The house fly
Have flies invaded your home and you don't know where to start to get rid of them? Because of the speed with which they reproduce, a fly invasion means you have to fight them every day. In this dossier, you'll find a range of answers and natural products to help you combat this invasive insect.
I would like to
Order : Diptera
Family : Muscidae, Fanniidae, Calliphoridae
Size : 4 to 10 mm
Location : any habitat
Period : all year round
Of all the flies that can enter homes, there are 4 main species :
- the housefly (Musca domestica),
- the stable fly (Stomoxys calcitrans),
- the small housefly (Fannia canicularis),
- Attic fly (Pollenia rudis).
The adult fly feeds on plant and animal debris, sweat, excrement and blood (stable fly). The larva feeds on manure, detritus and rubbish.
The fly is highly invasive
Flies have colonised every part of the world where humans live.
Present from March to mid-November in our homes in various forms (larvae, nymphs), it doesn't stay indoors all day : in the evening, it takes a trip to the garden, the compost, the manure or the duck pond.
In the summer, they take up residence in the cool, dark living rooms, and in the attic during the winter.
Although not very pleasant, most species of fly are useful in our ecosystem (food for birds and fish, transforming compost into humus, etc.).
How does a fly walk on the ceiling without falling ?
Microscopic view of the tip of a fly's legAs you will have noticed, the fly is an exceptional acrobat ! It's the most gifted of all insects when it comes to moving around upside down. But... it's not magic ! Sorry to disappoint you ! It actually has what look like suction cups on its legs.
In fact, at the end of each leg it has 2 curved claws, 2 adhesive side pads and a 3rd pad called the empodium. It is this whole system that enables flies to literally stick to ceilings or smooth vertical surfaces. Of course, other insects other insects can do it (bugs, beetles, wasps, bees, ants, etc.), but flies are still the best equipped to perform this kind of feat !
Flies also have a high surface-to-volume ratio. In other words, they occupy a small volume for a large body surface area. Because of their low mass, they are more subject to surface forces - such as adhesion to the surface they are on - than to the force of gravity.
What attracts flies ?
1 - Smells : In the house or flat, flies are attracted by smells. Whether it smells "good": perfume, fresh food (raw or cooked), sugar, fruit, vegetables, vinegar, etc. Or "bad": decomposing organic matter, excrement, sewage odours, rubbish, etc.
And the hotter it gets... the more the odours are amplified. It's easy to see why there's an abundance of flies in homes and other places in summer. Some flies are baited by us humans, because we are made up of sodium and other minerals (tears, perspiration) that are salty.
2 - Decomposition foods : vinegar flies are most attracted to fruit and vegetables that are too ripe or rotten. But that's not all (unfortunately), especially on hot days. They are particularly fond of used tea or coffee capsules, wilted or decomposing bunches of flowers, organic matter in rubbish bins and the bottoms of drinks (bottles or glasses of beer, wine, vinegar or cider). They are totally seduced by all these acidic and/or sweet foods.
3 - the farm and stables : These areas are full of odours that flies are particularly fond of (especially autumn flies). Cattle, horses, ponies, donkeys, etc. are very popular with these little creatures. They feed on the fluids they secrete around their eyes, mouths and snouts. What's more, manure, fertiliser, fresh excrement and organic or vegetable matter attract flies, which sense the potential for reproduction in these places, especially if it's hot.
Flies carry germs
This insect is one of the main carriers of germs. Its body is teeming with millions of bacteria and it often deposits them on food.
The reserves accumulated during the larval stage are enough to keep the adult alive. It does, however, need a supply of sugar, which comes in a variety of forms: nectar, pollen, honeydew, milk, sweet liquids, meat, fruit, etc. Although they are not great travellers, flies can cover several kilometres in order to feed.
The partially digested liquid substances are then sucked up. While it feeds, it regurgitates part of its previous meal (the famous fly droppings!) and it is mainly in this way that it transmits pathogenic microbes to our food.
So be careful not to use ultraviolet traps or electric grids. As soon as the fly comes into contact with these devices, it explodes and the debris full of pathogenic micro-organisms spreads over a radius of 3 metres, contaminating everything.
The fly reproduces very quickly !
Reproduction takes place in summer, when conditions are most favourable. A fine summer suits it, but too much heat is fatal: above 30°C, it becomes sterile.
