Fly Treatment

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Good sanitation is the basic step in all fly management. Whenever possible, food and materials on which the flies can lay their eggs must be removed, destroyed as a breeding medium, or isolated from the egg-laying adult. Killing adult flies will reduce any infestation, but elimination of breeding areas is necessary for good management.

House flies and many flesh flies, bottle flies and blow flies breed in similar substances, such as decaying organic materials, garbage, animal excrement or polluted ground. Removal of these materials from the vicinity of infested premises will frequently make other measures unnecessary.

Recommending twice-weekly garbage removal depends on timing. The final larval instar leaves the larval food medium and wanders for considerable distances prior to pupation; so it is the length of time from egg laying to the molt of the last larval instar that is important and that necessitates twice-weekly pickups.

Other considerations in sanitation include regular removal of livestock or pet manures, soiled bedding, straw and all other decaying plant and animal matter. Garbage cans, recycling receptacles and dumpsters should have tight-fitting lids and be cleaned regularly. Dry garbage and trash should be placed in plastic garbage bags. Wet garbage should first be wrapped in old newspaper and then put in plastic garbage bags. All garbage receptacles should be located as far from doors as possible.

Any sanitation program in fly management must be tailored to fit each specific situation.

Basically, fly management should include any step that will help to eliminate or prevent the establishment of any medium in which fly larvae will develop or that will be attractive to adult flies. 

Don’t overlook the importance of moisture in fly breeding media; simple drainage will often aid control.

Although it may not always be feasible to practice all the sanitary measures that would contribute to fly management, simple and practical sanitation will often make the difference between satisfactory and unsatisfactory fly levels. Sometimes, significant results can be obtained through sanitation alone.

Openings to buildings should be tightly screened with screen having a mesh no larger than 12 to the inch for the larger flies and 18 to the inch for smaller insects. Eighteen-mesh screening is required to exclude mosquitoes, but this reduces the amount of light and air that can pass through. Screen doors should open outward. For extreme infestations, a double set of doors may be of value. It is usually unnecessary to screen above the third story of a building.

Doors that must open for customers, trucks or passage of freight may permit entry of flies. Where such doors are opened constantly, an airstream (air curtain or door) may be used to prevent fly entry. An airstream must have a velocity of at least 1,600 ft. per minute to be effective. Equipment must be designed for each individual installation.

Fly traps or flypaper may also be useful in some management situations. They require a sticky surface and may contain a material attractive to flies. They may trap large numbers of flies, but are most effective when used to supplement other management techniques. Their use in spots outside the limits of an area to be protected, however, may be of some value, as they undoubtedly reduce fly populations. Their use is usually limited to areas where aesthetics are not of primary importance.

Electrically charged screens and insect light traps (ILTs) are also available, but can be used effectively only in certain areas. They should be used to supplement other management techniques. The number of ILTs used in buildings (such as food-handling establishments) and their placement are critical factors in successfully using them in fly management. 

Pest management professionals are most frequently called on to control adult flies. Where breeding areas cannot be eliminated or treated, control of adults may be the only practical measure.

Residual insecticide sprays are still generally effective for fly control outdoors, but localized resistant populations may be a problem with some of these insecticides. Adulticides include some of the pyrethroids, as well as boric acid and other insecticides labeled for fly management.

Wettable powder, soluble concentrate or microencapsulated formulations usually provide the best residual activity. These are applied most effectively as coarse, wet sprays to outdoor surfaces on which flies prefer to rest, such as porches, garbage cans, dumpsters, garages, doghouses or kennels, vegetation and similar areas. Sun-exposed surfaces on outside walls are given special attention.

Pets should be removed from the area before spraying and not allowed to return until the spray has dried. Insecticide baits are available for outdoor use and kill flies rapidly, but their effectiveness is short-lived unless treatments are repeated. Baits are best used to supplement a spray program. Wet baits can be sprayed or sprinkled on fly resting surfaces outside the home. Dry baits can be scattered around garbage cans or placed in garage windows or near other fly resting surfaces. Fly baits can be purchased in ready-to-use forms.

Temporary control of flies can be obtained indoors by the use of contact sprays. These applications give quick knockdown and kill of flies but have no lasting effect. They can be applied with fogging or ultra-low volume (ULV) aerosol equipment. Before making such an application, completely cover food, food-handling equipment and utensils to avoid contamination.

Lime-release aerosols (“bug bombs”) are commonly used for fly control but are effective only when used in enclosed rooms where air circulation is limited. The public’s exposure to insecticide should be considered carefully when using these aerosols.

Space sprays, residual sprays or ULV aerosols may be useful outdoors. Applied over an area as a fog, mist, aerosol or wet spray, these insecticides may be of value in reducing adult fly populations.

Fly larvae may be controlled in breeding media by the application of insecticides to the media. This method should be considered only when sanitation cannot do the job because beneficial predators and parasites are often susceptible to common larvicides. Fly populations may increase when the insecticide has lost its residue, and natural control organisms do not return as rapidly as the flies do.