Life History
Immature mosquitoes are worm-like larvae, known as wrigglers, that live in shallow water and fed mostly on microorganisms. They prefer areas protected from wave action by vegetation and floating objects. Mosquitoes rarely breed in moving water.
Only female adult mosquitoes feed on blood. Male mosquitoes feed on nectar and are not considered pests.
Management of Mosquito Larvae
The key to mosquito control is larval management. Larvae occur in specific areas and can be controlled by modifying the habitat through drainage, or with insecticides applied to larval breeding sites. Treatments provide control before the biting adults appear and disperse from the breeding sites. Mosquito control measures must be cost effective and environmentally sound. Consider alternatives before application of conventional chemical insecticides.
Habitat modification
Eliminating breeding sites, or habitat modification, is an effective and long-term solution. Sites can be drained or removed. Mosquitoes can breed in important wetlands, so habitat modification may not always be an option.
Any low, damp soggy area or ponds can create a breeding environment. Farm impoundment, seepage from irrigation pipe, standing water in control structures, irrigated pastures, and clogged ditches are all potential mosquito breeding areas. To control mosquitoes:
1. control seepage
2. reduce or eliminate vegetation and debris in ditches and other water containment structures; and
3. eliminate mosquito habitats in impoundments. Fill or drain depressions or other water-holding areas in impoundments, and fill or deepen shallow areas preferred by mosquito larvae.
Natural predators
Fish, dragonfly nymphs and diving beetles are natural predators of mosquito larvae while dragonflies, birds and bats feed on adult mosquitoes. The mosquito-eating fish Gambusia (closely related to guppies) can be reared in large numbers and released in mosquito breeding sites. Gambusia feed on many kinds of insect larvae, but prefer wrigglers and other top feeders. Mosquito fish have to be released annually in habitats that do not have year round water.
Insecticides
Microbial insecticides, especially the bacterial product known as Bti (Bacillus thuringiensis israeliensis) (Bactimos, Skeetal, Teknar, Vectobac, etc.) can be as effective as chemical insecticides. Bti is toxic only to mosquito and midge larvae. It is not hazardous to nontarget organisms, but can reduce midge populations that serve as fish food.
"Soft" chemical insecticides, such as the insect growth regulator methoprene (Altosid), are toxic only to insects and other arthropods. They are similar to certain insect hormones and create imbalances in the levels of hormones needed for proper mosquito growth and development. They do not directly harm fish or other wildlife, but can reduce the amount of available food.
Mosquito larvae also can be controlled by chemical insecticide applications to the water where they occur or are suspected to occur. Remember, several alternatives to conventional chemical larvicides have been developed because of concerns about applying chemicals to water that might be used for drinking or that contains fish and other aquatic life.
Questions to Ask Before Applying Mosquito Insecticides
What is the identity of the pest?
There are many insects that look like mosquitoes. Some mosquitoes do not feed on humans or transmit diseases. Different species have different larval habitats.
When should the pesticide be applied?
Adulticide and larvicide applications should not be automatic. Establish treatment thresholds and make applications only after counts of adults and/or larvae exceed these thresholds. To count larvae, collect them in white dippers in which they can be easily seen. Adults can be monitored with special light traps.
Where should the pesticide by applied?
Apply only to areas where mosquitoes are present. Target these areas by mapping breeding sites and adult resting sites.
What pesticide should be used?
Several insecticides are registered for use against mosquito larvae. Each has advantages and drawbacks. There are also several insecticides registered for adult mosquitoes. Caution: Adulticides may not be registered for use on food crops. Applications in residential areas can result in illegal residues on produce from home gardens.
Management of Adult Mosquitoes
If larval control fails, adult mosquito control may be necessary. Adult control generally is accomplished with insecticide applications using ground equipment or aircraft. Since mosquitoes are strong fliers, adult control is most effective if it is done over a large are or on a community basis. Because of the environmental hazards associated with wide-area insecticide applications, it is important for the community to agree on the criteria used to decide when a treatment is necessary.
Some communities decide to spray when there is a threat of mosquito-transmitted disease, others base their decisions on tourism considerations. Whatever the criteria, it is important to avoid routine spraying that does not take into account the amount of actual mosquito activity and the life cycle of the insect. This results in needless, expensive applications that may result in environmental contamination.
Although mosquitoes can be serious pests, there are several effective means of controlling them in the community and around the house. Mosquito management is most effective when all available control measures are integrated into a community-wide mosquito management program.
Mosquito Management Around the Home
· Eliminate standing water in low spots, ditches, gutters and similar areas.
· Empty weekly or remove receptacles that collect rainwater (bird baths, old tires).
· Mosquito netting and tight screens can provide mosquito-free areas.
· Some mosquitoes are attracted to lights. Reduce unnecessary lighting to make yards less attractive.
· "Bug zappers" do not reduce mosquito landing or biting. They attract and kill many insects but few are mosquitoes that attack humans. Many of the insects killed are beneficial because they feed on garden pests.
· Ultrasonic devices, such as those that claim to mimic dragonflies, do not affect mosquito activity.
· Light-colored clothing is less attractive to adult mosquitoes. Tightly woven fabrics give some protection against biting.
· Deet is considered to be the most effective mosquito repellent. Highly concentrated versions are available but lower (30 to 40 percent) concentrations usually are just as effective and safer for children.
· Citronella and "Avon Skin So Soft" can be used for short periods of relief.
· Some naphthalene products (such as "Mosquito Beater" can be broadcast in yards for temporary relief from adult mosquitoes.
· Adult mosquitoes rest in shrubbery and other shaded areas during the day. These areas can be treated with insecticides such as malathion. Foggers for flying insects can also be used, but will provide only short term relief. Various aerosol insecticides are available for controlling mosquitoes indoors.