Below are some tips on reducing the number of mosquitoes in your yard.
Eliminate breeding sites
Mosquitoes can develop in as little as 1 teaspoon of water in as little as 5 days, so if you purge your yard of all objects that can accumulate water, female mosquitoes will be completely unable to lay eggs in your yard. They will then go elsewhere and their progeny will be somebody else’s problem. The gallery below illustrates some examples of objects to remove or alter (e.g., drill drainage holes) so they don’t accumulate water.
Other objects of concern are: pool covers, pot saucers, grill covers, plastic kid toys, tires, unattached hoses, empty glazed pots, shovels, construction dumpsters, construction materials, garbage cans, garbage can lids, containers in recycling bins, bottle caps, cemetery vases, bamboo garden stakes, decorative shells, empty coconuts, papaya tree stumps, downspout troughs, pickup truck beds, window wells, septic tanks, uncapped metal fence posts, uncapped water-filled traffic barriers.
Some mosquitoes lay their eggs on damp logs, twigs, and leaves in low areas in the yard, so clear out piles of debris that might become temporarily flooded during heavy rains. If you click on the image at right you can dozens of Asian tiger mosquito eggs on a wet log. Mosquito eggs can stay dormant for a year so this advice applies to areas that rarely accumulate water, too.
And some mosquito species can complete their life cycle inside your house so make sure that you don’t leave dishes in the sink for more than 5 days. They also can breed in toilet bowls that might be in bathrooms that don’t get used regularly. French drains also have been known to harbor mosquitoes (add screening to keep them out).
Form a Neighborhood Mosquito Watch
A few neglected containers in town can ruin everyone’s back yard, so be proactive when you see larvae (movie below): dump them out or give the owner a heads up (example). Get your friends and neighbors to do the same. And definitely train your kids to recognize larvae, too, because more than likely it is your kids’ toys that are filling up with stagnant water.
Kill larvae with Bti
If you have items that are supposed to hold water, add cakes (e.g., MosquitoDunks) or granules of Bacillus thuringiensis var israelensis (abbreviated, Bti), a bacterium that evolved to infect mosquito larvae. It’s extremely effective: you can add it a container that has thousands wriggling of larvae and they will all be dead within hours. And you can add Bti to uninfested water to protect it from mosquito larvae for weeks. Bti cakes/granules can be purchased from any hardware store on the planet, plus online and are completely safe for humans, birds, pets, honeybees, butterflies, etc. I.e., you can add it to your dog’s water bowl and your fish ponds. But you have to add these Bti products regularly to ensure effectiveness so mark reapplication times on your kitchen calendar or put nagging reminders into your smartphone. Here are some visual examples of places to seed with Bti:
Additional sites that need regular Bti treatment are: rain barrels, sub-irrigated planters, water features, water gardens, fish ponds, drainage ditches, and rooftop cisterns. And per the EPA, “Bti can be sprayed over waterbodies such as ponds, lakes, rivers and streams” so don’t worry about using it in those locations.
Use Bti indoors, too. If your French drains are not screened just add cakes regularly. And if you have a problem with mosquitoes breeding in your toilet bowls when you are off traveling, add Bti before you leave; or ask a house-sitter to flush everything.
Encourage mosquito predators
- Bats are often viewed as voracious consumers of mosquitoes but that view is largely due to one experiment that examined how many mosquitoes they’d eat if trapped in a room with nothing else. But they probably do eat some, so putting up a few bat boxes couldn’t hurt. Just don’t put the boxes over a place where your kids will play (rabies risk from poop).
- Dragonflies will eat mosquitoes, so maybe put a small pond in your yard to attract them. But it’s generally thought dragonflies’ ability to control mosquitoes is completely exaggerated. I agree.
- Swallows, purple martins, and barn swallows are also OK options. But, again, not great.
- I’d bet good money that the major, unsung predators of adult mosquitoes are jumping spiders (Salticidae). I don’t have any evidence to support this belief but I’d like to mention that there are two jumping spider species that have evolved to specialize on mosquitoes (Evarcha culicivora in Kenya, and Paracyrba wanlessi in Malaysia). So if you see jumping spiders in your yard, don’t kill them. They are also pretty cute.
Kill foraging females
Swatting works OK but there are several automated methods that can kill hundreds if not thousands per week.
- Buy chemical lure traps. These are fan-based devices that suck mosquitoes into a chamber where they’ll eventually die. The effectiveness varies with the specific chemical used in the lure so don’t despair if they don’t seem to work out of the box. Some lures will only attract certain species so check with somebody local to see which type might be best for your region. Once you figure out which kind works, buy a lot of traps and several packs of lures to get through the summer. If you’re handy, you can make them out of old CPU fans and solar panels (but you still need to buy the lures). If you’re way to cheap to buy lures you can experiment with old socks and smelly cheese (Limburger type).
