Nobody likes dealing with flies buzzing around their home, especially when they show up by the hundreds. If you’ve noticed large, slow-moving flies gathering near your windows during fall or winter, you’re probably dealing with cluster flies. These pesky insects are different from regular house flies and need special treatment to get rid of them for good.
Here are some effective methods to get rid of them and keep them from coming back.
1. Vacuum Them Up Right Away
The fastest way to deal with cluster flies you can see is to vacuum them up. When you’re learning how to get rid of cluster flies, this is often the first method people try because it gives immediate results. Since cluster flies are very slow moving, it’s easy to vacuum or even sweep them out of your home. They’re so sluggish that they won’t even try to escape when you come at them with the vacuum.
Use a vacuum cleaner with a hose attachment to suck up flies from windows, walls, and ceilings. Make sure your vacuum has a HEPA filter to prevent any potential allergens from being released back into your living space. This is super important because you don’t want to just move the problem around.
Here’s the key part: If you use a vacuum cleaner to clear up sluggish flies, remove the bag and place it outdoors, or the flies inside may crawl back out. Empty the vacuum bag right away into a sealed plastic bag and throw it in the outside trash. Otherwise, those flies might just crawl back out and you’ll be dealing with the same problem again.
This method works great when you’re dealing with flies that are already active in your living spaces. You might need to do this several times over a few days because more flies will keep coming out of their hiding spots when the weather warms up.
2. Set Up UV Light Traps for Ongoing Control
Light traps are one of the most effective long-term solutions for cluster flies. Light traps work well in large open areas like attics because these flies move through open spaces and are easily caught. The best part is that they work 24 hours a day without you having to do anything.
You can set up ultraviolet light traps in infested areas. They fly towards the light and get trapped. Modern UV traps use both blue and UV light to attract flies, then catch them on sticky surfaces. The most effective light traps operate at 10,000 cycles per second, making the light appear constant to flies rather than flickering.
For your home, you can get smaller plug-in units that cover around 600 square feet. These are perfect for rooms where you’ve seen cluster flies. For bigger spaces like attics or basements, you’ll want a larger unit that can handle 1,800 square feet or more.
Place the light traps in areas where you’ve seen the most fly activity, usually near windows or in attics. The flies will be naturally drawn to the light and get stuck on the glue boards. Just remember to replace the glue boards when they get full of bugs.
3. Use Sticky Traps and Flypaper
Sometimes the simple solutions work the best. Resin strips (flypaper) may be hung in infested areas if there is little or no air movement. Sticky traps and flypaper are cheap, easy to use, and completely chemical-free.
Hang sticky flypaper near windows or light sources to catch cluster flies. Since cluster flies are attracted to light and tend to gather near windows, this is where sticky traps work best. Just make sure to place them in areas where there isn’t much air movement, because breezes can make the traps less effective.
You can also make your own trap using household items. You can use a Mason jar with sweetened water and a perforated lid to lure and trap cluster flies. Just poke some holes in the lid that are big enough for flies to crawl through but small enough that they’ll have trouble getting back out.
Replace the sticky traps regularly, especially when they start getting full of flies. A trap covered in dead bugs won’t catch many more. This method works great alongside other treatments because it helps catch any flies that might escape your other control methods.
4. Apply Natural Essential Oil Repellents
If you prefer to avoid chemicals, essential oils can be a great way to keep cluster flies away. Getting rid of cluster flies naturally is possible with the right essential oil combinations. Peppermint, lemongrass, eucalyptus, lavender, citronella, and tea tree oil are some of the best essential oils for repelling flies. These oils contain natural compounds that flies hate but smell great to people.
A simple recipe for a fly repellent could be mixing ten drops of eucalyptus oil, ten drops of lavender oil, and a cup of water in a spray bottle. You can also try mixing 8 ounces of water with 10 drops each of peppermint, lavender, orange, and patchouli oils for a powerful repellent spray.