Its preferred breeding areas are warm, damp places such as rubbish dumps, uncovered human excrement, droppings, rubbish, carrion, manure, dung, meat, cheese and rubbish bins.
Depending on the heat and humidity, the eggs hatch after 8 to 24 hours and become larvae (also known as maggots), then nymphs for a short period, before transforming into flies proper.
The adult lives for 10 to 12 days. There are 10 to 30 generations per year.
A single female can lay up to 1,000 eggs, in several clutches of 150 eggs each. Under the best conditions, she can mate 2 weeks after hatching and lay eggs 4 days after mating.
Special fly sprays containing pyrethroids fortified with DDVP should be avoided, as flies can easily develop resistance to sprays due to their rapid reproductive cycle.
Also beware of insecticides beginning with "BIO" that contain permethrin (an organochlorine pesticide in the pyrethroid family). Although this product is biodegradable, there is nothing natural about it (synthetic) and even less organic about it. The toxicity of permethrin to humans has not yet been classified, but it is highly toxic to all cold-blooded animals and is not tolerated by cats (it can cause convulsion-type symptoms).
Also look out for insecticides that say "naturally active" in bold type. Manufacturers know how to attract your attention and sell you products that are not as natural as they claim. Most contain other ingredients such as PBO (pyperonyl butoxide) or permethrin !
At Penn'Ty Bio, we offer natural insecticides with no additives or petrochemicals.
Our tips for reducing the number of flies
1 - Keep rubbish away and maintain an impeccable level of cleanliness
Before any curative action is taken, a number of preventive measures can be applied to limit the presence of flies. In your home :
- Deep clean behind your furniture and appliances.
- Clean the bottom of your bottles of soft drinks, vinegar, spirits, etc. before storing them.
- Keep doors and windows closed at night, otherwise install a mosquito net.
- Protect your fruit and vegetables with bulk bags or protective covers.
- Have a dustbin with a tight-fitting lid and wash it twice a month with vinegar and water.
- Clean up after your animals (clean bird feeders, you can even remove the food for the night).
And in farm, stable or henhouse buildings, if you haven't already done so, you need to apply a minimum of basic rules to limit their reproduction and feeding :
- Keep all piles of manure, rubbish, sewage, rubbish bags, etc. away from the building. all decomposing organic matter.
- Clean out the ventilation systems to dry out the buildings.
- Always keep drinking troughs and feeding troughs clean.
- Do not leave milk deposits near the milking parlour or feeding area.
- Bedding should be as dry as possible (water troughs at the right height, renewal, ventilation).
- Slurry pits: stir regularly to destroy developing larvae.
2 - Touching breeding areas
You should try to stop their development by treating all the areas where they can reproduce with our 4J insecticide diluted to 5% (allow 500ml / 5m2 of surface treated).
3 - Mass elimination
You should try to destroy as many flies as possible. The more flies there are, the more they will lay eggs and the more you will have. There are many ways of doing this, but they're not always effective ! Flies are still 100% difficult to kill.
3a. Mechanical methods
These are still the easiest to use and are in no way harmful to us or our environment: the timeless fly swatter. Its long handle and flexibility make it a formidable weapon ! Then there's fly tape, of course, as well as fly strips for windowsills and hoovers.
As far as the hoover is concerned, avoid leaving flies in the bag, otherwise you risk ending up with a colony of larvae! You can spray an insecticide through the suction tube, but be careful never to use a flammable insecticide, otherwise you risk your hoover catching fire.
3b. Chemical products
Most shop-bought products are not always effective and, above all, not always healthy. Read your product label carefully, especially the precautions for use. Don't forget to look out for the mandatory pictograms !
To treat the air in your home, use Ecodoo aerosol or Aries flying insect repellent, 2 products composed of plant alcohol, essential oils and plant pyrethrum, specifically developed to combat flying insects. This type of product is highly effective, but only occasionally, as the flies will return as soon as you open a window or door! Plant pyrethrum without additives does have its advantages, but its shelf life is limited (it doesn't last very long), so you'll need to use it regularly. All Insectes Pistal insecticide can also be used as a direct spray. Immediate effect !
Finally, still on the subject of fumigation, Habitat Biovétol fogger will give excellent results on this type of insect. An insecticide based on active ingredients of plant origin (pyrethrum + geraniol), designed for basic treatment of the home. Highly volatile, the solution settles in the smallest nooks and crannies where parasites and insects live. Immediate action. 3 different formats are available: 75ml for treatment of less than 15m², 150ml for treatment of less than 30m². Finally, 250ml, for a treatment of more than 30m².
