Management
The more commonly used control measures for house flies are sanitation, use of traps, and insecticides, but in some instances integrated fly control has been implemented. The use of biological control in fly management is still at a relatively early stage.
Sanitation or cultural control. Good sanitation is the basic step in any fly management program. Food and materials on which the flies can lay eggs must be removed, destroyed as a breeding medium, or isolated from the egg-laying adult. Since the house fly can complete its life cycle in as little as seven days, removal of wet manure at least twice a week is necessary to break the breeding cycle. Wet straw should not be allowed to pile up in or near buildings. Since straw is one of the best fly breeding materials, it is not recommended as bedding. Spilled feed should not be allowed to accumulate but should be cleaned up two times a week. Ordinarily, fly control from 1 to 2 km around a municipality prevents prevents house fly infestations.
Killing adult flies may reduce the infestation, but elimination of breeding areas is necessary for good management. Garbage cans and dumpsters should have tight-fitting lids and be cleaned regularly. Dry garbage and trash should be placed in plastic garbage bags and sealed up. All garbage receptacles should be located as far from building entrances as possible.
For control at waste disposal sites, refuse should be deposited onto the same area as inorganic wastes to deteriorate the capacity of breeding resources, or the disposed refuse should be covered with soil or other inorganic wastes (15 cm thickness) on every weekend or every other weekend.
Around homes and businesses, screening or covering of windows, doors or air doors, and trash containers proves useful in denying access of flies to breeding sites. Packaging household trash in plastic bags, and burying trash under at least 15 cm of soil and in sanitary landfills also helps to eliminate breeding. Trash cans and dumpsters should have tight-fitting lids; failing this, slow release fumigant insecticide dispensers are sometimes installed on the inside of the lids to reduce fly survival.
In agricultural areas, manure can be scattered over fields so that it quickly dries and becomes unsuitable for egg and larval survival. Composting of manure can be effective if the compost is properly maintained, including regular turning. Manure can also be liquefied and stored in lagoons anaerobically, though at some point the solids need to be separated.
Traps. Fly traps may be useful in some fly control programs if enough traps are used, if they are placed correctly, and if they are used both indoors and outdoors. House flies are attracted to white surfaces and to baits that give off odors. Indoors, ultraviolet light traps collect the flies inside an inverted cone or kill them with an electrocuting grid. One trap should be placed for every 30 feet of wall inside buildings, but not placed over or within five feet of food preparation areas. Recommended placement areas outdoors include near building entrances, in alleyways, beneath trees, and around animal sleeping areas and manure piles. Openings to buildings should be tightly screened with standard window screen, thereby denying entrance to flies.
Traps can be baited with molasses, sugar, fruit or meat, and often are used in combination with a device that captures the attracted flies. The sex pheromone (Z)-9-tricosene also functions as an aggregation pheromone, and is called muscalure. Muscalure is formulated with sugar as a commercially-available fly bait for local population suppression, as well as an enhancement for population monitoring.
Ultraviolet light traps can be used to assess population levels, but also serve as a non-chemical control technique that can be used indoors in both agricultural and non-agricultural areas. They normally function by electrocuting flies that enter the trap, though those used in restaurants typically have a sticky panel. Flies do not orient to traps from a great distance, so several are normally needed for them to be effective. Placement should include within 4 to 8 m of entryways, and within 1.5 m of the floor, to take advantage of fly flight behavior. They should be operated continuously, although they are most effective when the room lights are off.
Biological control. With the increasing incidence of insecticide resistant house fly populations, rising costs of insecticides and a growing public concern about actual or potential problems associated with insecticides, interest in alternative house fly control strategies has increased.
Natural biological suppression of the house fly results primarily from the actions of certain chalcidoid wasps (Hymenoptera: Pteromalidae), of which many species have been associated with house fly around the world. Among the more important are Muscidifurax and Sphalangia spp. Ichneumonids and other parasitoids, as well as some predatory insects (especially histerids [Coleoptera: Histeridae] and staphylinids [Coleoptera: Staphylinidae]), also contribute to fly mortality, but under optimal fly breeding conditions the house fly quickly builds to high numbers. The more important in poultry facilities are the wasps M. raptor and S. cameroni. Leaving a layer of old manure in the pits when manure is removed might enhance or stabilize the suppression of the house flies densities by parasitoids and predators.
Augmentative biological control (Periodic release of parasitoids during winter and spring, and following manure removal) using insectary-reared parasitoids has been quite successful in some dairies, feedlots and poultry house situations. The species most often released for biological suppression in North America are M. raptor, M. raptorellus, S. endius, and S. nigroaenea. These different species function better under different conditions, some performing better under cooler or warmer conditions, others parasitizing flies near the surface or deeper in the pupation medium.
The larva of the black dump fly, Hydrotaea (=Ophyra) aenescens, is also regaining popularity as a biological control agent for controlling house flies on poultry farms without the use of pesticides. The adult black dump fly is similiar in appearance to the adult house fly (Hogsette and Jacobs 2003).
Integrated fly control. Integrated fly control programs for caged-poultry houses are based on the following strategy:
- selective applications of insecticides against the adult,
- start insecticide control measures early in the spring before flies appear and repeat as frequently as needed through the warm months, and
- the manure is left undisturbed throughout the warm months when fly breeding may occur. The manure should be removed once very early in the spring before any flies appear.
Chemical control. When the house fly is a mayor pest in commercial egg production facilities, the control of this insect is by the application of adulticides, or larvicides to directly or indirectly suppress adult densities. Residual wall sprays can be applied where the flies congregate. Resistance to permethrin develops more rapidly in fly populations from farms on a continuous permethrin regime than in farms in which permethrin and diclorvos have been alternated.
Outdoors, the control of flies includes the use of boric acid in the bottom of dumpsters, treatment of vertical walls adjacent to dumpsters and other breeding sites with microencapsulated or wettable powder formulation, and the use of fly baits near adult feeding sources.