Certain scents, like lavender, eucalyptus, and peppermint, are known to repel flies. Consider putting these scents around your home through diffusers or organic room sprays. You can use an essential oil diffuser to spread the scent throughout a room, or you can make sachets with cotton balls soaked in essential oils.
Other natural options include fresh basil plants on windowsills, citrus peels near problem areas, or pine-scented cleaning products. The key is to use these scents regularly in areas where cluster flies like to gather.
5. Seal Entry Points and Cracks
This is probably the most important thing you can do to prevent cluster flies. Understanding how to get rid of cluster flies starts with blocking their entry points in the first place. Mechanical exclusion is the best method to keep cluster flies from entering homes and buildings. Cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath the fascia and other openings should be sealed with good quality silicone or silicone-latex caulk.
Buildings must be sealed before cluster flies move into wall voids and attic areas. Cluster flies begin moving into buildings for winter shelter in late August, and most move in during September. This means you need to do your sealing work by Labor Day at the latest.
Pay special attention to sealing sites on sun-exposed sides (south and west) and upper areas of the building where cluster flies are most likely to enter. These are the areas where flies like to gather before they find ways inside.
Check around windows, doors, where pipes enter your house, around electrical outlets, and anywhere else you can see daylight coming through. Use top quality silicone sealant because silicon-based caulking is elastic and flexible. This type of caulking lasts longer and moves with your house as it expands and contracts.
Don’t forget about screens either. Repair any holes or tears in window and door screens, and make sure they fit tightly. Even small gaps can let cluster flies squeeze through.
6. Consider Professional Fumigation for Severe Infestations
When you’re dealing with thousands of cluster flies in your attic or walls, fumigation might be your best option. Professional fumigation is often the most effective approach for how to get rid of cluster flies in large numbers. Smoke bombs can quickly and efficiently fill a space with insecticide smoke. This means that any infestation of cluster flies within loft spaces can be dealt with effectively.
There are two main types of fumigation products: smoke bombs and foggers. Smoke bombs release an insecticidal smoke that spreads throughout the room or loft space, getting into all corners, cracks and crevices. Foggers release an insecticidal gas under high pressure instead of requiring a flame.
Smoke bombs require a flame to start, so they create more of a health risk and fire hazard than foggers. You should consult a professional before doing this yourself. Foggers are generally safer because they don’t need an open flame and won’t set off smoke alarms.
One smoke bomb treats an area of about 120 cubic meters. Two smoke bombs will treat a standard roof space. For larger areas, you’ll need multiple units or professional-grade equipment.
This method gives you the fastest knockdown of a large infestation, but it only kills the flies that are present when you use it. You’ll still need to seal entry points and use other methods to prevent new flies from coming in.
7. Use Targeted Aerosol Sprays
For flies you can see flying around, aerosol sprays can give you quick results. An aerosol contact pyrethrin spray can be used as a space spray to get immediate relief. Consider pyrethrins, which are extracts from chrysanthemum flowers that kill cluster flies quickly. Use it lightly and aim it directly at the flies.
Recommended products include CB-80 or PT 565. These are pyrethrum contact aerosols that can be used as space sprays to kill on contact. Spray lightly and repeat as needed. The key is to target the flies directly rather than just spraying everywhere.
Pyrethrins are low in toxicity to humans and other mammals but toxic to fish, so keep them away from water supplies. Always read the label carefully and use these products exactly as directed.
This method works best for flies that are actively flying around your living spaces. It’s not going to help with flies hiding in your walls or attic, but it can give you quick relief from the ones that are bothering you right now.
Remember that aerosol sprays are just a temporary fix. You’ll still need to deal with the source of the problem by sealing entry points and removing flies from their hiding places.
8. Install Fine Mesh Screens
Good screens are your first line of defense against cluster flies. Install fine-mesh screens on windows, vents, and openings to prevent cluster flies from entering your home while still allowing ventilation. Regular window screens might not be enough because cluster flies can sometimes squeeze through larger mesh.