4 - To keep them at bay
Once the number of flies in the room has been reduced sufficiently, you can protect your space against the intrusion of new flies. You'll need to treat all the places they can enter (curtains, net curtains, door frames, etc.) as well as all the surfaces you want to protect. The aim is to create a repellent volume.
But, I'm sorry to say, there's no such thing as a miracle repellent! At best, a repellent will protect a few dozen centimetres around the treated surface. The more surfaces you treat, the better protected you'll be, but you won't get rid of all the flies.
4a. Our Pyrethrum/Geraniol insect repellent has been shown to have a highly significant intrinsic repellent effect (94%) on flies (and 98% on mosquitoes) when applied directly to the inert surface, as well as a residual repellent effect lasting two weeks. Use 500 ml to treat 5m².
4b. Our second Habitat Insect Repellent containing Eucalyptus citriodora will also give very good results and provide an ideal barrier against flies.
4c. Aries fly repellent offers another solution for protecting surfaces over a short period. It is available either as a spray or a concentrated solution (it can be used pure or diluted to protect the floor or garden furniture, for example).
4d. In terms of repellency, our mosquito and flying insect repellent spirals will keep flies at bay. The smoke from these spirals is made from pyrethrum. Flies will be immediately disturbed and will move on, or even die if they insist. Up to 5h30 of combustion per spiral.
And if you have a horse, pony, donkey or even a cow, our ALT'O ZINSECT insect repellent (spray or gel) will be perfectly suited to protecting them from the flies that swarm around them during the summer months. A 100% plant-based formulation combining 3 recognised, highly effective active ingredients to keep those nasty flies that spoil their daily lives at bay.
5 - 100% natural methods
- Known since the Middle Ages : In the event of a massive infestation in a room, close the shutters in the middle of the day to create half-light, leaving only one shutter ajar and the corresponding window open. Attracted to the light as if by a magnet, the flies will all be out within an hour or two.
- The traditional homemade trap : glass trap or plastic bottle to hang or place on the floor, add water and honey or a little sweet syrup, the flies will be attracted by the sugar and will drown in it. If you're using a plastic bottle, don't forget to collect the top of the bottle and turn it upside down to create a funnel on the bottom.
- Cloves and lemon : Stick cloves into lemons or other citrus fruit and place them in windows and doors. Replace them every week, as this will repel flies.
- Vinegar : Dilute white vinegar in a little water and place the mixture on your windowsill. Flies will no longer dare to set foot there. Washing your home with white vinegar is doubly effective, as it disinfects your home and repels flies.
- Essential oils : Geranium, peppermint, citronella, basil and eucalyptus essential oils are hated by flies. Put a few drops on your clothes or in a dish. There's no need to mix oils - just one is enough to get rid of them.
- Herbs : Place a few stalks of basil, mint or lavender around your home to repel flies. Alternatively, slice up some garlic or onions and place them in bowls on the windowsill, and that's all there is to it.
- Milk and sugar : Trap flies that are already in your home by creating a trap using milk, sugar and pepper, which they will then drown in.
Showing questions about fly
Q: I'm interested in your products, particularly the Insect Repellent, but to help me make my choice, could you answer the following questions ? - I live in the countryside, surrounded by fields, livestock and next to a pond: so flies + mosquitoes + spiders + cousins.... Is it better to use the "ready-to-use" repellent or to use a more concentrated dilution ? - My house has 10 windows + 1 bay + 3 external doors + 1 terrace: how much do I need to spray them ?
A: Don't expect to get rid of all the insects in the house, especially spiders, with a repellent product. The more concentrated a product, the greater its range of action. It depends on what you want to treat to limit the penetration of flying insects. Shelf life depends mainly on exposure to sunlight (degradation) and heat (evaporation). Let's say every week to start with, increasing or decreasing the frequency depending on the result. A 0.5l spray bottle will treat 5 m2 of surface area, but only treat non-absorbent surfaces, otherwise the product will penetrate the surface and lose its effectiveness. Preferably treat curtains rather than uprights, especially for 80 cm openings.
Q: We are invaded by flies. We have cows not far from our house (see the black ceiling of flies mainly in September) but there are flies all year round. Do you think that with these 3 products, insect spray + repellent spray + fly repellent, we could get rid of them ?
