Cluster Flies Treatment

Reasons for control

Cluster flies are not damaging to property when they enter buildings in the autumn purely to hibernate over the cold winter months. As mentioned above they feed on decaying vegetation and earthworms. Cluster flies are not to be associated with dead animal bodies, faeces and the resulting maggots. Fibre glass insulation material in lofts can look unsightly if covered with the bodies of flies that have not hibernated successfully although its insulation properties will not be altered and no damage to the roof structure will occur.

If the loft is home to a hibernating colony of flies, first floor lighting diffusers or sunken spotlight lenses can become full of dead or dying flies. This often occurs in houses where the loft area has been converted into a living room. In most buildings built after 1950, the external roof covering has an under felt layer. Cluster flies can successfully hibernate undetected between these two layers. Often cluster flies can be seen basking on sunny grassland or resting on south facing walls of buildings. Cluster flies, like birds, return to roof spaces previously occupied so re-infestation is almost inevitable.

Control/Treatment

The only option available is to control the number of flies by either:-
Insecticidal space spray (N.B. if bats are present in your loft/attic this will not be possible). Number of visits required will depend on the time of year the treatment is carried out and also on weather conditions (mild autumn) as to when flies migrate in to hibernate.