Mosquitoes – A disease concern?
by
Scott Reiter
Extension Agent, Agriculture and Natural Resources


The recent news coverage of the Zika virus spread in South America has concerned many residents. The Zika virus is not new. It was discovered in 1947 in Uganda, Africa. While over 500 cases have been identified in the United States they were not local transmissions. Most persons had traveled in South America and contracted the virus there. The Asian tiger mosquito (Aedes albopictus) is a vector of Zika, Dengue, and Chikungunya across the world. The Asian tiger mosquito is widespread across the U.S. but the Zika virus has not been detected in them at this time.

It is a well known fact that mosquitoes need standing water to complete their life cycle. Adult mosquitoes feed on animals and humans for a blood meal. These female adults then lay eggs on standing water. The eggs hatch into larvae or wrigglers that are often seen squirming about in still water. After growing for a few days these larvae pupate or begin the process of transforming into an adult. The entire process takes 10-14 for most of our common mosquitoes. There are numerous species of mosquitoes in our area. The control measures listed at the end of the article will help with all species.

Often, a nearby pond, puddle, flooded ditch, marsh, or swamp are the focus of the mosquito complaints. However, in most cases the problem mosquitoes turn out to be Asian tiger mosquitoes and the source of these mosquitoes is found to be containers of water on or near your property. These mosquitoes are black with white, tiger-like strips on their legs and body.

Asian tiger mosquitoes are what are known as a container breeder. Asian tiger mosquitoes will not lay their eggs in puddles, flooded ditches, natural ponds, marshes, swamps, or any body of water with a natural soil basin. Mosquito breeding containers of water can include: buckets, plastic cups, trash can lids or trash cans, ceramic or plastic plant trays, ornamental [plastic lined] ponds, old tires, boats, bird baths, wading pools, abandoned swimming pools, rain barrels, plastic toys, glass bottles or jars, clogged roof gutters, corrugated black plastic downspout extension pipes, and tree holes [i.e., knot holes or forks in tree trunks that hold water]. In shady neighborhoods, trees reduce the amount water evaporation from their aquatic "container" habitats by providing shade and reducing air flow. A container holding a gallon of water and sitting in the shade will still hold water months later even if there has been no rain. An Asian tiger mosquito larva can complete its development into an adult biting mosquito in as little as a tablespoon of water.

Asian tiger mosquitoes are only active during daylight hours but do not like to spend too much time in open sunlight. Therefore, their populations are more of a problem in neighborhoods that have a lot of shade. Tiger mosquitoes spend a lot of time sitting in the foliage of a bush or shrub, waiting for a person, cat, or dog to walk by before they fly out to bite. They are persistent in their attempts to feed, but they are cautious and sneaky, preferring to bite ankles, backs, and the back sides of arms and legs. Asian tiger mosquitoes can be a potential health threat as they are able to transmit a number of mosquito-borne diseases. In Virginia, these diseases include West Nile virus, La Crosse encephalitis, and Eastern equine encephalitis.

The best tiger mosquito control efforts involve people going around their property to find and dump all the container breeding habitats. Insecticide treatments provide some value but are not a season long solution. Insecticides used to treat standing water provide good control of larvae. However, draining or dumping that water is a much better option! Personal repellents are the first line of defense when mosquitoes are a concern. Products containing DEET or picaridin provide the highest levels of protection. Be very wary of home remedies as they may be more injurious than helpful. Items such as bug zappers, ultrasonic devices, outdoor foggers, and certain plants have limited effects on overall mosquito populations or limited research on usefulness.

For more information call your local Virginia Cooperative Extension office.

Extension is a joint program of Virginia Tech, Virginia State University, the U.S. Department of Agriculture, and state and local governments. Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer.