Blow flies thrive primarily on dead bodies of small animals such as rodents. They are easy to identify because they are medium to large in size and have a metallic glare on their body. They come in several colors including blue, green or yellow. They fly well and can reproduce in manure if unable to find a dead animal on which to lay eggs.
Related articles: DRAIN FLY FRUIT FLIES FUNGUS FLY GNATS
Blow flies are one of the more common fly species active during the warm months of summer. This article will explain why they come around, what they’re looking for and what you must do to reduce their number.
One of the easiest way to see a blow fly is to look in the yard or street for a dead animal or other organic, decaying matter. They’ll thrive in moist soil as material like pine straw, wood chips, moss or algae break down.
Blow flies love carrion (dead animals) too and will find anything dead within minutes of death; their eggs will hatch larvae which eat the animal and then crawl off to the ground and surrouding landscape to molt into adults.
BLOW FLY BIOLOGY ^
Blow flies are naturally attracted to the gases decaying bodies and other decaying matter. Their sole purpose for being is to recycle carrion and plants and once they find a good food source, blow flies will lay hundreds of eggs.
The larva stage of these flies (MAGGOTS) will feed on the carcass or dead plants until there is nothing left. The process for the complete consumption of the food can take several cycles of the fly, but the larva will pupate to adults quickly keeping the supply of maggots fresh and aggressive.
WHAT CAUSES BLOW FLIES TO COME AROUND? ^
Blow flies are mostly attracted to dead bodies, garbage, decaying plants and animal feces. They’re generally found outside in the yard so they’re easy to find if you look carefully. They love living under cement slabs like patios, driveways and walkways – especially where water runs into cracks and gaps. Under the cement will be large organic “pool” of food as the matter breaks down and decays.
In the home, they’ll fly from window to window trying to get out.
In the winter, blow flies can still be active as long as they smell food. Common food for them when its cold include road kill and dead rodents in homes which seem to be more available when its cold. This probably happens because people tend to use rodenticide in the winter. Rodenticide will almost always lead to some animals dying in the attic or wall. And even though these spaces might be “inside” the home, rest assured fumes are releasing to your attic and eventually outside. From there, the odor will quickly call in blow flies from the neighborhood. And this can happen even in the dead of winter.
BLOW FLY PHEROMONE CONTROL ^
Lastly, blow flies will gravitate toward any home that has been “marked” as a place for them to congregate post reproductive cycle. This “regrouping” time is when they seek a safe refuge to rest and relax. Over the course of an adults life, they can cycle through several reproductive encounters and will hold up in structures, mulch or tree trunks to recoup.
If your home has been designated as such a site, it will have a never ending flow of blow flies during the summer and fall as they seek a comfortable place to rest and relax. This will lead them to living spaces and in some cases, be a bit overwhelming depending on local populations.
So if your home has been “marked” as a safe place of refuge, don’t expect to find any “source” or reason for them to be present. The fact is they’re only responding to the fly pheromones that have been left on your homes siding, roof line, vents, etc. This pheromone is very strong and will attract flies for miles.
To deal with the occasional invader or if you had a very specific source in or around the home that led them to migrate inside your house, scroll down below to see the treatment options we have to kill them off. No doubt exterior treatments with our MAXXTHOR will keep them off the home and you’ll need to use it if you have a lot of fly activity.
But if you’re not seeing a lot, just 1-2 a week and wondering why they keep coming around, they’re probably using your home as a place of rest for regrouping post reproduction. For these types of problems, removing the pheromones will really help keep them away.
This can be accomplished by spraying the homes exterior with our TOTAL ODOR NEUTRALIZER. This agent works on animal and insect pheromones and essentially breaks down the scent at a molecular level. When sprayed on the homes siding and all points of entry, the smell that is attracting them will be removed. Once gone, your home won’t be a beacon calling out to the local blow flies in the neighborhood.
Treatments will work immediately and can be done anytime. Mix 2-4 oz of TON per gallon of water and plan on using a mixed gallon for every 500-800 sq/ft of exterior siding. Be sure to spray up to the gutters soaking them, vents, around windows, etc. so you can eliminate all lingering pheromones.
WHEN IS BLOW FLY SEASON? ^
Blow flies can appear any time of year. Most common in the spring through fall, blow flies will be actively flying everywhere. But since they’re so hard to see while flying, you have no idea how many are around in the yard.
During the winter, they won’t go outside unless they catch a scent luring them to investigate. Road kill, manure, potted plants and high moist temperatures will enable them to prosper and in general, any of these scents can be present in the average home. And though these flies don’t bite, they will be a major nuisance in the home.
The bottom line is if you find one blow fly in the winter and don’t see anymore for a week or longer, it was probably just an isolated event. But if you’re seeing more than 1 a day, you have a problem which needs to be addressed.
HOW TO TREAT A BLOW FLY INFESTATION ^
The best way to treat active blow flies will depend on where you’re seeing activity, what is luring them to the home and where they’re active. In some cases they’ll be seen randomly flying around. These problems will require aerosols applied to “take away” their air space. Flying insects need good air to fly and even the slightest amount of product applied to a controlled volume of air like that in a structure can make it impossible for them to move about.