A: It's very difficult to get rid of flies completely unless you eliminate the source of the proliferation. However, when used correctly, repellents can help you to have far fewer flies. Insecticide is only useful for killing them by spraying on them. There are also fly repellent granules and tapes.
Q : Isn't there a risk of my dog being poisoned if he swallows insects (mainly flies) that have died with your product?
A: There is no danger, the product itself is not dangerous in normal use, and even less so eating treated insects.
Q: We have a septic tank and as soon as the weather's fine we get flies coming out of it and we've actually got some in the house; do you have a solution ?
A: I also have a septic tank but I don't have any flies. The tank is perfectly watertight, so I think that's the solution, but if that's not possible, you can always use fly repellent, granules or ribbons to combat them.
Q : Hello, can you tell me if I should use the anti-fly concentrate plus insect repellent for more effective action against stable flies. We're in the countryside next to a farm with cows and sheep. Thank you
A: ARIES fly repellent (concentrate or spray) is a good repellent. I also know that our Penntybio repellents are effective on flies (the pyrethrum-based one and the eucalyptus citriodora-based one). It's up to you to use them according to the surfaces to be treated. There are also fly repellent granules and tapes.
Q : I own a flag in the campaign. My attic is finished, my problem is that for several years in the unfinished part, I find hundreds of flies on the ground. My roof is in flat tiles and I have no roof, flies can pass. I don't have a dead bird either. Can you tell me why I have so many flies there and tell me what solution could I adopt to remove them. Would a treatment be worth trying despite the fact that my attic is of course ventilated ?
A: Finding dead flies in an attic is normal. Often they manage to get in but not get out. On the other hand, that there are a lot of them, that is not normal. I have no explanation, this happens frequently in sparsely occupied vacation homes. Our insect repellents are effective on flies. They allow a protection of 2 to 3 weeks. Apart from treating your tiles on the inside, I don't see too many other solutions. We have never tried this technique !
Q: My attic is invaded by flies and it even makes noise at night, there are so many of them. Can you tell me which is the right product? Thank you in advance and congratulations for your site and your products.
A: It is not easy to treat in an attic, considering that the space is often very ventilated. We can try to treat the interior roof with our insect repellent, this should limit the entry of new flies. At the same time, you can destroy the flies already present with our 4J insecticide.
Q : For 3 years my dog has been attacked by flies since April and this for 7 months. They suck his ears in particular so much that he bleeds and that every day. I have already tried various products, in particular grindstone for horses, I would like to find a product that is much more effective and that I don't have to apply every day.
A: We only have one product that might be suitable: ALT'O ZINSECT spray or gel insect repellent. which you will find on our website.
Q : In summer I have a lot of flying flies and mosquitoes in my apartment, could you advise me on essential oils or repellent. On the other hand I have a cat and I have heard that essential oils are toxic for them. What is it really ? THANKS
A: You have a ready-made blend on our site in Essential Oil Synergies: Peaceful Nights. For the cat, essential oils can be dangerous but only when applied to the skin (see our thematic file on this subject).
Q: We live in a house with a large bay window (2.40) and many openings (windows) and since the beginning of summer we have been invaded by flies. What should we do to try to reduce this nuisance, knowing that we have 3 children aged 8, 6 and 2 years old. So we don't want to use toxic and dangerous products. Give us the procedure to follow and the products to buy. PLEASE THANK YOU
A: You don't have a lot of solution, either natural or chemical. The only solution I see would be to put curtains in front of the bay window. You can possibly treat with repellent; for small openings, treat only the frame. To kill them, you also have the pellets and the tapes against the flies.
Q: We get swarmed with flies on the patio when we have lunch or dinner. Do you have a repellent to diffuse in order to keep them away effectively ?
A: Unfortunately, there are not many fly solutions. Personally, I kill them by spraying them with 4J insecticide diluted to 5%. If you have a lot of them, I recommend a garden type sprayer and you water them all. After a few days they should go away. You can also place our fly pellets in a corner.
Q: 10 days ago, the smell of rotting flesh was detected in my cellar. Of course I immediately tried to find the decomposing animal in my garden. Unfortunately it seems to me that this one went to die under my stone staircase, an inaccessible place... Currently, maggots (fly larvae) have invaded the ground bordering this staircase. What can I do to eliminate them ? I know the best way to do that is to find the body; but in my case it is almost impossible !
