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Cluster fly treatment

Cluster fly treatment

When making a booking for cluster fly treatment you are authorising Stroud District Council to carry out the treatment and/or destruction of pests on the above premises. Please let us know well in advance if you are unable to keep your appointment. If you fail to keep an appointment or give less than one working days’ notice you may be charged for the full cost of the treatment.

Cluster flies are found throughout the UK and their common name refers to their habit of forming clusters when “hibernating” - in often large numbers – in buildings. Whilst there is a specific species of common cluster fly (Pollenia rudis), there are other species of cluster fly and swarming flies which have a similar hibernating nature and these may also be involved in forming mixed populations of flies inside suitable buildings.

The life cycle of the Cluster Fly is very much dependent on the prevailing weather conditions, and in this country, two generations a year are usual, but in hot summers, up to four generations per year are possible. Cluster flies are “field” flies and in summer and early autumn they are of no consequence. However, as the weather becomes cooler, they seek out shelter in nooks and crannies in houses and other buildings. As the weather becomes colder, they search for more protection from the elements and may be seen in large numbers, particularly in roof spaces, lofts, etc., sometimes with several thousand flies clustered together.

The Council’s pest Control Officers will treat areas affected by cluster flies with a smoke generator or ULV Fogger (a piece of equipment designed to disperse pesticide chemicals in the air as a mist or fog).

What to do before a treatment takes place

  • If there is evidence of Bats in the area to be treated, no treatment will take place.
  • Remove any plant or aquatic animals from the area to be treated.
  • Make sure there is adequate access to the fly infested areas and that loft hatches and any loft ladders can be safely used.
  • The treatment will only kill the flies that are in the area at the time.

Safety advice

  • Do not enter the treated area for a minimum of 3 hours.
  • In case of accidental contact with insecticide:-
    • Wash off skin immediately, remove contaminated clothing
    • Eyes – rinse at least 15 minutes, seek medical advice
    • Inhalation – more than incidental move to fresh air, keep warm, blow nose and seek medical advice

If you would like further advice or information please contact the Environmental Health Service on

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