Guide To Mosquito Control

Today, many PCOs are interested in breaking into the mosquito control market. What’s involved in performing such work? What species need to be controlled? Find out here.

Perhaps at no other time in the history of our industry has there been a greater opportunity for expanding into mosquito control. In the past two years, these opportunities have increased significantly for two reasons.

In the past, mosquito control typically was performed by state, county and local agencies, which now have fallen on hard times, i.e., lack of money for equipment, materials and personnel. As a result, services have been decreased and, in some cases, totally eliminated. Thus, many residential and commercial operations now are relying on pest management companies to fill this void.

Public concern has been heightened by the threat of such mosquito-borne disease outbreaks as West Nile virus and eastern equine and St. Louis encephalitis (see related story, www.pctonline.com/articles/article.asp?ID=1356&IssueID=138). During the past two summers, West Nile virus drew considerable media attention when crows started dying and several people in the Northeast died as a result of contracting the disease. Many states initiated mosquito abatement programs through contracting.

The principles of mosquito abatement are identical to those typically used for more common structural pests. However, most pest management professionals are not well versed in the identification, biology and habits of mosquitoes. Successful pest management strategies are predicated on this information, so it is essential that companies exploring business opportunities in this area acquire this knowledge.

A comprehensive discussion of mosquitoes can be acquired from several excellent resources, e.g., Mallis Handbook of Pest Control, NPCA Field Guide to Structural Pests and Truman’s Scientific Guide to Pest Control Operations. The purpose of this article, which is more limited in scope, is to outline the principles of mosquito abatement programs.

MOSQUITO BASICS. Mosquitoes are seasonal pests and are typically thought of as tropical and subtropical pests. However, just ask anyone who has lived or visited Alaska in the summer about their mosquito problems and you’ll know this isn’t true.

Most mosquito problems are associated with the annoying bites inflicted by female mosquitoes. They aggravate customers who are having backyard parties, weddings or are relaxing by the pool. Solutions to this kind of problem can be complex and are dependent upon the species of mosquitoes involved and the environment in which they are occurring.

Three mosquito genera are of significant concern within the United States:

• Aedes: Yellow fever mosquito and
Asian tiger mosquito; also transmits
dengue

• Anopheles: Malaria mosquito

• Culex: Southern and Northern house
mosquitoes; transmit West Nile virus
and other encephalitic diseases.

Mosquitoes undergo a complete metamorphosis that has four developmental stages: egg, larva (wiggler), pupa (tumbler) and adult. The first three life cycle stages require water for their development and survival.

The eggs are laid on or near water. Upon hatching, the larvae of most species can be seen wiggling up and down in the water as they feed and return to the surface for air that is taken in through an air tube. After about a week, the larvae mature into pupae that do not feed but tumble in water as they occasionally return to the surface for air. The pupal stage lasts for no more than 1 to 2 days and then the adults emerge.

Males usually are the first to emerge. They remain near the breeding site in order to wait for the females to emerge. Then they mate and soon begin seeking a blood meal. Only the females feed on blood because the mouthparts of male mosquitoes are not equipped for piercing and sucking. Most blood meals are taken at dusk and, less frequently, at dawn. Several of the Aedes species are vicious daytime biters.

Mosquitoes key in on several factors when locating human hosts for blood meals. Light and time of day are critical in attracting mosquitoes to structures. Outdoor lighting and even bright interior lights visible on the exterior can draw mosquitoes from distant locations. Once in the vicinity of humans, CO2 and certain body "odors" become attractants. Unique body chemistry explains why some individuals are bitten more readily than others.

The best method of protecting individuals from mosquito bites is through prevention. Source reduction is the cornerstone of mosquito abatement because without a breeding site, i.e., water, there will be no mosquitoes. The limitation to source reduction is the ability to locate and eliminate bodies of water. This is less problematic for mosquito species that travel less than 100 yards from the breeding site. However, it is much more difficult for species such as salt marsh mosquitoes, which can blow and fly in from more than 20 miles.

