Mosquito Traps

How mosquito traps work

Since the first "light traps" were introduced in 1989, the number of traps has ballooned in response to demand from homeowners who want protection from mosquito-borne diseases such as West Nile Virus. But experts warn that these pricey mosquito traps -- while more effective than bug zappers and foggers -- are not a cure-all. "My gut feeling is that most times one trap is really going to reduce the population to the level that you need to," says Daniel Kline, a research scientist for the U.S. Department of Agriculture who has studied mosquito traps for nearly 20 years. But he added a word of caution: "I don't care what the mosquito control method is, you're going to get bitten."

Most traps require round-the-clock operation and an electrical outlet, which compromises portability. The most effective traps attract mosquitoes with a combination of carbon dioxide (some traps use propane to provide both power and a source of CO2) and octenol (another chemical attractant). The standard 20-pound propane tank must be replaced every month, on average, and is rarely included in the price. The plume of CO2 imitates human exhalation, making the traps effective for capturing blood-feeding insects while leaving beneficial insects alone. When mosquitoes approach the trap, they are captured by a vacuum or sticky strip, where they desiccate and die. Since mosquitoes still prefer people and animals to impostors, some traps include a separate fan device designed to mask human odor.

Many products purport to significantly reduce or even decimate the local mosquito population, but even the American Mosquito Control Association is skeptical of such claims. An article about mosquito traps on the association's Web site warns consumers that "acre-wide control by these devices may be somewhat overstated," noting that many studies are conducted in controlled screened-in areas. The article further states that the association has received a number of complaints from dissatisfied buyers. Association officials are unclear whether the complaints should be attributed to a design flaw or to buyers not following placement and maintenance instructions. In an interview, the Association's technical advisor, Joe Conlon, says, "There's a million things that can go wrong." He recommends that traps be used in well-defined breeding habitats, such as swamps or near standing water. Most people can get by slathering on repellents rather than investing in a trap, adds Conlon.

Factors that can influence how many mosquitoes get trapped include the mosquito population size, the trap's proximity to the breeding habitat, feeding behavior, wind speed, and what species are present. In the end, reviews recommend combining mosquito traps with other low-tech means of mosquito control, such as larvicides and insect repellents. Like any attractant, you may end up attracting more mozzies than you would have without the trap.

Best mosquito traps

An overwhelming amount of testing has focused exclusively on the Mosquito Magnet line of mosquito traps, probably because it's considered an industry leader based on its "counterflow technology." Mosquito Magnet traps consistently outperform the competition, both in the number of mosquitoes captured and the diversity of species represented. In one Florida research study, a set of Mosquito Magnet traps caught more than 91,000 mosquitoes in 18 species and more than 2 million sand flies in one month, along with significantly reducing the landing rates in a subdivision. Other comparative studies found that Mosquito Magnet traps captured two to three times more mosquitoes than their closest competitor.

The three Mosquito Magnet traps in the series use the same basic technology, generating CO2 and heat by burning propane, and they come with a cartridge of octenol (believed to smell like cow's breath to a mosquito). A vacuum sucks mosquitoes and other tiny biting insects into a fine-mesh net, where they dehydrate and die. It is recommended that the net be emptied every two to three weeks.

The Mosquito Magnet Defender (*est. $300) is the smallest trap, made for about .5 acre. The Liberty (*est. $450) is made for about an acre. (Keep in mind that many reviews say there's little chance these acreage estimates could be accurate, since there are so many variables.) Both the Defender and Liberty have a 50-foot power cord. The propane and octenol must be replaced about every three weeks. The Mosquito Magnet Liberty Plus (*est. $630) has a larger collection bag and uses a NiMH battery pack instead of a power cord. The Mosquito Magnet Pro (*est. $1,250) is also cordless, and made to cover a 1.5-acre area, with a large collection bag. The Pro also is fitted with a small solar panel to act as a backup power source.

We selected the Mosquito Magnet Liberty for Fast Answers because it earns more review recommendations than the other Magnet models and costs substantially less than the cordless Mosquito Magnet Pro. If you want to be free of a cord, the Liberty Plus is an option, though it's quite a bit more expensive.

Several reviews praised the Liberty for ease of use, though it may require several extension cords. Daniel Kline, a USDA researcher who lives adjacent to Florida wetlands, said he keeps four cordless Magnet Liberty Plus models in his 3/4-acre backyard with good results. For heavily infested areas, the Pro may be a better option, but it costs more than double the Liberty. Like the Liberty Plus, the Pro is self-contained, but it also comes with an extra-large net and claims to cover a wider area. One USDA test found that the Pro captured as much as twice the number of mosquitoes than the Liberty overnight.

Reviews question the Magnet line's effect on other biting insects. A Florida A&M University study found no significant reduction of biting midges from yards with Mosquito Magnet compared to control yards. The Maryland Department of Agriculture evaluated the Mosquito Magnet in 2001 and determined that it was helpful in collecting mosquitoes for surveillance, but that the manufacturer's claims of controlling the population could not be corroborated.

Dozens of contributors to Epinions and Amazon say the Magnet Liberty is effective -- when it's working. Reviewers complain that it is expensive to maintain and vulnerable to breakdowns. American Biophysics, the company that manufactures the Magnet, recently changed suppliers to improve quality control, Conlon said. Even so, no Mosquito Magnet model receives more than three aggregate stars (out of five) at Amazon.com, and many owners are angry that their Mosquito Magnet only lasted one season.

