Mosquito Prevention Resources

Dump Standing Water!

Mosquitoes need standing water in order to complete their lifecycle. They lay their eggs in still water and can go from egg to biting adult in as little as 5 days! This is why it is important to check regularly for standing water in and around our homes and to dump out or treat any water we find. 

 

 

Mosquitoes lay their eggs in standing water. Some mosquitoes can lay their eggs in as little as 1/4” of water and can lay hundreds of eggs at a time—so even very small sources can become a big problem.

 

The eggs then hatch into larvae which live in the water. These larvae look like small worms. Dump water immediately if you see larvae.

 

 

 

Adult mosquitoes  emerge from the water and start biting. Mosquito bites can leave painful welts and
some mosquitoes can spread diseases caused by the West Nile, Zika, dengue, and yellow fever viruses.

 

Dumping out standing water and keeping containers dry is the most effective way to control mosquitoes around your home.

 

Download and share our Dumping Out Standing Water Flyer (pdf)

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Mosquito egg raft photo by Harry Weinburgh, CDC
Adult mosquito photo by James Gathany, CDC
Bucket pouring water photo by Lauren Bishop, CDC

Common Backyard Sources

Mosquitoes lay their eggs in standing water. Here are some common sources of mosquito breeding in backyards to keep an eye out for. Check these places weekly for standing water and dump it out or treat it with a bacterial larvicide.

 

Get started with your home mosquito inspection by looking for these common sources of backyard mosquito breeding!

  • Flower pot saucers
  • Buckets and containers
  • Fountains
  • Open trash cans
  • Outdoor furniture
  • Rain Barrels
  • Tarps
  • Kid's Toys
  • Kiddie Pools
  • Wheelbarrows
  • Birdbaths
  • Watering Cans

 

 

Download and share our Guide to Common Backyard Sources (pdf)

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Rain Barrel

Keep mosquitoes out of your rain barrel! Rain barrels can be a great way to conserve water, but all that water can also become a major breeding source of mosquitoes. Keep openings into your rain barrel screened off and treat rain barrels regularly with a bacterial larvicide to prevent mosquitoes.

 

 

 

Cover inlet and outflow openings with mosquito proof screen (1/16th inch mesh). This will prevent adult mosquitoes from entering the barrel to lay their eggs.

 

 

 

 

 

 

Add a bacterial larvicide (liquid, dunk, or granule) to the water in the barrel monthly according to the label. Larvicides kill mosquitoes but are safe for people, plants, and animals.

 

 

 

 

Keep barrel, screens, gutters, and downspouts free of debris. Regularly inspect for cracks or leaks to prevent puddles from forming around the base of the rain barrel.

 

Download and share our Guide to Rain Barrels (pdf)

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Rain Barrel Screen photos by Christine Hennessey

Green Pools

Keep mosquitoes out of your pool! Green backyard pools are major breeding sources of mosquitoes that spread diseases like West Nile virus. Maintain your pool to keep it from breeding mosquitoes. Report green pools to the Vector Control Program.

 

 

Mosquitoes will not breed in pools that are filtered and chlorinated. Maintain your filtration system including the pump and filter regularly and add chlorine as recommended.

 

 

 

Even drained pools can collect enough water when it rains to attract mosquitoes. Ensure all the water drains from the bottom of the pool or add mosquito fish or bacterial larvicide. Mosquito larvae can live in as little as 1/4" of water. 

 

 

 

Mosquito fish (available free of charge from the county) can be placed in ponds and pools to control mosquito larvae.  For a list of locations you can pick up fish, visit bit.ly/mosquitofishsd.

 

 

 

Bacterial larvicides containing Bti (like Mosquito Dunks) kill mosquito larvae but are harmless to people, pets, and wildlife.  They are sold online and at hardware and garden stores.

 

Download and share our Guide to Pools (pdf)

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Drainage

Keep mosquitoes out of your drainage system! Systems designed to drain water away from our homes can often retain water if they are clogged, damaged, or not set up optimally. Even 1/4” of water at the bottom of a drain or pipe can become a source of mosquito breeding!

 

 

Clean out leaves and other debris in gutters
regularly. Flush the pipes after cleaning. Downspout extenders can also retain water —remove them or tip out any remaining water after it rains. 

 

 

 

Lawn drains, French drains (a very common sources of mosquito breeding), and other drains
and pipes can retain water. Flush these drains
regularly and treat standing water with a bacterial
larvicide regularly according to the label.

 

 

 

Check covered drains regularly for standing water. Use a flashlight to check  drains—a reflection means there is pooled water. Clear clogs or treat standing water with a bacterial larvicide regularly.

 

Download and share our Guide to Drains (pdf)

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Septic Systems

Mosquitoes can lay hundreds of eggs inside broken or improperly sealed septic tanks.  Inspect septic tanks regularly to look for missing covers, cracks, gaps in blocks, or missing screens and perform any necessary repairs.

 

 

Cleanout access above the septic tank should be sealed and watertight. Makeshift lids, cracked PVC caps or broken/cracked concrete lids should be replaced and edges should be sealed tightly. Mosquitoes can slip through evern small cracks. 

 

 

 

Any saturated/wet ground because of drain field failure will act as a mosquito breeding ground and should be treated immediately with a bacterial larvicide containing Bti.

 

 

Ventilation pipes should be securely covered with screening. Observation pipes should be capped
with a removable cap. Form the screen into a cone
if the vent pipe is below or near a tree.

