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What you can do to reduce/eliminate cluster flies

How to reduce cluster fliesWhen autumn arrives, and with winter just around the corner, you may find cluster flies are beginning to bug you in your shed (and even in your house). While this time of year tends to make some insects and pests less active, the colder temperatures make cluster flies come out in full force.

While cluster flies can be notoriously difficult to get rid of, there are some actions you can take to reduce the problem and potentially eliminate them altogether. We’re going to give you an explanation of what cluster flies are and why they love spots like your shed to reside in over winter, as well as share some tips for eliminating them so you can claim back your shed.

What are cluster flies?

Cluster flies are medium to large-sized flies (approximately 8-15mm in length). They have a dark grey abdomen and commonly have deep red eyes. Their most distinguishing feature is the lines on their head and gold hairs on their thorax. Their larvae feed on earthworms in grass pasture or lawn grounds, and the adult flies hibernate for the winter in sheds and other buildings.

They truly live up to the name ‘cluster flies’ through their tendency to congregate in large groups or swarms in dark places including the likes of sheds, attics, dark corners, crevices, and more. They have a unique ability to release a pheromone that attracts other cluster flies. Not only do they attract one another to the spot they’re residing, but this pheromone also lingers long after the flies have been removed - it can stick around for years! That’s why it’s crucial any treatment is continued, even when there are no longer flies there.

The reason these flies congregate together is simply to survive the winter as once it begins warming up they come out of hibernation to lay eggs on any surrounding grassland. Their lifecycle from earthworm-eating larvae through to adult flies then perpetuates until they must head inside again for winter hibernation. Cluster flies are certainly a nuisance, but they won’t reproduce within your shed and don’t carry disease. The only damage they really cause is an annoyance and tiny dark spots of excrement which is unsanitary. So, how do you get rid of them?

top tips to reduce or eliminate cluster flies in your shed


Prevention is key

Cluster flies can be difficult to get rid of once they’re there. This is a direct result of the pheromones they excrete as they can linger around for years after the initial infestation has been removed, attracting more and more flies. So, before any cluster flies select your shed for their winter hibernation home, you’ll want to pest-proof your shed. We recommend using the following preventative measures to keep cluster flies away:

  • Ensure your door(s) and window screens are in good shape with no holes or cracks.
  • Be sure to seal any cracks, crevices, and holes you can find on the outside of your shed, including checking any cable penetration points.
  • Using a spot treatment for cluster flies outside during the summer will help to reduce their populations and prevent them from coming inside over the colder seasons.

Use pesticides and maintain a clean shed

If you’ve found a cluster in your shed, you’ll first need to spray it down with pesticides to ensure any existing flies are exterminated. To remove them, simply use a vacuum. Following the removal, the area will need to be thoroughly cleaned and disinfected. Also, any spot where there could potentially be pheromones will need to be treated. Once this is done, it’s wise to investigate the outside of your shed to ascertain where their entry point(s) could have been and to disinfect these areas. This will reduce the likelihood of them coming in through those same entrances. It’s always helpful to enlist the help of a professional in this instance as the chemicals required to exterminate cluster flies can be harmful to humans if ingested.

Fill in any broken seals or cracks/potential entry points throughout your shed

Shed repairsGo hunting for any potential openings on your shed and make sure you seal those cracks! Common places where this can occur include around windows and doors. If there are no places for cluster flies to get into your shed, you’re setting yourself up for success.

Additional methods of getting rid of cluster flies

There’s an array of different methods you can employ to remove cluster flies from your shed. While some can be more effective than others, so long as you’re putting something in place to get rid of them, you’ll be in a better position than you were yesterday! Below is a list of different things you can try to eliminate cluster flies from your shed:

  • Foggers (performed by a trained professional).
  • Smoke bombs (performed by a trained professional).
  • Install fly screens over your windows.
  • Insect spray.
  • Citronella fragrance wick.
  • Electric fly killers.
  • Fly boxes.
  • Vacuum cleaner.
  • Sugar water jars.
  • Maintain a clean shed (clean up food and drink spills or open rubbish quickly).

Ultimately, cluster flies are unhygienic and are an annoyance that nobody wants to deal with. However, if they do so happen to find a hibernation spot within your shed, there are a few tactics you can use to reduce or even eliminate the problem entirely.

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