How to Kill Mosquitoes: What Works and What Doesn't

Separating Mosquito Control Fact From Fiction

Most people believe the only good mosquito is a dead mosquito.
Most people believe the only good mosquito is a dead mosquito. doug4537 / Getty Images

Mosquitoes bite, suck your blood, and leave you with itchy bumps and possibly a horrible infection. Mosquito-borne pathogens include malaria, West Nile virus, Zika virus, Chikungunya virus, and dengue.

While you might fantasize about living in a mosquito-free world, eradicating them would actually be disastrous for the environment. Adult mosquitoes are food for other insects, birds, and bats, while larval mosquitoes support aquatic ecosystems. The best we can hope for is to limit their ability to transmit disease, repel them, and kill them within the confines of our yards and homes.

Mosquito-killing products bring in the big bucks, so it should come as no surprise that there is a wealth of misinformation out there. Before you get sucked into buying a product that simply won't work, get educated about what does and does not kill these blood-sucking pests.

How Not to Kill Mosquitoes

It's the smoke from citronella candles that repels mosquitoes, not the compound. The carbon dioxide from combustion actually attracts them.
It's the smoke from citronella candles that repels mosquitoes, not the compound. The carbon dioxide from combustion actually attracts them. Blanchi Costela / Getty Images

First, you need to understand the difference between repelling mosquitoes and killing them. Repellents make a location (like your yard or skin) less attractive to mosquitoes, but don't kill them. So, citronella, DEET, smoke, lemon eucalyptus, lavender, and tea tree oil might keep the insects at bay, but won't control or get rid of them in the long run.

There are a host of methods that actually do kill mosquitoes, but aren't great solutions. A classic example is a bug zapper, which kills only a few mosquitoes, yet attracts and kills beneficial insects that keep the mozzy population down. Similarly, spraying pesticides is not an ideal solution because mosquitoes can become resistant to them, other animals get poisoned, and the toxins can cause lasting environmental damage.

Source Reduction

You'll get fewer mosquitoes if they can't find standing water for breeding.
You'll get fewer mosquitoes if they can't find standing water for breeding. Esther Kok / EyeEm / Getty Images

Many species of mosquitoes required standing water to breed, so one of the most effective methods of controlling them is to remove open containers and repair leaks. Dumping containers of standing water kills the larvae living in them before they get a chance to mature.

However, removing water may be undesirable or impractical in some cases. Further, some species don't even need standing water to reproduce! The Aedes species, responsible for transmitting Zika and dengue, lays eggs out of water. These eggs remain viable for months, ready to hatch when sufficient water becomes available.

Biological Methods

Bacillus thurigiensis infects larval mosquitoes and damages their digestive system so they can't eat. It is not effective against adults.
Bacillus thurigiensis infects larval mosquitoes and damages their digestive system so they can't eat. It is not effective against adults. PASIEKA / Getty Images

A better solution is to introduce predators that eat immature or adult mosquitoes or infectious agents that harm mosquitoes without affecting other wildlife.

Most ornamental fish consume mosquito larvae, including koi and minnows. Lizards, geckos, dragonfly adults and naiads, frogs, bats, spiders, and crustaceans all eat mosquitoes.

Adult mosquitoes are susceptible to infection by the fungi Metarhizium anisoplilae and Beauveria bassiana. A more practical infectious agent is the spores of the soil bacterium Bacillus thurigiensis israelensis (BTI),. Infection with BTI makes the larvae unable to eat, causing them to die. BTI pellets are readily available at home and gardening stores, easy to use (simply add them to standing water), and only affect mosquitoes, black flies, and fungus gnats. The treated water remains safe for pets and wild animals to drink. The disadvantages of BTI are that it requires reapplication every week or two and it doesn't kill adult mosquitos.

Chemical and Physical Methods

Mosquitoes may be lured into traps using carbon dioxide, heat, humidity, or hormones.
Mosquitoes may be lured into traps using carbon dioxide, heat, humidity, or hormones. Alaguir / Getty Images

There are several chemical methods that target mosquitoes without the risks to other animals that come with spraying pesticides.

Some methods rely on chemical attractants to lure mosquitoes to their doom. Mosquitoes are attracted to carbon dioxide, sugary scents, heat, lactic acid, and octenal. Gravid females (those carrying eggs) may be attracted to traps laced with a hormone released during the egg-laying process.