- Buy a CO2 trap. These can be expensive ($1000 for some) but can be a great investment that can give you years of relief. You generally want to situate it in between you and the location you think mosquitoes are hiding. I.e., don’t situate it right where you hang out. I don’t own one but I’ve read that the number of mosquitoes in the “kill jar” is extraordinarily satisfying to see each time it needs emptying.
- One DYI technique that I love involves two box fans, some screening, and pyrethrum spray (buy at outdoor store or online). Cut a piece of screening (or tule fabric) to fit the surface of one of the fans and attach with tape, magnets, or screws. Coat the screening with permethrin and then situate the fans on either side of your favorite chair on a covered porch (so that fans OK when raining). Mosquitoes that zero in on your location will then be overcome by the wind and blown onto the pyrethrum-coated screening and will die. If I haven’t described it well enough to visualize, please see the diagram in “Protect your chickens” near the bottom of this page.
- If you have screen doors that you leave open for a breeze, spray the exteriors with permethrin. Then when mosquitoes land on screening they’ll pick up a lethal dose of pyrethroid and drop dead. You can also coat the perimeter of the door frame for good measure (mosquitoes like to wait around doors because they can smell the carbon dioxide leaking out around the door jam).
Make yeast-based traps that emit carbon dioxide and attract mosquitoes. No, don’t do that. Totally don’t work. Just a viral myth.
Trap and kill pregnant females
After females digest their blood meals they’ll search out stagnant water to lay eggs. Some species oviposit directly onto water in large rafts of eggs while others deposit eggs individually on objects right above the water line. This water-seeking behavior makes all species highly susceptible to trapping, especially if you’ve made the traps the only places in your yard with stagnant water. They simply won’t be able to resist. Traps are typically made of black plastic and have funnels, oil-coated surfaces, and sticky paper that prevent the mosquitoes from exiting the trap and laying eggs elsewhere. The eggs that are deposited are also killed — either with Bti in the water or by screening that traps pupae and adults below the water line. I prefer the latter method because it doesn’t require you to remember to keep adding Bti. You can make these traps rather cheaply if you’re handy (instructions) but you can also buy them (from Springstar or BioQuip, e.g.). For a typical yard you might want six. I especially like designs that allow you see the trapped adults and larvae because that helps convince neighbors and visitors that the gizmoes really work (and then they’ll want their own). But per multiple studies that deploy this traps in the real world, they do work like a charm, so even the ones that don’t have clear parts are worth the money.
Deploy larvicidal traps
A simpler option is to just leave out dark containers of water seeded with Bti cakes, some decaying leaves, and perhaps a rotting stick for good measure. Larvae that hatch in this water will die within hours. The trick with this strategy is that you have to remember to refresh the Bti cakes. If you forget (or go on a long vacation) the Bti might wear out and all your traps will become prime breeding ground for mosquitoes … and then you’ll feel like an idiot. That’s why screening is such a nice addition — eggs and small larvae drop through but the pupae and adults can’t get to the surface and will eventually die. If you have a spare tire and are handy, here’s a design that seems to be dramatically better than a simple container trap.
More trap ideas here, from scientist in Hawai’i: http://makemosquitotraps.org/.
Don’t let them bite you
- DEET works great. CDC also recommends picaridin (=icaridin), IR3535 (=ethyl butylacetylaminopropionate), and oil of lemon eucalyptus tree (p-menthane-3,8-diol = PMD), and 2-undecanone. If it’s not on this list but somebody claims it works, that person is probably trying to sell you something. Here’s a review by Consumer Reports.
- Spray your hiking clothes and favorite hat with permethrin. Once dry it not only repels mosquitoes, it kills insects on contact. Works against ticks, too. You can buy concentrated permethrin sprays at outdoorsy stores like REI (and online, of course). Sawyer is a popular brand. Permethrin activity survives a half-dozen washings, too, which is a really nice feature.
- Wear light-colored clothing. Mosquitoes target people wearing dark clothes. Sorry art majors. I’m just the messenger.
- Bathe regularly and don’t apply too much perfume. Mosquitoes rely heavily on body odor and fragrances. There are some species (e.g., Anopheles gambiae) that are especially fond of ankles and will thus use stinky shoes and socks as important cue.
- Avoid shampoos and lotions that contain lactic acid (mosquitoes use that chemical to find humans).
- Avoid drinking beer. That advice will be a non-starter for many, but research shows that people drinking beer are more attractive to mosquitoes. I’m assuming it’s the odor the beer causes (on a person’s breath) rather than the slower reaction times of drunk people, but the latter would certainly be adaptive for mosquitoes. I don’t know whether wine drinking is equally attractive to females. Please don’t misinterpret that last sentence.