The Mega-Catch line of mosquito traps provide an alternative for those who don't feel comfortable using propane (or for those who want to avoid the ongoing expense of propane tanks) The Mega-Catch mosquito trap doesn't produce CO2. Instead, it relies on a combination of octenol with an LED light system and a UV light attractant to lure biting insects. The most expensive Mega-Catch Ultra (*est. $470) includes an optional CO2 gas system (the CO2 must be purchased separately) that claims to release a purer form of CO2 than propane by using the same cylinders as the beverage industry. The CO2 is released at varying rates over fixed intervals. We found a couple reviews touting the Mega-Catch mosquito trap's overall efficiency and ability to adapt to different species. The Mega-Catch Premier (*est. $250) competes directly with Mosquito Magnet's Defender, the line's lowest-priced model.

The Mega-Catch Premier mosquito trap, which claims to protect an acre at most, incorporates a programmable timer that can be adjusted to operate only when a particular species is active. It includes a 110/12 volt weatherproof transformer, a liquid catch and standard catch bag, an optional octenol fragrance strip, and a 60-foot-long extension cord. The less expensive Mega-Catch Alpha mosquito trap (*est. $150) can be mounted on a table and claims to protect half an acre. It contains only a catch bag. However, we found no objective testing for this model. We did see in some tests, but only on the manufacturer's Web site, and we were unable to verify those tests as independent. The most expensive Mega-Catch Ultra (*est. $470) includes an optional C02 gas release system and claims to protect 1 1/2 acres. Reviews say Mega-Catch is good because it is relatively lightweight and effective, but Mosquito Magnet still has the edge in reviews.

We found no totally objective studies comparing Mega-Catch with Mosquito Magnet. One older study from 2001 does compare older Mosquito Magnet models with Mega-Catch mosquito traps. The results are interesting in that Mega-Catch appeared better at capturing certain types of species, while Mosquito Magnet was better at trapping other species. Both were effective overall, but in different ways. However, this test is published only on the Mega-Catch Web site, and we were unable to verify whether the manufacturer sponsored the testing. The wider praise for the Mosquito Magnet traps is hard to ignore, though Mega-Catch traps are an alternative for those that don’t want to use a propane tank. We hope to see more objective comparison tests conducted in the future.

Overall, experts recommend using a combination of CO2 and octenol as a primary attractant for mosquitoes. For years, entomologists have used CO2 as bait; the vast majority of commercial traps still do. It's no surprise then that manufacturers are pouring money into finding the best attractant. 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. While some mosquitoes may be attracted to human blood, others like the blood of wild or domestic animals. In the Salt Lake City study, for instance, an earlier version of the Mosquito Magnet Liberty captured 198 Ae. sierrensis mosquitoes per night and zero Cx. Pipiens mosquitoes. By contrast, the Mosquito Magnet Pro trapped 13 Ae. sierrensis and 34 Cx. pipiens. A study that appeared in the Journal of Chemical Ecology found that four Ae. aegypti populations of mosquitoes from different geographic regions all responded to lactic acid, a key attractant compound from human skin, but the required dose varied. Also, attraction increased significantly for some species when lactic acid was combined with both ammonia and caproic acid.

The Mosquito Magnet mosquito trap can accommodate lurex as a replacement attractant for the Asian Tiger mosquitoes that are more common in the south. "Before you buy a trap, it's crucial that you know what mosquito species is causing your problem," Jonathan Day, a University of Florida entomologist said in a university release on mosquito traps. To get help, consumers can contact county extension agents or trap manufacturers. Mega-Catch traps don't have a lurex option.

Important Features: Mosquito traps

Reviewers say the following about mosquito traps:

• 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, of the most respected authorities on mosquito control, uses four mosquito traps for his .75-acre yard.

• Placement of mosquito traps is important. Try to place traps between the people and the source of the mosquitoes. The prevailing breeze should carry the gas plume across the yard.

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

• Traps must run continuously during warm weather. Round-the-clock operation can cost an estimated $20 per month, plus propane and replacement octenol.

• Don't rely exclusively on traps for mosquito control. Apply repellent, eliminate standing water in the yard, and wear protective clothing.

• 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.

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 DDT. Commentators at Treehugger.com and WorldChanging.com say that preventing the spread of West Nile Virus and malaria probably balances the small amount of CO2 production. You could also help minimize the effect of emissions by planting additional trees and plants in your yard (plants absorb CO2).

Our Consensus Report shows how many times products are top-ranked by reviewers included in our
All The Reviews Reviewed chart.

# of Picks	Model (with retailer links)	Details from Amazon.com
3	Mosquito Magnet Liberty (*est. $450)	details
2	Mega-Catch Premier (*est. $250)	-
2	Mosquito Magnet Pro (*est. $1,250)	details
1	Lentek MK12 Mosquito Trap Guardian (*est. $310)	details

The Magnet Liberty consistently outperforms its closest competitors by trapping more mozzies and a greater variety of species. It's a less expensive alternative to the cordless Magnet Pro , which is recommended for heavily infested areas. The Mega-Catch will appeal to those who don't want a cumbersome propane tank. The Lentek model generally receives low ratings for effectiveness and portability when compared to the Magnet line of mosquito traps.

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