The lethal ovitrap is dark, water-filled container, typically with a small opening to prevent larger animals from drinking the water. Some traps use chemicals to bait the traps, while others simply provide a convenient breeding ground. The traps may be filled with predators (e.g., fish) or with dilute pesticide to kill larvae (larvicide) and sometimes adults. These traps are highly effective and affordable. The disadvantage is that multiple traps must be used to cover an area (about one every 25 feet).

Another chemical method is the use of an insect growth regulator (IGR), added to water to inhibit larval development. The most common IGR is methoprene, which is supplied as a time-release brick. While effective, methoprene has been shown to be mildly toxic to other animals. 

Adding a layer of oil or kerosene to water kills mosquito larvae and also prevents females from depositing eggs. The layer alters the surface tension of the water. Larvae can't get their breathing tube to the surface for air, so they suffocate. However, this method kills other animals in the water and makes the water unfit for consumption.

Physical Methods

Mosquitoes can be sucked into a fan to be caught on a screen or other trap.
Mosquitoes can be sucked into a fan to be caught on a screen or other trap. David Baker - S9Design / Getty Images

One example of a physical method of killing mosquitoes is swatting them with your hand, a fly-swatter, or an electric swatter. Swatting works if you've only got a few mosquitoes, but it's not particularly helpful if you're being swarmed. While bug zappers aren't ideal outdoors because they can unnecessarily kill beneficial insects, electrocuting indoor insects isn't generally considered objectionable. Just remember, you need to bait a bug zapper to attract mosquitoes, because they don't care about the pretty blue light.

Because mosquitoes are not strong fliers, it's also easy to suck them onto a screen or into a separate trap using a fan. Mosquitoes caught using a fan die from dehydration. Screen-traps may be made at home by fastening window screening fabric over the back of a fan.

The Bottom Line

You may need to use a combination of methods to kill mosquitoes.
You may need to use a combination of methods to kill mosquitoes. stefano petreni / EyeEm / Getty Images

If you're serious about killing mosquitoes, you'll probably need to use a combination of methods to control them. Some of the most effective strategies target either the larvae or the adult. Others kill mosquitoes at all stages of their life cycle, but may miss some of the insects.

If you live in a wetland area and get a significant influx of mosquitoes from outside your property, you won't be able to kill all of the local population. Don't despair! Scientists are developing ways to make mosquitoes sterile or lay eggs that won't mature. In the meanwhile, you'll need to combine repellents with lethal measures to enjoy the outdoors.

Fast Facts

  • The best way to kill and control mosquitoes is to consistently apply more than one method. Some methods may only target adults, while others may only target larvae.
  • Effective ways to kill mosquitoes include removing breeding grounds, encouraging predators, applying an agent containing BTI or IGR, and using traps.
  • Insect repellents and bug zappers don't kill mosquitoes.
  • Pesticide-resistant mosquitoes may survive spraying, plus the chemical kills other animals and may persist in the environment.

References

  • Canyon, D.V.; Hii, J.L. (1997). "The gecko: An environmentally friendly biological agent for mosquito control". Medical and veterinary entomology11 (4): 319–323.
  • J. A. A. Le Prince. (1915). "Control of Malaria: Oiling as an Antimosquito Measure". Public Health Reports30 (9).
  • Jianguo, Wang; Dashu, Ni (1995). "31. A Comparative Study of the Ability of Fish to Catch Mosquito Larva". In MacKay, Kenneth T. Rice-fish culture in China. International Development Research Centre. (archived)
  • Okumu FO, Killeen GF, Ogoma S, Biswaro L, Smallegange RC, Mbeyela E, Titus E, Munk C, Ngonyani H, Takken W, Mshinda H, Mukabana WR, Moore SJ (2010). Rénia L, ed. "Development and Field Evaluation of a Synthetic Mosquito Lure That is More Attractive than Humans". PLoS ONE. 5 (1): e8951.
  • Perich, M. J., A. Kardec, I. A. Braga, I. F. Portal, R. Burge, B. C. Zeichner, W. A. Brogdon, and R. A. Wirtz. 2003. Field evaluation of a lethal ovitrap against dengue vectors in Brazil. Medical and Veterinary Entomology 17: 205-210.
  • Zeichner, B. C.; Debboun, M (2011). "The lethal ovitrap: A response to the resurgence of dengue and chikungunya". U.S. Army Medical Department Journal: 4–11.