- Avoid getting sunburned, something that will elevate your skin temperature due to the inflammatory response (“sunburn fever”). Higher temperatures cause mosquitoes to find you faster. In related news, so does being pregnant.
- Hanging bags of water from the rafters does not deter mosquitoes at all. Adding shiny pennies to the bags doesn’t help, either. Great conversation starter, though. Here’s a video touting the technique in case you’re curious (half a million views!). Apparently the belief in this is strong in the American South and south of the border. I’m not sure who started it. I took this photograph in Mexico.
- Plants sold as “mosquito-repellant plants” do no such thing per multiple scientific studies.
Protect cats and dogs
One noble reason to reduce the number of bites your pets get is to make their lives better, but the ultimate reason is that you don’t want those blood-engorged females laying eggs.
- Make a safety bed for your dog by spraying it with permethrin and placing in a place protected from rain. Once dry the permethrin will not only repel mosquitoes it can even kill those that foolishly land on the fabric. The permethrin will even stay active through multiple washings. If spraying a blanket is outside your skill set you can buy treated bedding online (Amazon, e.g).
- If your dog has a favorite spot to rest when outside, set up a fan or two like described above but plug it into a motion activated switch (Wemo makes them). Then when the dog arrives at the bed the fan kicks in and the mosquitoes are sucked to their deaths.
- Outside cats are hard to protect but if they have a favorite nap spot cover it with a box or some type of screened dome and coat the exterior with permethrin. Cats are rather sensitive to pyrethroids so it’s probably best to avoid spraying the inside of the box.
- Do not spray your pets with pyrethroids or DEET. They’ll lick themselves and then get sick.
If you have chickens in your yard you’re going to have a mosquito problem. While chickens are rather good at eating mosquitoes during the day, at night when resting they are completely passive and helpless and hundreds of mosquitoes will use that opportunity to fill up … and then lay thousands of eggs.
- Consider painting the interior walls white so that the chickens can better see resting mosquitoes. I have no proof this helps but it seems reasonable given that some mosquitoes just hang out on walls waiting.
- Spray the walls (interior and exterior), ceilings, and eves of the coop with permethrin. Again, the chemical will repel mosquitoes away from the coop and also kill insects that walk on the surface.
- If your chicken coop is well covered and has windows, put fans in opposite windows so there’s a directionality to flow and situate the roosts in between. Equip one or both fans with pyrethrum-coated screening (or tule) to receive the mosquitoes that are sucked or blown onto it. Ideally use metal screening that is spray-painted white so that the chickens can pick off the insects for snacks. The easiest way to attach screening is with a handful of neodymium magnets. Then it’s easy to pop the screen off for cleaning. Fans don’t need to be high-powered so explore solar options if your coop isn’t wired.
Make your yard less inviting
Mosquitoes like to hang out in moist shaded areas during hot days so you can encourage them to go elsewhere by thinning out the vegetation on your property. In particular, get rid of dense ground covers like English ivy, Japanese Pachysandra, and goutweed. These are invasive weeds so don’t feel at all bad about ripping them up — go with native ground covers that allow at least some sunlight and airflow to penetrate down to the soil level. Some mosquito species are especially fond of above-ground resting sites so also remove any English ivy growing on tree trunks and building structures.
Piles of logs, branches, and leaves can also provide hiding spaces for mosquitoes. These same piles might provide shelter for other organisms (some birds, e.g.) so you might need to make a judgement call on whether to remove them.
Also minimize the number of objects in your yard that might be providing shade and humidity. These might include old bathtubs, unused cars parked on the lawn, piles of lumber, and kid toys. I.e., if you or a neighbor has a hoarding problem you’re going to have mosquitoes.
Fog yard with insecticide
The nuclear option for mosquito control is to hire a pesticide company (Mosquito Shield, Mosquito Joe, etc.) to fog your property with pyrethroids. These synthetic neurotoxins kill mosquitoes extremely well but, unfortunately, kill almost everything else as well — monarch butterflies, honey bees, fireflies, etc. The spray will also kill animals on adjacent properties so you should never, ever do it without first talking with your neighbors. For more details, please see, “Effects of mosquito sprays on humans, pets, and wildlife.” FYI, for the same cost of a single season of spraying (perhaps $800) you can buy several dozen of the autocidal gravid ovitraps (listed above) and and then give them to everyone on your block — you’d be a hero.
And please don’t install automatic insecticide foggers. I can’t even.
Get your community involved
To truly knock back mosquito populations you need to involve not just your immediate neighbors but your whole community. So please share this page on Facebook and Nextdoor to reach as many people as possible.
Send me an email if you have questions or comments.
COPYRIGHT COLIN PURRINGTON