 

Download and share our Guide to Septic Systems (pdf)

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Cleanout access photo by Adriana W. Van Leeuwen
Septic ventilation pipe screen photos via Marin/Sonoma Mosquito & Vector Control District
Open ventilation pipe photo via Centers of Disease Control and Prevention (CDC)

Sump Pumps

Keep mosquitoes our of your sump pump! Mosquitoes can lay hundreds of eggs inside your sump pump’s reservoir! Sump pumps are designed to pump water from underneath the house, but often hold small amounts of water that can breed mosquitoes.

 

 

 

When water reaches a certain level in the sump
pump basin, the float rises, switching on the pump.  Small amounts of  water in the basin will not trigger the pump and can attract mosquitoes.

 

 

 

 

Large openings create easy access for mosquitoes
to access water inside sump pumps. Cover holes
with fine mesh screen to keep mosquitoes out.

 

 

 

Prevent larvae from developing inside the basin, and control larvae that have already hatched by treating with a bacterial larvicide containing Bti such as Mosquito Dunks.

 

Download and share our Guide to Sump Pumps (pdf)

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Potted Plants

Keep mosquitoes our of your potted plants! Invasive Aedes mosquitoes will lay their eggs in as little as 1/4” of water. Even the small amount of water that collects in the saucer under a potted plant is enough to cause a mosquito problem. Follow these tips to prevent mosquitoes.

 

 

Avoid overwatering plants. Dump out excess water that collects under the pot after watering or after rain. Keep the saucer dry or dump the water out once a week.

 

 

Filling saucers with fine gravel or sand can make it more difficult for mosquitoes can lay their eggs. The rocks or sand should go high enough that there is no visible water surface.

 

Invasive Aedes mosquitoes lay their eggs on the side of containers. Wiping out saucers and the outside of pots with a sponge can help to remove eggs.

 

 

Don’t leave unused pots and saucers outside where they can collect rain water and debris.  Store them inside or upside down.

Download and share our Guide to Potted Plants (pdf)

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Potted plant with sand photo by Delta Vector Control District

Bromeliads

Keep mosquitoes our of your bromeliads! Bromeliads are tropical plants that naturally collect water between their leaves. Even this small amount of water is enough for a mosquito larvae. Avoid planting bromeliads, or use these tips to prevent mosquito breeding.

 

Water bromeliads at the base so that the tanks do not fill up with water. Or, regularly flush out the water collected between the leaves(this part is called the tank of the bromeliad) with a hose (at least once a week) to remove mosquito larvae.

 

 

Sprinkle a bacterial larvicide into the water between the leaves of the bromeliad regularly as directed by the label. This kills mosquitoes but is safe for people, plants, and animals.

 

 

For potted bromeliads, tip them over to drain the
water once a week. Dump out any water in saucers
under potted plants once a week as well.

 

 

Inspect bromeliads for larvae regularly to be sure control measures are working. Larvae look like small wiggling worms. Shining a flashlight into the plant can help you see them.

Download and share our Guide to Bromeliads (pdf)

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Indoors

Keep mosquitoes out of your home! Invasive Aedes mosquitoes will lay their eggs in as little as 1/4” of water—even inside people’s homes! Dump standing water inside and outside to
prevent mosquitoes from biting you inside your home.

 

 

Vases and Decorations : Dump out water kept in vases or other containers weekly.  Keep indoor fountains running or leave them dry. Mosquito larvae can live in as little as 1/4" of water. 

 

Indoor plants: Dump out any water in house plant saucers weekly. Change out water for plants  that grow in water like lucky bamboo weekly. Do not over water plants. Moist soil can attract fungus gnats—a harmless insect that is  sometimes mistaken for a mosquito.

Things like pet bowls, drains, toilets, un-filtered aquariums, and dirty dishes do not usually breed mosquitoes but can if they are left full of  water for more than a week without being changed or drained.  

Download and share our Guide to Indoor Sources (pdf)

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Flower vase photo by David Condrey via Pixabay

Indoor potted plants photo by Luis Fernandez Garcia via Wikimedia Commons

Children's Toys

Keep mosquitoes out of your children's toys. Many common items found in your backyard can breed mosquitoes, including children’s toys! Toys left outside can collect water, so make sure to store them properly and follow these tips to prevent mosquito breeding.

 

 

 

Toys left outside can collect water. Even stored
upside down some small amounts of water may still collect in the toy. Store toys indoors or under covered areas to keep water from pooling.

 

 

Toys that require water, such as water tables and kiddie pools, should be dumped out at least once a week, kept clean, and stored or covered when not in use to avoid collecting rainwater.

 

 

Water can collect in places where it is difficult to see such as tires and even the bases of basketball hoops. Drill drainage holes in tire swings and any play equipment that can hold water. Make sure openings into the bases of basketball hoops are securely sealed.

Download and share our Guide to Children's Toys (pdf)

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Toy truck photo by Chris (urbanmystic 5719) via Flickr
Kiddie pool photo by Elias Gayles, via Flickr
Tire swing photo by Alan Levine via Flickr

Cryptic Sources

Mosquitoes can lay their eggs in as little as 1/4” of water, so the source of a mosquito problem can be difficult to locate. Here are some examples of small and often overlooked cryptic mosquito breeding sources.

 

 

Tree holes, as well as holes in soil or cement can collect enough water to breed mosquitoes. Fill these holes with sand, cement, or soil to prevent water from pooling.

 

 

 

Uncapped fenceposts and bamboo poles can
collect rain water quite easily. Cap fence posts
or fill these holes with sand or cement.

 

 

Clutter like old tires, bottles and cans, or old pots
or buckets can also hold enough water to breed
mosquitoes. Throw away what you can, and cover the rest tightly with a tarp.

Download and share our Guide to Cryptic Sources (pdf)

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Questions?

  (858) 694-2888

  vector@sdcounty.ca.gov