West Nile virus, dengue fever, malaria, yellow fever, encephalitis: quite a list of reasons not to like the mosquito, isn’t it? Not to mention the itching and inflammation caused by their bites. Though your chances of contracting malaria in the United States are minimal, other mosquito-borne diseases are indeed a threat. The Centers for Disease Control and Prevention (CDC) reported nearly 4,000 confirmed cases of dengue fever in the country between 1995 and 2005. Add to that the 720 confirmed cases of West Nile virus (the leading cause of arboviral encephalitis) in 2009 and it’s enough to make you want to run for the spray can. But an adequate understanding of these little critters can lead to safer and more effective methods of control.
Mosquitoes are not a garden pest, but rather a pest of the gardener. More than 150 species of mosquito may call your North American back yard home. All are true flies and spend most of their time feeding on plant nectar. Only the females supplement this diet with the blood of animals or birds, which provides the protein necessary for egg maturation. Adult females lay eggs on the surface of stagnant water. Four to fourteen days later, the eggs hatch into wriggling larvae that begin to feed on water-dwelling microorganisms including fungi, bacteria, and algae. The larvae then pass through several life stages, called instars, before pupating into adults. Depending on the species, adults can live from a few weeks to several months.
Controlling mosquitoes starts with getting rid of standing water. Regularly empty and clean birdbaths, drain pot saucers, and clear clogged gutters. Stock ponds with larvae-gobbling fish and set up a pump to provide constant circulation. Treat water barrels and smaller water features monthly with Mosquito Dunks, floating donut-shaped cakes containing the organic larvicide BTI (Bacillus thuringiensis var. israelensis). Hang a bat house (each adult can eat several hundred mosquitoes every night); put up birdhouses for chickadees, wrens, purple martins, and other insectivorous species; and encourage frogs, toads, and dragonflies to take up residence by installing a buffer of tall grasses and native plants around ponds and streams.
And, if necessary, protect your skin with repellents based on oil of lemon eucalyptus. Brands such as Repel and Cutter Lemon Eucalyptus are derived from the native Australian lemon-scented gum tree (Corymbia citriodora, syn. Eucalyptus citriodora). It is the only plant-based control recommended by the CDC, and it’s safe, effective, and 100 percent natural. The citronella-scented geraniums you might find advertised as mosquito detractors are lovely plants, but there’s no proof they keep insects at bay.