There are more than 2,500 species of mosquitoes, approximately 200 in the United States. At best, these flying pests are annoying to both man and beast. Some mosquitoes, however, can transmit diseases, such as malaria, encephalitis, yellow fever and West Nile virus (see References 1). Although the application of pesticides on lawns will kill mosquitoes, these agents can pose risks to human health and the environment. According to the U.S. Environmental Protection Agency, listed biological pest controls are safer than conventional pesticides (see References 2).
Certain plants contain volatile oils that repel and kill insects. Organic lawn and garden products formulated to counter mosquitoes often contain a combination of plant oils, including the essential oils of rosemary, thyme, peppermint, sesame, wintergreen and thyme. Other less familiar sounding botanical agents include eugenol from cloves and 2-Phenylethyl-propionate from peanuts. (See References 3)
Microbial pesticides are naturally occurring microorganisms, such as fungi or bacteria. The most commonly-used microbial pesticide is Bacillus thuringiensis, each strain of which produces a unique combination of proteins that target and bind to gut-receptor cells of insect larvae as they feed, causing them to starve. Products labeled as microbial pesticides intended for the management of mosquitoes contain strains or subspecies of this bacterium that are specific to mosquito larvae; they are applied as dusts, granules or sprays. (See References 4, "Biopesticides")
Certain predatory insects may help eliminate the ones that bug you. For example, the praying mantis feeds on mosquitoes, as well as other common lawn and garden pests. The American Mosquito Control Association says there is anecdotal evidence that dragonflies reduce the adult mosquito population (see References 5).
Another weapon in the war against mosquitoes on the ground is to fight from the air. Many of the more than 1,200 species of bats aggressively hunt flying insects. According to Bat Conservation International, a single brown bat can eat up to 1,000 insects per hour (see References 6). To employ bats as a natural mosquito control, you must purchase or build bat houses for them to roost in. BCI cautions that buying or relocating adult bats to your yard is not likely to be successful and is illegal in some areas (see Resources 1). Bats will usually occupy a well-constructed and strategically placed bat house within one to two years, although it can take as long as five years (see Resources 1).