Mosquito control

Control

Mosquito control can be divided into two areas of responsibility: individual and public. Most often it's performed following the Integrated Mosquito Management (IMM) concept. IMM is based on ecological, economic and social criteria and integrates multidisciplinary methodologies into pest management strategies that are practical and effective to protect public health and the environment and improve the quality of life. IMM strategies are employed in concert with insecticide. These include source reduction, which incorporates physical control (digging ditches and ponds in the target marsh) and biological control [placing live mosquito fish (Gambusia) in the ditches and ponds to eat mosquito larvae]. Other non-chemical control methods include invertebrate predators, parasites and diseases to control mosquito larvae. Adult mosquito biological control by means of birds, bats, dragonflies and frogs has been employed by various agencies. However, supportive data is anecdotal and there is no documented study to show that bats, purple martins, or other predators consume enough adult mosquitoes to be effective control agents.

Pesticides may be applied to control larvae (larvicides) or adults (adulticides). Applications of adulticides or larvicides are made after the presence of mosquitoes has been demonstrated by surveillance procedures. Application is made by prescribed standards. All insecticides must have the name and amount of active ingredient (AI) appearing on the label; examples are DEET and pyrethroids. Check the label before buying. No pesticide is 100 percent safe and care must be exercised in the use of any pesticide. Material Safety Data Sheets (MSDS) contain basic information about a product intended to help you work safely with the material.

Larval Control

An efficient way to control mosquitoes is to find and eliminate their larval habitat .Eliminating large larval development sites (source reduction) such as swamps or sluggishly moving streams or ditches may require community-wide effort. This is usually a task for your organized mosquito control program. They might impound an area of water, establish ditches or canals or control the aquatic weeds (cattails, water lettuce, etc) on a body of water. The second method used by organized mosquito control agencies is larviciding. This utilizes the application of insecticides targeted at the immature mosquitoes - the larvae or pupae. These are applied to bodies of water harboring the larvae. However, since larvae do not usually occupy the entire body of water, larvicides are applied where the larvae are, usually the areas near the shoreline of the lake, stream or ditch. Larvicides differ from adulticides in that they are directed at a limited targeted area, i.e. the body of water and often only that area where the larvae grow and mature. Larvicides are classed as stomach toxins, contact larvicides, surface agents, natural agents and insect growth regulators (IGR). Some examples are listed in the Homeowner section that follows.

Homeowners can take the following steps to prevent mosquito breeding on their own property:

1. Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water. Do not allow water to accumulate in the saucers of flowerpots, cemetery urns or in pet dishes for more than 2 days.
2. Clean debris from rain gutters and remove any standing water under or around structures, or on flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles that remain for several days.
3. Change the water in birdbaths and wading pools at least once a week and stock ornamental pools with top feeding predacious minnows. Known as mosquito fish, these minnows are about 1 - 1-1/2 inches in length and can be purchased or native fish can be seined from streams and creeks locally. Ornamental pools may be treated with biorational larvicides [Bacillus thuringiensis subsp. israelensis (Bti) or S-methoprene (IGR) containing products] under certain circumstances. Commercial products "Mosquito Dunks" and "Mosquito Bits" containing Bti can be purchased at many hardware/garden stores for homeowner use. Wellmark International, a division of Central Life Sciences, has developed Pre-Strike Mosquito Torpedo that kills developing mosquitoes using insect growth regulator (IGR) technology. Like Mosquito Dunks, Pre-Strike can be found at many home/garden and pet specialty stores.
4. Fill or drain puddles, ditches and swampy areas, and either remove, drain or fill tree holes and stumps with mortar. These areas may be treated with Bti or methoprene products also.
5. Eliminate seepage from cisterns, cesspools, and septic tanks.
6. Eliminate standing water around animal watering troughs. Flush livestock water troughs twice a week.
7. Check for trapped water in plastic or canvas tarps used to cover boats, pools, etc. Arrange the tarp to drain the water.
8.  Check around construction sites or do-it-yourself improvements to ensure that proper backfilling and grading prevent drainage problems.
9.  Irrigate lawns and gardens carefully to prevent water from standing for several days.
10. If ditches do not flow and contain stagnant water for one week or longer, they can produce large numbers of mosquitoes. Report such conditions to a Mosquito Control or Public Health Office. Do not attempt to clear these ditches because they may be protected by wetland regulations.

Recently another method of larval control has become available. The LarvaSonic is an acoustic larvicide system. Sound energy transmitted into water at the resonant frequency of the mosquito larvae air bladders instantly ruptures the internal tissue and causes death.

