February 5th, 2021 by Sarah Miles

Many household pests can be difficult to treat but there is one bug that depends not only on the right treatment but also on the right timing as well, in order to successfully eradicate it: the cluster fly. Although, as the name suggests, you’ll never be dealing with just one of these swarming pests.

What are cluster flies?

House flies are more common in warm weather, but have you ever noticed the odd fly that’s a bit smaller than a regular fly, in the winter? If you get close, they might more of a yellow or golden colour? Perhaps you've also noticed a strange, sweet smell coming from the loft? If the answer is yes, you may have an infestation of cluster flies.

As the name suggests, they gather in swarms of thousands, but don’t assume because you have only seen a few that they can’t be cluster flies as the majority will be hidden away somewhere dark, warm, and quiet; most commonly the loft. They occupy your home during the colder weather of autumn and winter and in spring they will leave to spend the warmer months outdoors, where they mate. You may now be thinking that if they will leave of their own accord, why bother trying to get rid of them? Unfortunately, this is not the end of the story.

The sickly, sweet smell that you can detect is pheromone, which is present in their saliva. They deposit this on the walls in the space they are occupying, often leaving unpleasant stains. However, these stains are the least of your worries. The pheromone acts as a marker and the flies will use this like GPS to find their way back into your home in the autumn, for another winter of your hospitality.

Time is of the essence

Timing matters because unless you deal with them before they leave in the spring, they will come back. The pheromone they deposit is specific to the flies that have been inhabiting your home so to break the cycle you need to eradicate the flies before they leave.

How to treat cluster flies

The biggest barrier to successful extermination is volume. Because there are literally thousands of cluster flies in one swarm, if you miss even 10%, they can return – having mated over the summer.

Having established that the first rule is to deal with them now, in the winter, let’s take a look at how you can get rid of them effectively.

Because of their number, you need to employ a holistic strategy that uses a variety of killing solutions. Use products that are specific to this particular pest for the best outcome. Using a combination of the 3 methods below will provide a solution that is greater than the sum of its parts and ensure a thorough job.

Automatic Pest Aerosol Dispenser

Clearly, a single blast of fly spray won’t touch the sides. This cluster fly dispenser from PreVent releases a fresh spray at fixed intervals to chip away at the swarm over a period of time. It also means you don’t have to spray them manually yourself, which would not be a pleasant job.

Cluster Fly Automatic Dispenser and Triple Prevent Auto Package

Price: £50.95

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Smoke Bomb

A smoke bomb, also known as a fumer or fogger, will fill the whole space with insecticide and even penetrate into small gaps and cracks, where you would struggle to get into with a spray.

Electric Cluster Fly Killer

Standard electric fly killers will kill cluster flies, but their trays will quickly fill up, due to the numbers involved. Not only will this compromise performance; it can even potentially become a fire hazard. One with a deep tray that is designed to be able to keep up with cluster fly extermination, such as this one from Insect-o-Cutor, is an excellent option for dealing with them.

Insect-O-Cutor Select SE22 White Metal Electric Fly Killer 22 Watts

Price: £245.99

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Just as you need several treatment types, it pays to repeat treatments multiple times to ensure that you have eradicated the whole infestation. A zero-tolerance policy at this stage is definitely preferable to being put back to square one in the autumn because they’ve been allowed to return.