Repair gaps and tears in window and door screens. This will help reduce entry of flies, gnats, mosquitoes and midges during summer, and cluster flies and other overwintering pests in early fall. Even small holes can let flies through, so check all your screens carefully.
Install door sweeps or thresholds at the base of all exterior entry doors. Check for light coming under doors by lying on the floor and looking. If you can see light, flies can probably get through those gaps too.
Don’t forget about other openings like dryer vents, bathroom exhaust fans, and attic vents. These all need to have screens that are in good condition. Replace any screens that are damaged or have holes.
Good screens not only keep cluster flies out but also help with other flying insects throughout the year. It’s one of the best investments you can make in pest prevention.
9. Apply Perimeter Insecticide Treatment
Treating the outside of your house before cluster flies arrive can stop them from getting inside in the first place. To prevent cluster flies from entering your home in the fall, treat the outside perimeter with a good all-purpose concentrate. Pay particular attention to the south and west sides of the house.
Products like Cyzmic CS provide long-term protection and don’t break down easily on outside wall surfaces. It’s odorless and doesn’t leave stains or visible residue. These professional-grade products last much longer than regular bug sprays.
Apply residual insecticides as sprays targeted to cracks and crevices on the building exterior in late summer. This can kill some flies before they move behind walls or cause them to die shortly afterwards.
The timing is important for this method. You want to apply the treatment in late August before cluster flies start looking for winter hiding spots. Spray the building’s outside walls where cluster flies are likely to land and rest before entering the building.
This method works best when combined with sealing cracks and gaps. The insecticide treatment kills flies that land on treated surfaces, while the sealing prevents them from finding ways inside.
10. Maintain Cleanliness and Remove Attractants
Keeping your house clean and managing light sources can help reduce cluster fly problems. Routine cleaning, especially in corners and hidden areas, can reduce the number of places flies can hibernate. While cluster flies don’t eat garbage like house flies, they still benefit from a clean environment.
Turn off unnecessary lights at night, since cluster flies are drawn to light sources. Use yellow bug lights or keep blinds and curtains closed during the evening. You can also try a neat trick: turn off all lights in a room except one near an open window. The flies might follow that light right back outside.
Dead cluster flies on floors can lead to infestations of other insects, such as carpet beetles. Clean up dead flies where practical. Those dead flies can actually attract other pests that will eat them and then stick around to cause new problems.
Remove leaf piles, compost heaps, and other organic material near your home that may attract flies. While cluster flies don’t breed in these materials like other flies do, reducing attractants around your house is always a good idea.
Regular vacuuming, especially around windows and in corners where cluster flies like to hide, can help you catch problems early before they get out of hand.
11. Call Professional Pest Control Services
Sometimes the best solution is to call in the experts. Getting rid of cluster flies can be challenging when infestations are severe or keep coming back. Larger or recurring problems often require professional fly control because cluster flies are notorious for finding hidden spaces, such as wall voids and attics, which can make them difficult to eliminate without specialized tools and knowledge.
If cluster flies return year after year, it’s a sign that entry points haven’t been fully sealed, or that their hibernation spots remain undisturbed. Professional pest control technicians have the experience to find and treat all the places where cluster flies might be hiding.
Expert pest controllers have all the equipment to ensure safe and effective cluster fly treatment. They can use smoke bombs and foggers more safely than most homeowners can. They also have access to professional-grade products that aren’t available to regular consumers.
Professional treatments can include special dust that gets injected into voids behind walls and other areas where cluster flies gather. This type of treatment requires special equipment that most homeowners don’t have.
Consider calling professionals if you’ve tried several methods without success, if the infestation is very large, or if cluster flies keep coming back every year despite your best efforts. A good pest control company can create a comprehensive treatment plan that addresses both current flies and future prevention.
