Carbon dioxide mosquito traps no magic bullet, say UF experts

May 19, 2005

VERO BEACH, Fla. — With spring rains promising a bumper crop of mosquitoes, some Floridians may consider buying expensive high-tech traps that use carbon dioxide to lure the bloodsuckers. But University of Florida experts warn that buyers who don’t do their homework could still get bitten – in the pocketbook.

Priced from $300 to $1,500, the traps do capture mosquitoes and other biting insects, said Jonathan Day, an entomologist with UF’s Institute of Food and Agricultural Sciences. The real question is whether they will protect a yard from the pests, he said.

The state is home to 74 species of mosquitoes, of which about half prey on people, he said. Only a few species are likely to be controlled with a CO2 trap because variables such as flight range, habitat preference and feeding behavior determine whether the trap will capture mosquitoes in large enough numbers to reduce biting around the home.

“Before you buy a trap, it’s crucial that you know what mosquito species is causing your problem,” Day said. “The traps can be very effective if the target insect is one that doesn’t fly very far or has its breeding site near your home. But most of the mosquitoes people complain about in Florida have flown a considerable distance before they end up in someone’s back yard and using a trap to control them is like trying to capture all the grains of sand on the beach.”

Consumers can get help identifying mosquitoes by contacting UF/IFAS county extension agents, he said. To assess whether a CO2 trap could help, an agent will need to know about vegetation and surface water in and around the property.

The traps lure mosquitoes by emitting carbon dioxide, a gas people and animals produce when they breathe, Day said. Some traps use additional chemicals to mimic other scents. When mosquitoes reach the trap they are captured by a vacuum or adhesive.

Day, who has used CO2 traps as a research tool for 10 years at the Florida Medical Entomology Laboratory in Vero Beach, said despite the traps’ efforts to fool mosquitoes with CO2 and other attractants, the insects prefer people and animals. He is concluding a study that showed CO2 traps were significantly outperformed by traps that used live hosts as bait.

Because CO2 traps have only been available to consumers since the late 1990s, manufacturers are still refining the technology, said Joe Conlon, a staff entomologist and spokesman with the American Mosquito Control Association, a nonprofit organization in New Jersey.

“The attractants don’t seem to be working as well as theoretically possible, and we need a whole lot more research into the physiology of attractiveness of humans to mosquitoes,” Conlon said.

Species-specific attractants could help consumers solve pest problems more reliably, said Raymond Iannetta, chairman and chief executive officer of American Biophysics Corporation, the first company to produce a CO2 mosquito trap for the consumer market, the Mosquito Magnet trap. The Rhode Island company is also the first to develop attractants based on human skin scents, and recently introduced an attractant designed for the Asian tiger mosquito, he said.

Iannetta said consumers and scientists may view CO2 traps with skepticism because other mosquito control devices such as electric “bug zappers” are not based on valid science. He asserts that his company’s products are effective, and are based on 14 years of rigorous scientific research and testing.

“A significant hurdle was getting over the industry’s gadget or gimmick syndrome,” he said. “We’re constantly working with the scientific community and the public to change that perception.”

The company maintains an extensive Web site to educate consumers about the traps, how they work and how consumers can best use them, Iannetta said.

Experts agree that operator error can impair a CO2 trap’s performance, said Dan Kline, a research entomologist with the U.S. Department of Agriculture’s Center for Medical, Agricultural and Veterinary Entomology in Gainesville.

“It’s important that people read and follow the owner’s manual,” said Kline, who regularly tests CO2 traps for manufacturers and is conducting a study to determine if multiple CO2 traps can protect a neighborhood. “Placement is a big issue – you need to keep the trap out of the immediate area where people gather, and try to put it between the people and the source of the mosquitoes.”

Another common problem is that consumers sometimes use the traps only during outdoor activities, rather than running them continuously during warm weather, as manufacturers recommend, he said. ‘Round the clock operation of one trap can cost $20 to $25 per month.

No one should rely exclusively on a CO2 trap for mosquito control, said Roxanne Rutledge, an entomologist at the UF laboratory in Vero Beach. Consumers should also follow traditional precautions such as using repellent, eliminating sources of standing water and patching holes in screens.

“Try to keep a balance,” she said. “Do things around your home to reduce the number of mosquitoes that breed or get inside, but understand there are factors beyond your control.”

Ultimately, a consumer’s tolerance for mosquito bites may be the only way to measure success with a CO2 trap, Rutledge said.

“It comes down to a matter of perception,” she said. “You can have one of these in your yard, and if you feel like you’re not being bitten by mosquitoes anymore and you’re happy with it, then for you it works.”

For more information about CO2 mosquito traps, see Rutledge’s fact sheet “Mosquito Control Devices and Services for Florida Homeowners” at http://edis.ifas.ufl.edu/in171.