Mosquito bites aren't just an annoyance; they can be deadly. Mosquitoes transmit serious diseases, from malaria to West Nile virus. If you're planning to spend any time outdoors, you should protect yourself from mosquito bites. Many people hang insect electrocution lights, or bug zappers, in their backyards to kill biting insects. Unfortunately, research shows that most bug zappers do little to eliminate mosquitoes. Worse, they are more likely to eliminate beneficial insects that provide food for birds, bats, and fish.
How Bug Zappers Work
Bug zappers attract insects using ultraviolet light. The light fixture is surrounded by a mesh cage, which is energized with a low-voltage current. Insects are drawn to the UV light, attempt to pass through the electrified mesh, and are subsequently electrocuted. Most bug zappers are designed with a collection tray where the dead insects accumulate. From dusk until dawn, homeowners with bug zappers hear the satisfying crackle of insects meeting their maker.
How Mosquitoes Find Blood
When evaluating mosquito control products, it's important to understand how mosquitoes locate a source of blood. In other words, think about how the mosquito finds someone to bite. Regardless of whether they're human, canine, equine, or avian, all living blood sources emit carbon dioxide. Mosquitoes, like most biting insects, can home in on the scent of carbon dioxide in the air. Research suggests a bloodthirsty mosquito can detect carbon dioxide from as far as 35 meters away from its source.
At the slightest hint of CO2, the mosquito begins flying in zigzags, using trial and error to pinpoint the person or animal in the area. Carbon dioxide is the most powerful attractant for mosquitoes. Mosquitoes also use other scent clues to find people to bite. Perfume, sweat, and even body odor can attract mosquitoes.
Research Proves Bug Zappers Are Ineffective for Killing Mosquitoes
Bug zappers attract insects using ultraviolet light. Mosquitoes find their blood meals by following the trail of carbon dioxide. Occasionally, a mosquito will get curious about the pretty light and make the fatal mistake of getting too close. But there's no guarantee that mosquito is even a female, and therefore a biting mosquito. In fact, many of the "mosquitoes" found in bug zappers are actually nonbiting insects called midges.
In 1977, researchers from the University of Guelph conducted a study to determine how effective bug zapper products are at killing mosquitoes and reducing mosquito populations where they are used. They found that just 4.1% of the insects killed in the bug zappers were female (and therefore biting) mosquitoes. The study also found the yards with bug zappers had higher numbers of female mosquitoes than those without bug zappers.
University of Notre Dame researchers conducted a similar study in 1982, with similar results. In an average night, a single bug zapper in South Bend, Indiana, killed 3,212 insects, but only 3.3% of the dead insects were female mosquitoes. In addition, these researchers found that the UV light seemed to draw more mosquitoes to the area, leading to more mosquito bites.
In 1996, researchers at the University of Delaware tallied an entire summer's worth of dead bugs from bug zappers. Of a total of 13,789 insects killed in the bug zappers, a paltry 0.22% of them were biting mosquitoes or gnats. Worse, almost half of the dead insects were harmless, aquatic insects, an important food for fish and other stream inhabitants. These insects help control pest insect populations, meaning bug zappers could actually make pest problems worse.
Scientists at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach, Florida, also examined the effectiveness of bug zappers in 1997. A single bug zapper in their study killed 10,000 insects in one night, but just eight of the dead bugs were mosquitoes.
New Octenol Bug Zappers
In recent years, a new type of zapper has appeared on the market that uses carbon dioxide and octenol-a nontoxic, pesticide-free pheromone-to attract mosquitoes. Logically, this new type of zapper should attract and kill more mosquitoes, leaving your yard pest-free.
Unfortunately, studies show that octenol does little to increase the number of mosquitoes killed per night. Instead, it attracts even more mosquitoes to your yard, while killing about the same number of pests as a strip of sticky tape.
Study after study has proven that bug zappers do very little or nothing at all to put a dent in the biting mosquito population. On the other hand, limiting mosquito breeding habitat and using appropriate mosquito deterrents like DEET does protect you from mosquito bites, and from the diseases mosquitoes carry.
- Surgeoner, G. A., and B. V. Helson. 1977. A field evaluation of electrocutors for mosquito control in southern Ontario. Proc. Entomol. Soc. Ontario 108:53-58.
- Nasci, RS, CW. Harris and CK Porter. 1983. Failure of an insect electrocuting device to reduce mosquito biting. Mosquito News. 43:180-184.
- Frick, TB and DW Tallamy. 1996. Density and diversity of nontarget insects killed by suburban electric insect traps. Ent. News. 107:77-82.
- University Of Florida, Institute Of Food & Agricultural Sciences, 1997. "Snap! Crackle! Pop! Electric Bug Zappers Are Useless For Controlling Mosquitoes, Says UF/IFAS Pest Expert" Accessed September 4, 2012.