There are four main groups of flies that may cause issues;
- House flies and Bluebottle flies
- Fruit flies
- Sewer or drain flies
- Cluster flies
House flies and Blue bottle flies
Everybody experiences flies in their homes at some time or another. Although they do have the potential to spread germs and diseases, there should be no problems encountered if good hygiene standards are maintained and foodstuffs are not freely available to them.
It is only when they appear in large numbers that they can become cause for concern, and this is usually the case for one of two reasons: Either there is infested food matter somewhere nearby, or there is the carcass of a dead animal in which the flies have laid their eggs.
Control
The main method of control is to find and remove the cause of the problem- Infested food should be quite easy to find and remove. A dead animal how ever cannot always be found. Good places to check are lofts (for birds, squirrels etc), behind old fireplaces, under floor boards and behind bath panels, kitchen appliances and cupboards.
Whether the cause is found or not, the use of insecticides is recommended. A flying insect spray can be used to treat the affected room generally. For areas where the cause is found, a powder or a crawling insect spray can be used. Other means of treatment include traps, which can be hung up, solid block insecticides in plastic vented containers and ultra violet electric killers.
Fruit flies
These flies are not very common in the home but where they do occur, it is usually due to fermenting fruit or old vegetables attracting them. They are a problem because they also feed on faeces etc. before landing on clean surfaces & foodstuffs.
Control
This can be achieved by removing the foods attracting them .
The use of insecticides is recommended. A flying insect spray can be used to treat the affected room generally. For areas where the cause is found, a powder or a crawling insect spray can be used. Other means of treatment include traps, which can be hung up, solid block insecticides in plastic vented containers and ultra violet electric killers.
Sewer or drain flies
These, as the name suggests, are closely associated with water. They lay their eggs in the sludge left as water evaporates. In the summer, infestations can occur in areas such as puddles on flat roofs and blocked outlet drains or gutters, and from these areas the flies can migrate indoors.
If the infestation is only indoors, sources of standing water should be checked (i.e. plant pots). Be aware that a 'pool' of water is not even necessary for these flies to successfully lay eggs. Something as small as a little trickle of water from a pipe joint (for example when the toilet is flushed) can cause this problem, therefore all plumbing should be inspected.
Control
This can be achieved by denying the flies their source of water.
The use of insecticides is recommended. A flying insect spray can be used to treat the affected room generally. For areas where the cause is found, a powder or a crawling insect spray can be used. Other means of treatment include traps, which can be hung up, solid block insecticides in plastic vented containers and ultra violet electric killers.
Cluster flies
The cluster fly is approximately 8mm long and recognised by its abdominal patterns and dark grey/olive thorax with dense yellow matted hairs. The adults are frequently mistaken for the housefly, although they are somewhat darker and larger and fold one wing over the other when at rest. They are also much more sluggish in their movements and fly much slower.
Habitat
Found mainly throughout Europe and the UK. The common name refers to its habit of clustering and hibernating in numbers inside buildings.
Importance
During the summer and early autumn, these flies are of no consequence. As the season cools, they seek shelter in nooks and crannies in buildings. As temperatures drop they search for more protection and frequently form vast clustering masses in roof spaces and lofts, with several thousand flies clustered together. It has often been observed that a single house or building in a row of similar buildings will be chosen year after year for this clustering phenomenon.
Some large aggregations of flies do produce a rather sickly smell and, if warmed up accidentally or artificially during their hibernation, may emerge rather lazily and create some concern amongst the people using the building. This has occurred commonly in places such as church halls and domestic bedrooms. They are of no particular harm but are a nuisance because of their great numbers.
Life cycle
The adult female lays eggs loosely on and around damp soil, beneath dead and rotting leaves, etc. After about a week the larvae hatch from the eggs and actively seek earthworms to which they cling and then bore through the body wall. The conventionally shaped fly maggots develop inside the earthworm.
Mature larval stages have been observed to push their hind ends back through the earthworm's body wall to allow their breathing spiracles to gain access to the free air. At or near to the death of the earthworm, the larva bores its way out again and pupates in the soil. Since this a free-living 'field' insect, the life cycle is very dependent of weather conditions. In Britain it seems that two generations per year are common, but in hot summers up to four generations per year might be possible.
Control
There has not been a lot of research on the control methods for cluster and swarming flies and they are often ineffective or at best, incomplete. It is often not possible to keep flies from entering premises and control of the flies outdoors in their breeding areas is considerable and impractical.
It is recommended that a combination of physical and chemical control methods are used and it should be stressed that using silicone or other suitable exterior sealing compound around window frames and blocking other obvious entry points can contribute greatly to control. It is difficult to use insecticide in and around unsealable entry points to some buildings, (e.g. thatched roofs, or under tiles or slates) but in some cases where recurrent problems have been experienced, prophylactic dusting of access points can be partly effective.
Once the flies are inside, e.g. in the loft or attic space, control is relatively simple both with physical methods and a range of insecticides and formulations. Occasionally a vacuum cleaner (nozzle type) can be used as the sole control method where aggregations exist within reach and the collected flies can be disposed of in a sealed bag. Alternatively, or in addition, most pyrethrum and pyrethoid based space sprays will quickly kill exposed flies and in some situations, smoke formulations based on permethrin can be very effective.
Proofing of buildings
- Fill in any holes around pipes and cables where services, (gas, water, electricity) enter the house, using cement/mortar or other suitable external filling compound.
- Fill in any holes around overflows, sink waste pipes, soil pipes and chimneys, etc., with cement/mortar or other suitable external filling compound.
- Fill in gaps/holes where roof tiles meet the soffit boards. Use crumpled wire mesh then fill in with cement or other suitable external filling compound.
- Re-point loose/missing mortar in brickwork.
- Seal outside windows and doorframes with mastic. Seal inside windows and doorframes with general purpose household sealer.
- Cover air vents or airbricks with fine zinc gauze, fixed securely.
