Master Gardeners of Northern Virginia

Over 40 Years of Growing Gardens and Gardeners

Phlox Subulata (moss pink) in landscape. Photo © Elaine Mills

Restoring Nature Action 5:
Manage Mosquitoes Without Harming Pollinators

by Joan McIntyre, Elaine Mills, & Leslie Cameron, Extension Master Gardeners

Logo of 'Restoring Nature' by MGNV featuring green and white colors with a plant icon.

Nature is in trouble, but we can all play a role in helping to restore essential ecological services in our urban and suburban landscapes, including those of us with modest garden space.

Mosquitoes are a nuisance when we are outside in the summer, and more importantly they can carry disease. But before reaching for the spray or hiring a company that uses aerosol pesticides, consider that these pesticides don’t just kill mosquitoes. They target all insects that come into contact with the chemicals, contributing to the decline of pollinators and other beneficial insect populations. Action 5 in our Restoring Nature series offers strategies for managing mosquitoes without harming pollinators.

Understanding Mosquitoes and Their Life Cycle

Close-up of a mosquito feeding on human skin, with its proboscis inserted.
Culex pipiens Mosquito
L: A female Aedes aegypti mosquito feeds on a human host Photo via Flickr
R: Culex pipiens (northern house mosquito) Ary Farajollahi, Bugwood.org

With spring and warming temperatures come mosquitoes. Hibernating females become active in late spring when temperatures reach a consistent 50 degrees Fahrenheit. Spring is a good time to put strategies in place to reduce their population. With each female laying hundreds of eggs and with a new generation every 7-10 days, a single female can trigger hundreds of thousands or even millions of mosquitoes within a few generations. The more mosquitoes controlled early, the fewer there will be later in the summer.

A birdbath sitting on a decorative stand, surrounded by lush green ground cover and foliage in a garden.
Bird baths attract female mosquitoes. Photo © Elaine Mills

Among the most common species in our area, Aedes albopictus (Asian tiger) mosquitoes are most active and most likely to bite during the day. Asian tigers are native to Southeast Asia and may have arrived in North America in shiploads of tires. First documented in the U.S. in 1985, the Asian tiger has spread widely and is now the number one source of bites in Virginia. Another common species, Culex pipiens (house mosquito), is most active and most likely to bite at dawn or dusk.

Female mosquitoes need standing water to breed. It’s the females that bite, and they bite for a blood meal, which they need to lay eggs. The eggs hatch, go through larval and pupal stages, and then emerge as adults in as little as 7-10 days. Asian tiger females lay their eggs in both artificial habitats, like buckets or birdbaths in our yards, and natural habitats, like tree holes. Asian tigers in particular have adapted well to our urban and suburban neighborhoods, because there are so many artificial sources of standing water.

Controlling Mosquitoes: What Works and What Doesn’t

A few mosquitoes in spring multiply rapidly to many million later in the summer. Start controlling them in the spring to reduce the numbers later.

What Works

Mosquitoes are best controlled at the larval stage, not as adults.

  • Step 1: Eliminate breeding sites by removing temporary standing water every seven days. Females can lay eggs in very small amounts of water—even a tablespoon or so—and our yards have more water sources than we think they do. Here are a few places where water can collect: birdbaths, leaky hoses, wagons, toys, kiddie pools, pet dishes, upturned tools, watering cans, buckets, wheelbarrows, saucers under plants, and the ends of corrugated downspouts. Make sure gutters run clear. Old tires and tarps can also collect water. Dump water every seven days, or add Bti (Bacillus thuringiensis israelensis), the active ingredient in mosquito-control products. Bti kills mosquito larvae but doesn’t harm birds or other wildlife.
  • Step 2: Set up one or more mosquito larva or lethal oviposition traps. Commercial traps are available, but an easy and less expensive alternative is a DIY trap bucket. To create a DIY trap, add a good three or four handfuls of straw or dry vegetation to a large bucket (a handful or two to a smaller bucket), fill halfway with water, and add a Bti product, like Mosquito Dunks®. Use dunks not bits. Mosquito Bits® are quick kill, and the bucket works better with slow release. To keep animals out, add a piece of hardware cloth or chicken wire on top. As the straw ferments, it attracts female mosquitoes, who lay their eggs in the bucket. The eggs will hatch, and the Bti will kill the larvae. Add a new dunk once a month. The Northern Virginia Bird Alliance has instructions on how to construct your own DIY trap. Entomologist Doug Tallamy explains how to set up a trap and why it works in this short video.