A: In this case, it's actually quite complicated. There remains the solution of treatment by fumigation using our Habitat Biovétol fogger. By trying to place it as close as possible so that the fumes enter under your staircase. As for the corpse, if you don't have access to it, you'll have to wait for it to decompose on its own.
Q : My mother lives in an old house and the toilets are original, septic tank. It is invaded by flies and we cannot destroy them. Can your product be put in the pit, safe for my mother and will she be quiet afterwards, no more invasion. Please let me know your answer because I don't know what else to do.
A: I don't really see how to use our products which are biodegradable in a pit full of bacteria! You can treat the flies present but you cannot prevent them from returning. I also have a septic tank but I don't have any flies. My pit is perfectly sealed and no fly can enter or leave. See rather on the side of your pit what can be done.
Q : I am looking for a fly repellent which we are regularly infested with in the summer when leaving windows and doors open, something non-toxic for humans, we have young children.
A: We have various repellents on our site, exclusively based on natural products which give good results in repellent. Another solution, to kill them, you have our 4J insecticide or granules and tapes against flies.
Q: I am a farmer and I have lodgings on the farm and I am invaded by flies in my buildings. I would like documentation on this subject. Also if you have a stand at the agricultural fair in libramont (Belgium) let me know thank you for your response.
A: We have various repellents on our site based exclusively on natural products which give good results as a repellent. Another solution, to kill them, you have our 4J insecticide or granules and tapes against flies. Due to lack of time, we are not taking part in any demonstrations.
Q : We have a small rabbit farm and are being invaded by flies this year. can we use your insecticide in the building where the hutches are located: is it safe for rabbits ? what concentration to choose knowing that the building has openings (which do not close and on which we have placed mosquito nets) ?
A: You can safely use our insecticide on your farm. It is authorized in organic farming. For flies, they should not go below 5% (standard concentration for all insects). You can treat with insecticide all the surfaces where the flies are in order to eliminate a maximum of them.
Q: I am a poultry farmer. I have problems with speckles breeding in droppings. How do I get rid of it? The surface to be treated is 2000 m/2 and this twice a year. Which product? What success ? How much per treatment ? What price ? Delivery in Belgium possible ? Thank you
A: The three strengths of our insecticide are: non-toxic, insect killing and egg killing. As speckles are small insects, I think a 2% concentration should be enough to try. To be effective, we recommend 1l of insecticide / 10m2. You can first take a small bottle of insecticide to do some tests and if the result suits you. Thereafter, you can consider treating all of your surfaces. We deliver in Belgium without worry (see shipping costs table).
Q: I don't know which product to choose. We are going to live in the countryside near the stables and we have flies galore, plus tiny "wasps" that sting. The main room is 70m2, and is duplex. We have a parrot, 2 cats and dog. What can you advise us in this context, which is more than effective and above all non-toxic for us and our animals ? There are too many choices, and I'm a little lost. Do you have anything else as effective that isn't in sprays ?
A: To protect against flies and safe to use and not spray you have: sticky tape and fly pellets.
Q: I have a chalet in the mountains (1600 m), and I am invaded by flies and horseflies, especially on the larch facades and then inside. What effective and lasting treatment do you have to offer me ?
A: For exterior treatment, we can offer you our repellent to spray on facades, but you should know that no natural (or unnatural) product resists the sun for very long. It can be used indoors. Otherwise, it is possible to use the traditional fly catcher tape, not very aesthetic but effective, and the granules, well placed, are effective.
Q: We have thousands of flies on our front walls (we are near a cow field) What do you recommend ? Do you have points of sale in department 69 ?
A: You have the solution to kill them, at least those on the facade, with our 4J insecticide diluted to 5%. Equip yourself with a garden-type sprayer and water the flies. Those touched by the product will die. It won't stop other flies from coming. You can start again until you run out of flies or product! we can also treat the wall with our insect repellent but if it lasts 3 weeks, in direct sunlight, it will last much less.
Q: I want to diffuse essential oils in my house, in addition to the insecticide and repellent you offer, to drive away many flies. Indeed I have a large bay window and I think that the repellent will not be enough, and moreover I am a little afraid of staining my fabrics so I will complete by diffusing. What mix do you recommend ? I was thinking of taking geranium, lemongrass, thyme, lavandin, cloves. Knowing that I have a 1 year old little girl, can it be dangerous, what essential oils should I avoid ? I think I'll also take your "child's night" mix for her since it's made on purpose; on the other hand, you specify on your page not to use essential oils before the age of 3, which is why I am wondering about my "anti-fly" broadcast !
