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How to get rid of Cluster Flies

Cluster flies often confused with house flies belong to a family of flies called Pollenia and are medium sized, about 10mm in length. They are greyish olive in colour and adorned with golden hairs which makes them quite distinctive to the trained eye.

Closeup of a cluster fly

They get their name from their characteristic behaviour of congregating in groups of hundreds and even thousands in lofts, small spaces and around windows.  

Continue reading to get expert tips on how you can get rid of cluster flies with ease.

How do cluster flies enter my home?

Cluster flies like to enter around window frames, especially casement and sash windows, where they leave significant deposits of fluid and faecal residues with an offensive sickly smell.

They also have a tendency to make their way into homes through any cracks and crevices they can. Blocking some of these entry points can be a good way to prevent them entering.

Cluster flies may hibernate in the warmth and shelter of our lofts and the growing popularity of ceiling halogen lights means that large numbers of flies can collect around the light fittings and potentially create a fire risk.

Cluster flies entering through window frames

Signs of a cluster fly infestation

If you believe you may have a cluster fly infestation use these common signs to know for sure.

  • A sickly rich smell
  • Swarming flies if disturbed.
  • Large number of flies in windows.
  • Fly faeces around windows.

Where are cluster flies usually found?

Cluster flies in windows are very, very common along with infestations in lofts.

Other common places you are likely to find the flies are the internal weight cavities or shafts of sash windows, internal frame cavities of double glazed units, wall voids and any other cracks and crevices.

How to get rid of cluster flies

If you discover a loft full of flies, the most effective weapon is a cluster fly smoke bomb. This will stop any active flies in their tracks and allow you to deal with the hidden ones.

Use the mentioned sprays below on all surfaces to neutralise the pheromones and set up a timed insecticidal spray such as the Prevent Auto Dispenser. This can be set to spray insecticide at intervals, thereby targeting any flies that emerge from harbourages and perpetually addressing the pheromone problem.

For unsightly clusters of flies on sunny windows, the Cluster Buster is the perfect weapon. Consisting of a unit filled with a ‘quicksand’ of crushed shells which traps the flies and uses the pheromone release to attract more flies it is toxic free and an all round winner.

We sell a range of cluster fly killer products including cluster fly killer sprayscluster fly traps and cluster fly smoke bombs. Below are some of our handpicked recommendations.

Cluster Fly Fumers

The key challenge when fumigating is timing. You need to ensure that any fumigation product is used when it will be most effective.

Cluster fly smoke bombs, available in 3 sizes are a good way to treat problem areas and are very effective at reaching inaccessible as the fumes will penetrate all cracks and crevices where they may be hiding. Simply, place the fumer on a slate or tray and light the touch paper.

Cluster Fly Sprays

An alternative way to kill cluster flies is by using the Prevent Auto Dispenser. This dispenser contains a pyrethrum based insecticidal spray which will activate at several intervals over a 24 hour period. This is effective at killing cluster flies as they enter to hibernate.

If you have a problem with cluster flies in your windows, Dethlac is the best spray to use. It is a lacquer based insecticide that dries into a hard layer and it remains active for a number of weeks.  Just spray into the window cavities and it will kill any flies that come into contact with it.

Cluster Fly Traps

If you are looking to trap cluster flies we highly recommend using the Cluster Buster Trap. This trap contains a quicksand made of exploded eggshells.

The natural behaviour of the cluster fly leads it to fall into the trap where it becomes stuck in the quicksand. The more flies that get trapped, the more pheromone the insects emit, so attracting yet more flies

Each trap will hold about 1000 flies and normally lasts about 2 years. For maximum effectiveness, place a unit on each window.

Cluster Fly Control Kit

The Cluster Fly Control Kit is a handy kit containing products that will help you control and treat Cluster Flies in your home.

Each kit contains:
1 x Prevent Auto Cluster Fly Killer Spray Dispenser
1 x Prevent Auto Cluster Fly Killer Spray Aerosol
1 x 400g Residex P
2 x 15g Insecto Midi Cluster Fly Smoke Bomb

What causes cluster flies in the house?

Cluster flies are common in the loft and attic spaces of homes and business premises. The warmth generated here means that flies are naturally drawn into these cavities and voids, particularly during the months of October and November, where they congregate in groups or clusters.

Cluster fly infestation in the home

Can you prevent cluster flies?

It is generally said that prevention is better than cure, but in the case of the cluster fly, this adage is of little use.

Proofing contaminated areas is largely pointless. Your property requires ventilation to breath and without sufficient air flow, mould and rot would set in. 

What damage do cluster flies cause ?

None – unless they are present in significant numbers. Even though they don’t cause damage they can be of high annoyance due to the large numbers they travel in.

Do cluster flies pose any health risks?

Cluster flies have no recognized importance as carriers of disease, so are not a significant pathogenic risk. They should only be viewed as an unsightly nuisance and not as a sign of poor hygiene.  

What is important to think about  is that cluster flies will hibernate with other flies that ARE carriers of disease, such as blow flies found on faeces and rotting meat, the latter possibly attracted by the smell created by large cluster fly populations.

Make sure to dispose of any dead cluster flies that may be present after treatment.

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