More information on adulticides, larvicides, MSDS's and the equipment used to disperse these mosquitocides may be found on the "links" section of this web site.

Adult Control

Mosquito Traps. Insect electrocutors (bug zappers) and mosquito trapping devices are 20th century control measures. Manufacturers modernized 19th century mosquito trapping devices such as the New Jersey light trap with more "bells and whistles" to improve their appeal to the public. Insect electrocuter light traps have been extensively marketed for the past several years claiming they can provide relief from the biting mosquitoes and other pests in your back yard. Numerous devices are available for purchase that claim to attract, repel or kill outdoor infestations of mosquitoes. They should be thoroughly researched before being purchased.

Other mosquito traps are designed to mimic a potential mammalian host (horse, cattle, man and domestic pets) by emitting a plume of carbon dioxide, heat and moisture, which is often combined with an additional attractant, i.e., octenol, to create an attractant to mosquitoes, no-see-ums, biting midges and black flies. After drawing the insects to the trap, a vacuum device sucks the insects into a net or cylinder where they dehydrate and die. No electric killing grid or pesticides are used.

Scientific data relative to the effectiveness of these devices is sparse so be sure to review all the information available before purchasing one. In addition, some of the mosquito traps are quite expensive. For more information see the page on mosquito traps.

Space sprays. Mosquitoes used to be killed inside the house by using a flit gun. Household aerosol space sprays containing synergized pyrethrum or synthetic pyrethroids (allethrin, resmethrin, etc.) are available now. The major advantage of space treatment is immediate knockdown, quick application, and relatively small amounts of materials required for treatment. Space sprays are most effective indoors. Outdoors, the insecticide particles disperse rapidly and may not kill many mosquitoes. The major disadvantage of space spraying is that it will not manage insects for long periods of time.

Only insecticides labeled for flying insect management should be sprayed into the air. Best results are obtained if doors and windows are kept closed during spraying and for 5-10 minutes after spraying. Always follow directions on the label.

Outdoor Control. Homeowners, ranchers or businesses may use hand-held ULV foggers, portable or fogging attachments for tractors or lawn mowers for temporary relief from flying mosquitoes. Pyrethrins or 5% malathion can be fogged outdoors. Follow instructions on both the insecticide label and fogging attachments for application procedure.

Mechanical Barriers. Mosquitoes can be kept out of the home by keeping windows, doors and porches tightly screened (16-18 mesh). Those insects that do get into structures can be eliminated with a fly swatter or an aerosol space spray containing synergized pyrethrum.

Vegetation Management. Adult mosquitoes prefer to rest on weeds and other vegetation. Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds adjacent to the house foundation and in their yards, and mowing the lawn regularly. To further reduce adult mosquitoes harboring in vegetation, insecticides may be applied to the lower limbs of shade trees, shrubs and other vegetation. Products containing synthetic pyrethroids such as deltamethrin and lambda-cyhalothrin have proven effective. Paying particular attention to shaded areas, apply the insecticides as coarse sprays onto vegetation, walls and other potential mosquito resting areas using a compressed air sprayer. Always read and follow label directions before using any pesticide.

Many of the mosquito problems that trouble homeowners and the general population cannot be eliminated through individual efforts, but instead, must be managed through an organized effort. Many states have some sort of organized mosquito control, either at the State, County or city level. There are approximately 734 organized mosquito control organizations that specialize in area mosquito control. Upwards of 1105 residential communities have organized to control their mosquito problems. There has been an increase in the number of these organizations in the United States since the West Nile arbovirus outbreak in 1999. These organized management programs incorporate the IMM strategies mentioned above which include permanent and temporary measures. Permanent measures include impounding water and ditching, and draining swampy mosquito breeding areas. Temporary measures include treating breeding areas to kill larvae and aerosol spraying (ULV) by ground or aerial equipment to kill adult and larval mosquitoes. If you live within an organized mosquito management district, support it in its control efforts. Organized mosquito management can accomplish much more than individual efforts. If you are not sure about whether your community has a mosquito control district, contact the local division of health officials.

Aerial adult mosquito control using fixed-wing aircraft or helicopters and/or ground adult mosquito control using truck or boat mounted equipment are often the most visual aspects of an organized mosquito control program. This method of control is called adulticiding. Although it is often expensive in terms of manpower, equipment and inventory, sometimes difficult to accomplish and more likely to affect non-target organisms if mishandled, it is the only method to rapidly reduce infected mosquito numbers or to control pest and nuisance mosquitoes from inaccessible breeding areas that are interfering with normal outdoor activities of a community.