Mosquito Traps: What To Look For

Mosquito traps use attractants to lure insects

Most mosquito traps require round-the-clock operation and an electrical outlet, which compromises portability. The carbon dioxide (CO2) used as an attractant in many mosquito traps mimics human exhalation; it is typically produced using standard 20-pound propane tanks that must be replaced every three weeks, on average, and are rarely included in the price of the trap. (Some traps use propane to provide both power and a source of CO2.) Other chemical attractants, including octenol and Lurex (a lactic acid-based substance) or a combination of the two, are provided via a cartridge or strip that must be replaced regularly. When mosquitoes approach a trap, they are captured by a vacuum or sticky strip.

Overall, experts recommend using a combination of carbon dioxide and octenol as a primary attractant for mosquitoes. For years, entomologists have used CO2 as bait, and the vast majority of commercial traps still do. One study published by the American Mosquito Control Association found that adding octenol to CO2 increased the number of mosquitoes captured fivefold and led to a greater number of species captured.

It's important to remember, however, that different species respond to different attractants. The Asian tiger mosquitoes that are more common in the southern United States, for example, are particularly attracted to the scent of Lurex. "Before you buy a trap, it's crucial that you know what mosquito species is causing your problem," says Jonathan Day, a University of Florida entomologist, in a university release on mosquito traps. To get help, consumers can contact county extension agents or trap manufacturers.

If you're considering a mosquito trap purchase, keep the following points in mind:

• Experts are skeptical of manufacturers who claim that their traps can protect an acre or more of land. One trap may not do the trick for a large area that is heavily infested. Daniel Kline, one of the most respected authorities on mosquito control, says, "Any claim about coverage isn't scientifically based. There are so many factors involved."

• Placement of mosquito traps is important. Try to place traps that catch all angles of the wind. The prevailing breeze should carry the gas plume across the yard, since mosquitoes follow CO2. Wind speed and direction may change, and some owners, like Kline, report using several traps and placing them in different corners of the area they want to cover.

• Read and follow the owner's manual to prevent maintenance problems later on.

• Don't rely exclusively on traps for mosquito control. Apply repellent and wear protective clothing. (ConsumerSearch has a separate report on insect repellent, which includes personal sprays and lotions.) In addition, eliminate standing water in your yard where mosquitoes may breed.

• For a less invasive approach, try larvicides. Larvicides, such as Mosquito Dunks from Summit Chemical Company (*Est. $20 for a card of 20), can be dissolved into any body of water in your yard, such as an ornamental fish pond or bird bath. They contain bacteria that kill mosquito eggs before they hatch, but are not harmful to humans, fish or other animals.

• Another option is to introduce predators that feed on mosquitoes. Bats and dragonflies can accomplish this. Dragonfly nymphs can be purchased from companies that specialize in selling insects and animals to schools. According to Bat Conservation International, a single bat can capture 500 to 1,000 mosquitoes in a single hour. However, experts note that bats eat many kinds of insects, not just mosquitoes.

• Mosquito traps usually aren't for indoor use. Mosquito traps use electricity, propane or chemicals. Only use them outdoors and out of reach of children. An exception is the Stinger MA06 Indoor Mosquito Trap (*Est. $25), which is for indoor use only. It gets average ratings overall from over 60 Amazon.com users. It attracts and kills all flying insects, not just mosquitoes and other biting insects.

Although Mosquito Magnet and other traps produce CO2 -- which is known to contribute to global warming -- most reviews say that the amount of CO2 produced isn't enough to have a serious environmental impact, especially in areas where the alternative would be spraying pesticides. Users posting comments at Treehugger.com and WorldChanging.com say preventing the spread of West Nile Virus and malaria probably balances the small amount of CO2 production. If you're particularly concerned over the potential environmental impact of running a mosquito trap, you could also help minimize the effect of the emissions by planting additional trees and plants in your yard (plants absorb CO2).

Many other types of devices claim to control mosquitoes, but experts say they just don't work as well as mosquito traps. Electronic devices that claim to repel mosquitoes by emitting high frequency sounds are considered ineffective by reviewers, as are Citrosa plants. Studies have also shown that electrocuting bug zappers kill mostly beneficial insects, such as beetles and moths, rather than mosquitoes. In one test, bug zappers didn't kill more mosquitoes than were trapped on sticky paper. Similarly, bug foggers are less discriminating than traps, may contain dangerous chemicals and do not kill mosquito eggs.