A: If for mosquitoes we know the effective essential oils to keep them away (since the goal is to mask human body odor), for flies, it's a little more complicated. I have no idea of the essential oils to use, however I do not recommend diffusing thymol or even cloves in the presence of young children. You will find information on the diffusion of essential oils on our site.
Q: I have received your email, concerning insecticides, but I would like you to tell me which product is effective against flies, which have been inhabiting my attic for at least 4 or 5 years, despite a roof remodeling where they have not found nothing, as well as having used the "KAPO SHOCK CRAWLING FLYING" smoke product several years in a row, we are unable to stop this invasion. thank you for giving us the miracle solution.
A: We regularly have requests like yours: a fly-infested attic. If there are flies present, it is because they are finding something to reproduce (animal excrement, corpses, manure, etc.). The question is, do they breed outdoors or indoors ? Is your attic closed and insulated, do you have Velux windows ?
Q: We have a closed, insulated attic that is all black. When we look with a lamp, we do not see flies flying, nor dead. On the other hand they manage to go down in the rooms below, certainly attracted by the light, but impossible to see them leaving a precise place, except to see them dead in front of the windows, that is to say the light. Is KAPO CHOC CRAWLING FLYING SMOKE powerful enough, because we have been using it twice a year for at least 3 years. Do you have another product to offer us or to experiment with ? the rooms are not occupied.
A: In general, flies are attracted to warm, bright places. Flies are rarely found in a dark place. Why do you think the flies go through the attic since you can't find any (neither alive nor dead) and this place is dark ? It is possible that they arrive directly in the rooms without going through the attic. The Kapo is effective, it will kill the insects present in the room but that's all; it will not kill the insects that are behind a partition or those that will come after. Unfortunately, there is no miracle product to fight the fly apart from attacking the source of the proliferation, but when it is behind a partition, it is impossible or block all access with silicone. We brought in some very effective special fly pellets from Kapo.
Q: My attic is overrun with cluster flies (Pollenia rudis). What product from your range would you recommend to scare them away? I do not necessarily seek to kill them, but to dislodge them because they come out at the first ray of sunshine and "decorate" by the thousands the white facades of our house. Is the smoke pyramid effective for these flies ? What is its duration of action in repellent mode ? What time of year should it be used ?
A: Attic flies have a habit of hibernating by sheltering in every nook and cranny of the house. Due to their small size, the attics and attics of houses are easily accessible places for them. They can gather in the hundreds in clusters waiting for the temperatures to rise. When spring arrives, they then seek to go out. They don't always find the exit. This is also why we can find them around the doors and windows of our homes. Loft flies do not cause damage but can be particularly troublesome due to their large numbers.
The adult attic fly feeds on the nectar of flowers, so it is brought out of your home to feed.
You can choose not to eliminate them, but be aware that this insect can reproduce extremely quickly, up to 4 generations per year if the temperatures are high. I advise you to proceed as follows.
It is important to locate the nest and the access points. You can proceed in 2 steps:
First a treatment with our 4J insecticide. It exists in its already diluted and ready-to-use form at 5% (recommended concentration against flies), or in its concentrated form, which will allow you to treat larger areas (up to 200 m²). For the concentrated product, you make the 5% dilution with water in a garden sprayer. Direct spray application to visible flies and accessible crevices. This insecticide is a contact insecticide. For it to work properly, it must therefore be able to bring it into contact with insects (eggs, larvae or adults).
In a second step, you can put in place a repellent to prevent flies from re-establishing themselves in the premises. For this, we have 2 products that will work, with 2 different active ingredients. One is pyrethrum geraniol repellent. It exists as for 4J, either in ready-to-use form, or in concentrated form. Or our Habitat insect repellent made from eucalyptus citriodora. Like 4J, to be applied by spraying on surfaces.
Finally, if you wish, you can use the smoke pyramid or our Habitat fogger. That should eliminate a good chunk of it. Its duration of action remains limited (a few hours) since it is an insecticide. It can be used at any time of the year. The one where the number of flies is the most important being the most effective. Do not forget to condemn the identified access points (as far as possible of course). This will limit their reinstallation.