Do those mosquito zapper things really work?

Ideally, you’d like to go outside and fire up the grill, or weed in the garden, without having a hoard of ferocious mosquitoes circling your head. Unfortunately, it usually doesn’t work out that way.

There’s a huge amount of devices on the market that claim to kill mosquitoes, or drive them out of your yard. So far, all but one kind of these has turned out to be bogus.

Ultrasonic Repellers Are Worthless

Electronic devices that claim to repel mosquitoes by emitting high frequency or ultra sounds are ineffective. Period.

They also appear to have some negative effects on pets, who can hear ultrasound or high frequency ranges.

A review of 16 peer-reviewed papers in 2000 found that not a single one of the ultrasonic devices tested had an effect. An additional review in 2007 also found that newer ultrasonic repelling devices were…newer. And completely useless at repelling mosquitoes.

Unfortunately, the number of fraud convictions for those peddling these devices has been small, mainly because there isn’t much public outcry.

Zappers kill the wrong bugs

Electrocuting bug zappers that use ultraviolet light to attract insects kill beneficial insects, such as beetles and moths, not mosquitoes. Mosquitoes are not strongly attracted to UV light, but many pollinating insects are.  A key study from some time ago lays it out pretty starkly:

Frick, T. B. and D. W. Tallamy. 1996. Density and diversity of nontarget insects killed by suburban electric insect traps. Ent. News 107(2): 77-82:

“Of the 13,789 insects counted, only 31 were biting flies. Nearly half of the insects collected were nonbiting aquatic insects such as caddisflies and midges. More importantly, 1,868 predators and parasites (13.5%) were destroyed within 27 families of predators and nine families of parasitoids.”

That’s 0.2% of the total insects fried that were actual biting species of flies.  The rest were insects important in ecosystem functioning and pollination.  Please. Do. Not. Use. These. Devices.

Some more recent work suggests that these devices, when used indoors, can be a significant source of food contamination as fried bug parts and bacteria fly out of the zapper.

What devices do work to drive away mosquitoes?

Mosquitoes find you mainly by following your breath–specifically, CO2 (carbon dioxide)–and your body heat. So, the more you flap your arms and wave the mosquitoes away, the more of them will find you. Curses!

The only devices that have been consistently been shown to work over a large area are one of several brand name mosquito traps–the best known is the Mosquito Magnet. Like its name suggests, the trap actually doesn’t drive the mosquitoes away, but lures them into their death.

These traps attract mosquitoes with a combination of carbon dioxide (some traps use propane) and octenol (another chemical attractant). The combination of heat and exhaled gasses makes the trap seem like a big juicy mammal to the mosquitoes.

Sounds great! But–it’s not as easy as buy one and plug it in. You have to carefully consider where you put it. If you stand downwind of the mosquito attractor, you are between it and the mosquito. They are likely to stop on you for a snack. From the American Mosquito Control Association:

“Please be cautioned against putting too much faith in traps as your sole means of control. These traps represent an evolving technology that is a most welcome addition to our mosquito control armamentarium. Their potential is great, but shouldn’t be overestimated. It is unclear whether the traps attract mosquitoes into an area where humans may then provide a stronger source of attraction.”

And for bonus points, use “armamentarium” in another sentence. :)

Unfortunately, the cheapest of these devices I’ve seen is about $300. While they do perform well in tests, the kinds of mosquitoes they capture varies widely. In an area where there is mosquito-borne disease, this could be a problem if you’re catching the wrong species of mosquitoes.

These are new devices, and as research continues, hopefully new information will be forth coming.

Lastly, some of the claims for these devices can be a little over the top. Multi-acre control is just not going to happen. Protecting your backyard, though, is quite possible.

Edited 10.2009 to add updated link to 2007 paper : Enayati A, Hemingway J, Garner P. Electronic mosquito repellents for preventing mosquito bites and malaria infection. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: CD005434. DOI: 10.1002/14651858.CD005434.pub2

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