Mosquito control

Mosquito control is the task of managing the population of mosquitoes to reduce their damage to human health, economies, and enjoyment of mosquito-ridden areas. Mosquito control is a vital public-health practice throughout the world and especially in the tropics because mosquitos spread many diseases, such as malaria.

Mosquito-control operations are targeted against three different mosquito problems:

Nuisance mosquitoes bother people around homes or in parks and recreational areas;
Economically important mosquitoes reduce real estate values, adversely affect tourism and related business interests, or negatively impact livestock or poultry production;
Public health is the focus when mosquitoes are vectors, or transmitters, of infectious disease agents.

Disease organisms transmitted by mosquitoes include West Nile virus, Saint Louis encephalitis virus, Eastern Equine Encephalomyelitis virus, Everglades virus, Highlands J virus, La Crosse encephalitis virus in the United States; dengue fever, yellow fever, Ilheus virus, and malaria in the American tropics; Rift Valley fever, Wuchereria bancrofti, Japanese Encephalitis, dengue fever, yellow fever, and malaria in Africa and Asia; and Murray Valley encephalitis in Australia.

In the United States, states with sizeable mosquito-control programs include California, Florida, New Jersey, Louisiana, Minnesota, Michigan, North Dakota, and Texas, among others.

Modern mosquito-control methods

Long-range, intelligent, ecologically valid, and environmentally sound pest control must be approached by use of all available control methods. This is known as integrated pest management (IPM). Typical mosquito-control programs using IPM first conduct larval and adult surveys, in order to determine the species composition, relative abundance, and seasonal distribution of adult and larval mosquitoes, and only then are the best and most effective methods of control utilized.

General methods

Depending on the situation, source reduction, larviciding (control of larvae), or adulticiding (control of adults) may be used to manage mosquito populations. These techniques are accomplished using habitat modification, pesticides, biological-control agents, and trapping.

Monitoring mosquito populations

Adult mosquito populations may be monitored via landing rate counts, or mechanical traps. For landing rate counts, an inspector visits a set number of sites every day, counting the number of adult female mosquitoes that land on a part of the body, such as an arm or both legs, within a given time interval. Mechanical traps use a fan to blow adult mosquitoes into a collection bag that is taken back to the laboratory for analysis of catch. The mechanical traps use either light, carbon dioxide, or a combination of both, to lure adult female mosquitoes into the trap.

Monitoring larval mosquito populations involves collection of larvae with a half-pint dipper or a turkey baster. The habitat, approximate total number of larvae and pupae, and species identity are noted for each larval collection.

Source reduction

Source reduction can be as simple as emptying water from containers around the home. This is something that homeowners can accomplish without much difficulty. Other techniques used on large scale have included open water marsh management, rotational impoundment management, ditching, and improved management of stormwater and wastewater.

Open water marsh management (OWMM) involves the use of shallow ditches, about 4 feet wide and 2 feet deep, to create a network of water flow within marshes and to connect the marsh to a pond or canal. The network of ditches allows the mosquito habitats to drain and also allows fish into mosquito habitats, where they will feed on mosquito larvae and reduce the need for other control methods, such as pesticides. Open-water marsh management is used on both the eastern and western coasts of the United States.

Rotational impoundment management (RIM) involves the use of large pumps and culverts with gates to control the water level within an impounded marsh. RIM allows mosquito control to occur while still permitting the marsh to function in a state as close to its natural condition as possible. Water is pumped into the marsh in the late spring and summer to prevent the female mosquito from laying her eggs on the soil. The marsh is allowed to drain in the fall, winter, and early spring. Gates in the culverts are used to permit fish, crustaceans, and other marsh organisms to enter and exit the marsh. RIM allows the mosquito-control goals to be met while at the same time reducing the need for pesticide use within the marsh. Rotational impoundment management is used to a great extent on the east coast of Florida.

Larviciding

Control of larvae can be accomplished through use of contact poisons, growth regulators, surface films, stomach poisons (including bacterial agents), and biological agents such as fungi, nematodes, copepods, and fish.

Adulticiding

Control of adult mosquitoes is the most familiar aspect of mosquito control to most of the public. It is accomplished by ground-based applications or via aerial application of chemical pesticides. Generally modern mosquito-control programs in developed countries use low-volume applications of pesticides, although some programs may still use thermal fogging. DDT was formerly used throughout the world for large area mosquito control, but it is now banned in most developed countries. Controversially, DDT remains in common use in many developing countries, which claim that the public-health cost of switching to other control methods would exceed the harm caused by using DDT.

References

Florida Coordinating Council on Mosquito Control. 1998. Florida Mosquito Control: The State of the Mission as Defined by Mosquito Controllers, Regulators, and Environmental Managers. University of Florida.

Mullen, G. and L. Durden. 2002. Medical and Veterinary Entomology. Elsevier Science.

Service, M.W. 1993. Mosquito Ecology: Field Sampling Methods. Elsevier Applied Science.

Ware, G.W. 1994. The Pesticide Book. University of Arizona.