquitoes by mimicking
mammals. The three widely sold traps we tested were not a cure-all.
Although they were far more effective than the zapper at removing
mosquitoes we released into a lab room, they didn't eliminate all of
them. A species that carries West Nile virus was only moderately
attracted.

In the end, we had to agree with Ray Parsons, director of mosquito
control for Harris County, Texas, site of a large West Nile virus
outbreak. "They do pull in lots of mosquitoes," Parsons told us, "but
people shouldn't expect them to reduce the potential of disease
transmission completely."

How they work. Traps mimic factors that make people irresistible to
mosquitoes: exhalations, odors, body heat, or sound. Once they've
lured the bugs--from a claimed area of 3/4 acre or 1 acre, depending
on the model--they use either suction or sticky paper to capture them.
The traps we tested must be plugged into an electrical outlet, and
manufacturers advise using them around the clock during mosquito
season, rain or shine.

The American Biophysics Mosquito Magnet Liberty, $500, and the Lentek
Mosquito Trap MK01, $325, generate carbon dioxide and warmth by
burning propane from a standard 20-pound tank that must be purchased
separately. The Magnet Liberty also includes a cartridge of octenol, a
chemical attractant said to smell--to a hungry mosquito, at
least--like cow's breath. Both traps have fans that suck approaching
mosquitoes into a mesh bag or cup, where they stay because they can't
fly "upwind." (They then dehydrate and die.) The Magnet Liberty's
fine-mesh bag should also capture no-see-ums and other tiny biting
insects; the larger holes in the Trap MK01's cup or bag (both are
included) may let some slip through. The Applica SonicWeb ICH500,
$300, has a small loudspeaker that generates the sound of a heartbeat.
A plastic frame surrounding the speaker includes an electric heating
element, a hook for hanging an octenol lure, and a cylinder that holds
a sticky paper sleeve that captures mosquitoes only if they land on
it.

How we tested. We released a couple thousand mosquitoes into a
25-by-30-foot sealed room with a trap at one end. About half were
Culex quinquefasciatus, a species that has helped spread West Nile
virus into the southern U.S. (Culex pipiens, a close relative with
almost identical habits, is mainly to blame for the outbreak in the
North.) The rest were Aedes aegypti, a common southern species that's
especially tenacious in its pursuit of people.

We ran each trap for 20 hours, half of that time in the dark, then
recorded the number and species of mosquitoes caught in each device.

How they performed. Within minutes of entering the test chamber,
swarms of mosquitoes clustered around the Magnet Liberty and Mosquito
Trap MK01. Some mosquitoes swarmed near the SonicWeb, but many perched
on its frame instead of landing on the sticky sleeve.

By the end of its 20 hours, the Magnet Liberty had caught about
three-fourths of the mosquitoes; so had the Trap MK01. The SonicWeb
had trapped only about one-fourth. The bug zapper killed far fewer,
even though it provided the only light in the room during our
simulated night. All three traps caught about twice as many Aedes
mosquitoes as Culex. That's probably because Aedes are highly
aggressive and like to bite the mammals that the machines impersonate.
Culex are less aggressive and prefer birds.

In general, the more traps in a neighborhood and the more strategic
their placement (between a swamp and a backyard, say), the more
effective the control.

How easy they are to use. To avoid luring mosquitoes to people, you're
supposed to put traps far from areas where people gather. You may need
several long extension cords, which can be inconvenient. The Magnet
Liberty and Trap MK01 must be placed so the prevailing breeze carries
the gas plume across the yard. Because of their use of electricity,
propane, or chemicals, all the traps must be used only outdoors and
should be placed where children are unlikely to touch them.

The Magnet Liberty and Trap MK01 look like robot brothers, but the
shorter Magnet Liberty is easier to use. It nestles inside a compact,
stable metal frame that can be wheeled with little effort. It has
electronic controls and ignition, and its fan is barely audible from a
few feet away. The Trap MK01 is top-heavy and has no wheels, so it's
hard to move. You ignite it with a match or lighter, and its fan is as
loud as an air conditioner, though that shouldn't be distracting when
the device is placed as recommended.

The SonicWeb is a cinch to set up: Hang the octenol lure, pop on the
sticky paper sleeve, and plug it in. Its thumping "heartbeat" is
quieter than the Trap MK01's fan. But again, in our tests, the
SonicWeb was much less effective than the others.

Recommendations. Our tests were conducted in a lab, not outdoors.
Still, they indicate that if traps are continuously operated under the
right circumstances, they can reduce the number of mosquitoes in your
yard. Our top choice, the Mosquito Magnet Liberty, $500, performed
well and was easy to use.

Traps are expensive. After paying hundreds of dollars for the device
itself, you'll pay $20 to $25 a month for electricity and components
such as propane, octenol lures, and sticky paper. And traps are
unlikely to prevent all bites. Therefore, consider low-tech approaches
first: Apply repellent, wear protective clothing, and eliminate
mosquito-breeding habitats in and near your yard.