Pest management service for mosquitoes runs the gamut from customer education to aerial dispersal of pesticides. Most companies that are involved in this type of service are also involved in customer education, larvaciding and limited adulticiding, while only a select few are involved in aerial operations.

INSPECTION AND IDENTIFICATION. Inspection and identification are the initial steps in all pest management programs. They are extremely critical first steps in mosquito abatement because they provide essential information needed in order to develop the pest management plan. Proper identification provides information on the target species essential for control, e.g., breeding habitats, activity period and flight range. The two primary means of identification (at least to genera) is the collection of adults and larvae. Eggs also can be used but are much harder to recognize in the field. Three primary methods are available to collect specimens for identification:

1. Larval Dipping. Two primary reasons exist for using this technique strategy: collecting larvae for identification and quantifying the number of larvae within a breeding site. The process involves using a long-handled dipper (ladle) to scoop mosquitoes from a breeding site, i.e., body of water. The number of samples is determined by the size of the breeding site. Typically, 5 to 6 samples per acre of surface area is sufficient to determine type and relative number of mosquitoes breeding there. Subsequent sampling can be used to measure the success of larvaciding programs.

2. Light Traps. Light traps are used to collect adult mosquitoes and measure the effectiveness of treatment. The two most widely used traps are the CDC and New Jersey light traps. The CDC light trap is a small portable battery or solar cell operated trap that typically is hung from a tree or permanent structure. The New Jersey trap is considered to be a permanent installation because it is larger and hard wired to a 110-volt power source. Both traps can be outfitted with either a killing jar or a live trap bag (used for collecting specimens for lab pathogen testing).

Light trap efficiency can be enhanced using CO2 in the form of dry ice or from a compressed gas cylinder. Newer traps are in development that use CO2 and another chemical attractant, ocatnol, to enhance trap count and attractiveness of the trap.

Traps typically are operated at least two nights per week; however, the frequency is determined by the contract. Traps are operated only during the "mosquito season," which is determined by geographic location. They should be covered or removed when ultra-low volume adulticides are applied. It is important to understand that not all mosquitoes are attracted to light traps, e.g., daytime biters such as Aedes spp.

3. Landing (Biting) Counts. This technique employs a human as the attractant, i.e., an individual rolls up his/her sleeves and pants legs at dusk and sits in the monitoring location for a specified period of time (from 15 to 30 minutes). The number of mosquitoes that land on the individual’s legs and arms during that time period are counted and translated into mosquitoes per minute. Adult mosquitoes can be collected for identification using a siphoning tube.

PEST MANAGEMENT STRATEGIES. Pest management begins with customer education. Once an identification (at least to genus) is made, basic information about the mosquito problem can be discussed. It is essential that the customer understand the biology of the mosquito, where they may be originating, their role in resolving the problem and depending on the type of mosquito, limitations of potential pest management strategies.

SOURCE REDUCTION (LARVAL ABATEMENT). Eliminating the water eliminates the breeding habitat. Any object that holds water for more than a week is suspect and should be inspected. Some of the more obvious areas around homes and commercial properties include puddles, tree holes, ponds without water circulation, occluded gutters, flower pots, tires, unused equipment, boat covers, small artificial containers and unused swimming pools and hot tubs. In downtown locations, potential locations of water retention and, thus breeding sites, could include storm sewers, electrical and other service pits, air conditioner cooling towers, flat top roofs and blocked drains.

LARVACIDES. Larvacides are chemical and biological agents that kill mosquito larvae when they are applied to bodies of water that cannot be eliminated. Some larvacides can be applied to potential breeding sites that do not contain water at the time of application. When there is sufficient water, the larvacide dissolves to kill the larvae when they hatch.

Larvacides are formulated as liquids, granules (pellets) and briquets (dunks). The type of formulation dictates the longevity, e.g., liquids have the shortest duration and briquets have the longest, depending on conditions. The most common active ingredients for larvaciding are methroprene and B.t.i. These products are dispersed by hand, air and through the use of pressurized or backpack sprayers.

