Photo: Eastern Bluebird, Laurie Lawler, Great Backyard Bird Count
It’s summertime and mosquito control companies are once again pushing their services to kill mosquitoes in your yard. Although the companies may claim they target only mosquitoes, the products they use have a broader impact. The products kill mosquitoes but they also kill other insects and insect larvae that birds, reptiles and amphibians rely on as essential food sources. Over the last 50 years North America has lost over 3 billion birds. Habitat loss is the primary driver of avian decline, but loss of a food source in an area is also loss of habitat. The good news, if you are plagued by mosquitoes, is that there are easy, non-toxic ways to reduce the population in your yard.
Services we contacted in Northern Virginia use sprays containing pyrethrins or their synthetic form, pyrethroids, to kill mosquitoes. The products are not selective for mosquitoes but can kill all insects and arthropods (spiders, mites, centipedes and millipedes). The material safety data sheet (MSDS) for a product one local company uses lists the pyrethroid Bifenthrin as its active ingredient. The MSDS shows that the product can be used to kill not only mosquitoes, but also ants, bees, wasps, hornets, beetles, centipedes, cicadas, crickets, flies, gnats, moths, spiders, spider mites and fruit flies, among other insects and arthropods. The MSDS specifies that the product is extremely toxic to fish and aquatic invertebrates and is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds.
Fortunately, there are non-toxic alternatives that can control mosquitoes. Removing stagnant water and other materials that can be a breeding ground for mosquitoes is not difficult and doesn’t harm other insects or arthropods.
Identify and empty out any outdoor containers that can accumulate water, including saucers under pot plants.
Store other containers that could accumulate water such as wheelbarrows, watering cans and recycle bins in a shed or garage.
Clean out bird baths and replace the water regularly. Adding an aerator also discourages mosquitoes.
Fix any leaking outdoor faucets that can cause puddles.
Clean out clogged roof gutters.
If your yard has any tree stumps with hollowed-out areas, fill them with dirt or mulch.
Eliminate flexible downspout extenders, which accumulate water in the corrugations even if they are pointed downhill. Consider installing a rain garden as an alternative to manage excess storm water runoff. A properly installed rain garden drains in 12 to 48 hours and the absence of standing water prevents breeding mosquitoes.
Cover any rain barrels with screening to prevent mosquitoes from entering to lay eggs.
If your yard has containers that can’t be emptied out, covered or turned over every week, such as septic tanks, pools not in use, or ornamental ponds without fish or amphibians to eat larvae, the Center for Disease Control and Prevention (CDC) suggests adding Bti, or Bacillus thuringiensis israelensis. Bti is a bacteria found in soil that produces toxins that kill mosquito larvae, blackflies and fungus gnats when they eat it. See the CDC Fact Sheet on Bti. It comes in a variety of forms, including Mosquito Dunks®.
Other possible sources of breeding mosquitoes may not be as obvious.
Thin out heavy ground cover (such as invasive English ivy) which can also provide a mosquito breeding ground.
Manage compost piles to discourage mosquitoes. Mosquitoes are attracted to discarded fruit and nectar-containing flowers. Stir in newly-added materials to the middle of a pile to accelerate decomposition and to avoid attracting mosquitoes and other pests. See "Compost Piles and Mosquitoes.”
Passive mosquito traps can provide additional protection and they do not use pyrethroids. Examples include the Biogents GAT, or the Autocidal Gravid Ovitrap, developed by the Center for Disease Control and Prevention and marketed as the BioCare AGO. They lure and trap egg-laying mosquitoes.