February 17th, 2021 by Sarah Miles

Pests often have a specific life cycle that means there are optimum times for dealing with them. If you have cluster flies; that time is now. If you leave it too long, you will find that they will eventually leave of their own accord but only temporarily and you’ll be back to square one come the autumn.

What are cluster flies and how do you know if you have them?

Cluster flies are slightly bigger than regular house flies and slightly golden in colour. They gather en-masse (hence the name) but you may only spot the odd one as they tend to stay hidden away. The most significant sign that you have them is a strange smell, most likely coming from the loft.

Why is it so important to deal with cluster flies before the spring?

Cluster flies like warm weather so they spend the spring and summer outdoors, where they mate, but seek refuge indoors in dark, quiet spaces – hence lofts. While there, they rub their saliva into your walls which leaves a stain and the sickly, sweet smell you may have detected. This is pretty unpleasant for you, but more importantly, it’s also a strategy for finding their way back into your home once the weather starts to turn cooler again. That’s because their saliva contains a pheromone which acts as a marker and guides them back.

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It's pretty much impossible to remove all of the pheromones once the swarm has left as tiny traces can be impossible for humans to detect, so you have to deal with them before they leave in the spring. The pheromone is specific to those particular flies so exterminate the flies and you break the cycle.

How to eliminate cluster flies

There are two main elements of getting rid of cluster flies: the first is timing, as detailed above. It’s imperative to deal with them before they leave in the spring. That means tackling them now. The second is to attack on several fronts; as with any pest, relying on a single type of treatment can allow some insects to adapt, resist, and survive.

Their main defence is in numbers. There are so many of them that they are likely to overwhelm standard fly treatments and if you miss any, they can come back.

By using a variety of killing solutions you can cover all bases and deal with them thoroughly and completely. Products that are specifically designed for these insects are going to give you the best results. Try a combination of the following:

Smoke bombs – smoke bombs are very effective because they can penetrate the smallest of gaps and cover large areas. As well as killing the flies, they will flush any that are hiding, in tiny cracks and holes, out into the open.

Electric cluster fly killers – these work in the same way that regular electric fly killers work but are equipped with deeper trays and a high-capacity zapping grid to be able to work effectively with the greater volume.

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Automatic aerosol dispensers – just like automatic air fresheners release a fresh spritz at regular intervals, so these dispensers release a dose of pesticide periodically. It means that you don’t have to be up there, spraying them manually.

Repeat the treatments

Because there may be thousands of flies in the swarm, to really do the job belt and braces you need to repeat these treatments several times to ensure that you have got them all. Flies can squeeze into the tiniest of cracks to escape danger, so you may need to employ a bit of perseverance to keep coming back to the loft and thinning the swarm. However much of an inconvenience this may seem at the time, it is so much better than seeing all your efforts wasted because they’ve returned the following autumn.