ADULT ABATEMENT. Since most mosquitoes bite at dusk and dawn, they need locations in which to "hang out" during the heat of the day. Some of the more common resting sites include bushes, eaves of buildings, large drain pipes, interiors of structures, high grass and vegetation around structures, unused equipment and dilapidated structures. Resting sites are characterized as shady, damp and protected from the wind.

To the maximum extent possible, resting sites should be eliminated, e.g., grass should be kept short, bushes should be trimmed and open and unused materials should be discarded. Access to interior areas should be denied by the use of screening, air curtains and self-closing doors.

Lighting around and in structures should be changed so that mosquitoes are not attracted to the structure and many of its inherent resting sites and points of entry. The use of yellow bug and sodium vapor bulbs instead of incandescent and mercury vapor bulbs should be encouraged. Lighting should be located away from structures and directed back toward it. Interior lighting is a potential attractant and should be changed as needed.

If resting sites cannot be eliminated, the next course of action is the application of residual, preferably microencapsulated, insecticides to resting sites in order to kill adult mosquitoes when they land on the treated surfaces. Exterior applications typically are made to plants, foundations and around lit entry points. Occasionally interior resting sites, such as entry vestibule walls, undersides of desks, interior plantscapes, etc., require treatment with residual insecticides.

When resting site applications to interior surfaces are not effective in killing adult mosquitoes that enter structures, consideration should be given to the use of light traps. Light traps should be located away from affected personnel and points of entry so that mosquitoes are not attracted into the structure. Light traps are not recommended for outdoor locations because they attract mosquitoes to the areas they are being used to protect.

New products are being introduced that show promise in controlling adult mosquitoes without the use of insecticides. One system uses heat and CO2 to mimic humans and animals and lure mosquitoes to their electrocution. A similar device adds octanol, a strong mosquito attractant, to the mix.

The use of aerosols either indoors or outdoors to kill adult mosquitoes is transient and kills only the mosquitoes present or contacted at application time. There are no residual effects of aerosols so mosquitoes that subsequently fly into the area will be unaffected by the treatment.

Every effort should be made to avoid interior aerosol applications to control adult mosquitoes. If this is necessary, applications should be made only when all personnel are out of the area and ventilation systems have been turned off. Reentry should be denied for at least two hours following treatment or as otherwise directed by the label.

Outdoor applications of adulticides typically involve the use of either backpack or vehicular-mounted ULV dispersal equipment. This equipment should be calibrated to deliver a droplet size in accordance with the product label. Applications should not be made when the wind speed exceeds 10 mph, when it is raining or when the air temperature at the ground level is warmer than the temperature six feet above the ground.

In situations in which individuals cannot be protected by the aforementioned strategies, the best option is to use repellents. Three types of repellents are recognized: area, skin and clothing. Area repellents include products such as citronella and a new thermal device that employs d-cis/trans allethrin. The heated active ingredient is capable of repelling mosquitoes outdoors within a 15-foot diameter.

Most research has demonstrated that DEET is the best skin repellent. It is not necessary to use concentrations greater than 33 percent. Clothing repellents containing permethrin are very effective in repelling mosquitoes, even after treated clothing is washed five times.

CONCLUSION. Mosquito abatement is a product that can easily be marketed by our industry. Most companies can expand into this business with little capital investment. Most of the services described previously are analogous to perimeter pest management operations that are readily performed already by most pest management professionals. There is no better time than the future to expand your role as a protector of health.

MORE MOSQUITO INFORMATION

Dr. David Dame, president of the American Mosquito Control Association, and Tom Fasulo, an extension entomologist at the University of Florida, recently produced a new National Public Health Pest Control manual for the United States Department of Agriculture. The manual includes a chapter on mosquitoes (written by Dame), which is on the Web at www.ifas.ufl.edu/~pest/vector. Also at the site are two free downloadable tutorials on mosquitoes, based on the chapter. Visit the site today!

For More Information:

For more about this market, stop by this feature at www.pctonline.comThere we have information you can give your customers so they can help you with mosquito control.

Also on our site, we have information about mosquito control programs from Wellmark International and Aventis Environmental Science.

The author is technical director of American Pest Management, Takoma Park, Md. He can be reached at 301/891-2600 or rkramer@pctonline.com