In addition to reducing mosquito populations at the larval stage, we can protect ourselves from the adults:

  • Wear long pants and long sleeves.
  • Use an insect repellent, like DEET (25–30 percent—not for use on infants or cut or irritated skin), picaridin (20 percent), oil of eucalyptus, or IR3535® (ingredient in Avon’s Skin So Soft Bug Guard). 
  • Make sure screens don’t have holes.
  • Use fans on a patio or deck to keep mosquitoes at bay—mosquitoes are weak flyers.
  • Apply permethrin on clothes only (not skin), or buy clothes pretreated with permethrin.

What else can we do?

Two trees surrounded by lush green ivy on a grassy slope, with a stone wall and building in the background.
Slope covered in English ivy. Photo © Elaine Mills

What Doesn’t Work  

Using aerosol pesticides to target adult mosquitoes is the most expensive and least effective strategy. According to Doug Tallamy, yard and area fogging treatments kill at most 10 percent of adult mosquitoes. Remaining mosquitoes repopulate quickly, so pesticide companies need to return over and over. There is also evidence that mosquitoes are developing resistance to the chemicals.

In addition, these aerosol pesticides are nonselective and target many other insects, including pollinators, mosquito predators like dragonflies and damselflies, and other beneficial insects. Most mosquito spray companies use pyrethroid-based aerosol pesticides (under many brand names). Pyrethroids are synthetic chemical insecticides that mimic some of the features of pyrethrins, a naturally occurring pesticide derived from chrysanthemum flowers. But despite how these may be marketed, pyrethroids are synthetic, do not “come from” chrysanthemums, and are not “natural.”

Other products and strategies that aren’t effective include:

  • Bug zappers
  • Spraying Listerine
  • Wearing dryer sheets, Vicks VapoRub, or vanilla extract
  • Mosquito-repellent wristbands or ultrasonic devices
  • Plants marketed as “mosquito repellent”
  • Propane-driven CO2 emitters
  • Bats or purple martins
  • Eating garlic

For more information about controlling mosquitoes at the larval stage, protecting ourselves from adults, and the downsides of using aerosol pesticides, visit Protecting Yourself from Mosquitoes Without Harming Pollinators.

SMALL SPACE MOSQUITO CONTROL TIPS:

Residents with small spaces, including those in townhouse communities or condo associations, can do a lot to reduce mosquito populations.

Locate standing water in your patio, on your balcony, or in other small spaces and dump it every seven days, or add a Bti product, like a mosquito dunk once a month.

Recommend these steps to your board, property manager, or grounds/landscaping committee:

  • Make sure gutters are running clear.
  • If the community uses corrugated downspouts, replace these with metal or other smooth-surfaced downspouts.
  • If common-area drains hold standing water, add a Bti product (like a mosquito dunk) once a month.
  • Check any flat roofs for standing water, especially after rain, and if water can’t be drained add a Bti product once a month.
  • Regularly share information with residents on mosquito controls that work.
  • Prohibit the use of aerosol pesticides by the community or individual residents. Share information on how these pesticides harm many beneficial insects. Controlling mosquitoes at the larval stage is much more effective.
A black bucket with a wire mesh lid surrounded by green plants in a garden setting.
DIY Mosquito larva trap in a 1 gallon bucket. Photo © Leslie Cameron

Most “recipes” for mosquito larva traps recommend using a 5-gallon bucket, but smaller options work just as well. Most big-box hardware stores carry 1- and 2-gallon buckets in their paint sections. Put a handful or two of straw in the bucket, fill it halfway with water, add a half or quarter of a Bti “doughnut” or mosquito dunk, and, to keep animals out, add a piece of hardware cloth or chicken wire on top.

Set up one or more mosquito larva trap buckets, and get your neighbors involved! For those in densely populated communities, the mosquitoes a couple of doors down are close to you. The more buckets in a neighborhood, the better.

Master Gardeners of Northern Virginia (MGNV) Resources

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