Below are some tips for reducing the number of mosquitoes in your yard.
Eliminate standing water
Mosquitoes can develop in as little as 1 teaspoon of water in as little as 4.5 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 of the objects to remove, regularly empty, or alter in some way (e.g., drill drainage holes) so that they cannot accumulate water.
Other objects of concern are: pool covers, pot saucers, grill covers, plastic kid toys, tires, unattached hoses, empty glazed pots, shovels, construction materials, garbage cans, garbage can lids, containers in recycling bins, bottle caps, cemetery vases, decorative shells, empty coconuts, papaya tree stumps, downspout troughs, spigot drips, ollas, pickup truck beds, window wells, septic tanks, uncapped metal fence posts, animal tracks.
And some mosquito species can complete their life cycle in containers found 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).
Kill larvae with Bti
If you have items that are supposed to hold water, add cakes (e.g., MosquitoDunks) or granules (e.g., MosquitoBits) 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 (see movie) 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. 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 treat with Bti:
Additional sites that need regular Bti treatment are: rain barrels, sub-irrigated planters, water features, water gardens, 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. Note that some of these locations might be off of your property, so you might need to be proactive to get others (neighbors, town officials) involved.
One note about low areas in your yard that sometimes flood: some species of mosquitoes oviposit in such areas and have eggs that can survive for years. So when your yard has that rare flooding event, years of accumulated, waiting eggs will hatch all at once. In situations like this you should be especially vigilant about adding Bti granules and cakes.
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.
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 too cheap to buy lures you can experiment with old socks and smelly cheese (Limburger type), which work to attract some species of mosquitoes.
- 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 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.
- 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 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 be blown onto the pyrethrum-coated screening where they will die. Please see the diagram in “Protect your chickens” near the bottom of this page for a visual.
- If you have screen doors, another easy DIY trick is to paint or spray the exteriors with permethrin. Then when mosquitoes land on the 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.
- A related DIY tip is to paint the trim of windows and doors with paint dosed with pyrethroids (e.g., Bug Juice, M-1). Mosquitoes love to alight on door and window jambs because CO2 and human odors are leaking out at these locations. They are waiting for an opening, and while they wait they’ll be slowly getting a lethal dose of insecticide. If you live outside the United States you can often buy paint that already has insecticides (Inesfly features time-release insecticidal paint).
Make yeast-based traps that emit carbon dioxide and attract mosquitoes. No, don’t do that. Just another myth that’s gone viral because somebody posted instructions to YouTube.
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 (e.g., Aedes) 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. At right are traps sold by BioQuip and Springstar. Per multiple studies that deploy this traps in the real world, they reduce mosquito numbers substantially. So get at least four for a typical yard.
You can also make these traps rather cheaply if you’re handy (instructions). 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. You want everyone on the block to get these so post your kills to Facebook so your neighbors burn with envy.
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.
To avoid the Bti concern, add screening to the trap so that larvae can develop but the adults become trapped. There are excellent instructions on how to cheaply make these on Instructables by jfulop10 (photo at right).
More trap ideas here from scientist in Hawai’i: http://makemosquitotraps.org/.
Protect yourself from bites
- 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. Victoria’s Secret Bombshell is a good repellent, too, which is rather convenient if you’re not wearing much, I guess. Here’s a review by Consumer Reports.
- Spray your hiking clothes, boots, backpack, and favorite hat with permethrin. Once dry it not only repels mosquitoes it kills insects on contact. Works against ticks, too. You can buy 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. Mosquitoes rely heavily on body odor to find humans. 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. Higher skin temperatures (from inflammatory response to burn) 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.
- Plants sold as “mosquito-repellant plants” do no such thing per multiple scientific studies. Also avoid wrist bands, citronella candles, and herbal repellents — all have very devoted fans on internet but they don’t work at all.
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.
Protect your chickens
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.
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. In nature it is thought that bats really don’t eat that many mosquitoes. Mosquitoes are just too small to bother with when moths and such are abundant.
- Dragonflies will eat mosquitoes so constructing a small pond in your yard to attract them might be fine. But it’s generally thought dragonflies’ ability to control mosquitoes is completely exaggerated. For example, dragonflies don’t feed at night when most mosquitoes are active.
- Swallows, purple martins, and barn swallows will eat some mosquitoes during the daytime but not really enough to make a difference. Claims to the contrary are popular but not based on scientific evidence.
- Other insects and spiders are probably the primary consumers of mosquitoes, and they are too numerous to list. I’d bet good money that jumping spiders (Salticidae) are especially important. I don’t have any evidence to support this belief but two species of jumping spiders 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.
Make your yard less inviting
Mosquitoes like to hang out in moist shaded areas during hot days so you can encourage them to leave your yard by thinning out the vegetation on your property. In particular, get rid of dense ground covers such as (non-native) English ivy, Japanese Pachysandra, and goutweed. All of it. Replant with (native) ground covers that typically 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 all the English ivy growing on tree trunks and buildings.
Piles of logs, branches, and leaves can also provide moist, shaded 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. But if you really want a mosquito-free yard, you know what to do.
Also minimize the number of man-made 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 thousands of mosquitoes waiting for you to come outside.
Finally, wean your garden off of sprinklers on timers. If an area gets a frequent watering (daily, or every other day), the vegetation there will become an ideal place for mosquitoes to hang out. Opt for drip irrigation or hoses that seep, instead.
Fog yard with pesticides
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, mason bees, fireflies, moths, 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 (vendors listed above) and hundreds of MosquitoDunks … 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 consider sharing this page on Facebook and Nextdoor. Nudge your neighbors to be proactive and your elected officials to help get the word out. People in some towns create a Facebook group for sharing control ideas.