Cluster Fly Case Study – October 2023

As with most pests, in some years conditions are just right for populations to explode – and 2023 has truly been one of these for cluster flies. We have seen terrible infestations, much greater than ever before.

Luckily, they are relatively easy to treat, and it is just the scale of the problem this year which is challenging.

This case study relates to a substantial stately home we treated recently. By far the largest cluster fly infestation we have ever been called to in a “domestic” setting, but completely manageable if approached correctly and methodically.

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The Starting Point - Full Fly Survey

The starting point is a full in-depth survey, conducted by our head of technical operations Carl Hoult, to establish the extent of the problem and whether there are any underlying causes. Carl has the benefit of over 12 years of experience and is one of the most qualified pest control technicians in the UK.

The survey covered all the impacted room, including the loft and roof spaces.

We concluded that the fly problem hasn’t originated from any disturbance in the roof but is much more likely due to the very mild winters we have experienced. This has caused a much larger base population of “hibernating” flies to survive the warm winters, and we have seen some Norfolk villages overrun with lesser houseflies and similar species.

The treatment plan itself was relatively straightforward, only complicated by the sheer scale of the problem and property.

The work required our technicians to use a permethrin based fogging agent to fog all appropriate areas of the property.

The three technicians involved, wore full PPE including full face masks for protection.

Abate Cluster Fly Case Study

The Treatment Process: Step 1 - Fogging

The treatment had what we call “instant knockdown” in which the target species does not survive contact with the product, as the effect of the insecticide is near instant (very similar to domestic fly spray in its action).

Similar to standard fly spray, the fogging agent dissipated in a small amount of time making it ideal for safety.

This eradicated the vast majority of cluster flies within the first two days.

The main reason for any to survive this treatment is either they were outside of the building when the treatment was carried out, or were hidden in wall voids/cracks & crevices and therefore protected from the insecticide. Hence a second treatment was planned a week later, to destroy any flies not disposed of in the first round of treatment.

All water tanks and fire alarms were protected from the fogging agent with the fire alarms switched off during the treatment.

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The Treatment Process: Step 2 - Insecticidal Oil

On the ground floor we didn’t use our fogger due to the number of precious artefacts and furniture present, using dust sheets and plastics to protect the flooring as an additional precaution.

We manually applied a permethrin and tetramethrin oil based insecticide to all low level windows as an added measure to ensure sustained knock down.

This insecticidal oil does not dissipate quickly and has an excellent residual property of many weeks, making it a truly effective treatment.

The second day was largely spent vacuuming all of the dead flies, which we estimate were in their millions – we certainly disposed of more than 11KG in weight in numerous rubbish bags.

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An Effective Solution

Overall a job of astonishing proportions, but one that gave us huge satisfaction as these flies had made life extremely difficult for the resident and we were able to provide a highly effective fly control solution.

Who knows if next year will prove to be as challenging for cluster flies, but rest assured we have the experience to deal with any infestation, even ones as large as in this case study.

About Abate Pest Management

Abate Pest Management is a company that specialises in providing effective and sustainable pest control solutions. Our team of highly trained professionals is equipped with the latest technology and techniques to provide high-quality pest control services to their customers. If you are looking for a reliable and effective pest control service, contact our friendly team today on 0800 980 9767 or email us at