In other cases, they’ll be seen landing on the home, garbage area or maybe in the yard. These problems will be easier to control using a spray.
Lastly, baiting or trapping will always help and though not considered to be a “true” control, these options will help keep ongoing fly problems minimized.
BLOW FLY INSIDE SPRAY ^
For blow flies randomly flying around inside a structure, a good space spray like MULTIPURPOSE INSECT KILLER will stop their activity. Multipurpose uses a strong permethrin active which causes flies to “malfunction”. They essentially get paralyzed which causes death within a few minutes.
The following “short video” (less than 60 seconds) will show how to use the Multipurpose in the home along with the Aerosol Machine setup. Both will control flies immediately; the Aerosol Machines do so automatically making them a good solution for many people looking to save time and avoid relapse infestations.
Multipurpose should be sprayed in the middle of rooms for 5-10 seconds where flies are active. I will move around and flies moving through the treated air will die.
Multipurpose is safe for use around people so you can re-enter treated rooms within 10 minutes after they’re sprayed. But one of the drawbacks of its safety is that it won’t last long. This means you should plan on using it as needed. If flies come back 2-3 times a day, spray that often. By killing the adults, you will be ending the egg laying so eventually, the problem will end. But it could take 1-2 weeks of persistent treatments.
One can is enough to treat the average 2500 sq/ft structure 3-5 times so plan on using a can a week.
For a more “permanent” solution, install AEROSOL MACHINES. These are small devices which run on 2 “c” cell batteries. Set to go off every 15 minutes, they’ll release a 1/2 second dose of insecticide so that over time, the treated rooms will have in place an ever active amount of pyrethrin effectively taking away all the air flies need to live.
The amount released is so subtle you won’t know anything is being applied. But it will be strong enough to control pests like noseeums, gnats, mosquitoes, moths and flies.
Machines should be mounted 6-8 feet up off the ground on a wall but you can also set them on wall units or countertops.
Each machine will cover 400-500 sq/ft and will need one of the refills listed below.
In each machine you’ll need a can of CLEAR ZONE. This odorless pyrethrin based aerosol works like Multipurpose in that it will make a fly loose its ability to move and eventually die. Cans will work for 30 days in the machine above so plan on replacing them monthly. In general, it will take 2-4 weeks for most problems to be eliminated in structures so plan on using the machine for at least one month. For ongoing problems, plan on replacing the can on a regular basis during the warm season.
BLOWFLIES COMING FROM DRAIN
If you’ve noticed the flies hanging around your drain, like the kitchen sink, work sink or shower, you could very well have them living in the drain or sewer system. Homes which have Septic tanks are most prone to this issue.
From the sewer line or septic tanks, larvae will crawl up and into your drain line. Once they pupate and become adults, they will end up filtering up through sink drains and from there, fly throughout the home.
The following “short video” (less than 60 seconds long) details how to use this product in your sink, tub or shower to control any pest that might be living down the drain.
Unlike most flying pests, blowflies will not fly back to good nest sites. So identifying the drain as the likely spot of origin can be tough.
But if notice just one fly in the sink or coming out of the sink, that’s really the only clue you’ll need to start treating it with LEMON AIR.
This product is the only option available for down the drain that’s actually a pesticide. It smells like lemons and will help control most any insect including roaches, ants, flies, crickets and more.
Add 2 oz per gallon of water and plan on treating once a week during the spring and summer months. Using Lemon Air on a regular basis will help keep the drain smelling nice and it will control any pest that might want to move in during these months.
LIQUID FLY SPRAY FOR OUTSIDE ^
For the yard, barn, stable, under concrete slabs like patios or pool decks, in garbage areas, dog pen or structures where blow flies are seen accumulating, spraying MAXXTHOR EC will both kill and keep them away for several weeks. When applied under a slab, it will control them for many years.
Maxxthor is fast acting and highly repellent to flies and works immediately.
For flies, 1/2 oz per gallon of water and plan on getting about 1000 sq/ft of coverage per mixed gallon of spray.
The following “short video” (less than 60 seconds long) shows how to prepare our hose end sprayer to make treatments to the side of the home, turf and mulch.
Maxxthor should be used on the ground, shrubs, home siding and basically anywhere flies are landing. Apply it using one of the sprayers we have listed below.
The BEST HOSE END SPRAYER for this task is our green topped 20 gallon model (featured in the video above).
BLOWFLY TREATMENTS FOR UNDER PATIO SLABS AND POOL DECKING ^
Blowflies can also thrive under pool decking, patio slabs, driveways or any cement slab attached to a home.
You see, the bottom side of any cement slab is a sponge that collects moisture. Mold and algae will readily grow there and pests like Flies will readily migrate down to this decomposing organic matter to lay eggs.
Once they move in under the cement, it can be near to impossible to reach them with Maxxthor.
So if you’ve seen flies coming from gaps, cracks or joints in cement sidewalks or driveways, be sure to fill them all with Maxxthor. The following short video shows how to do this.
Now if you’ve tried and found you’re not able to get enough product through the gaps and cracks, you’ll need to consider the next step. This involves drilling holes every 24 inches through the cement and then pumping the MAXXTHOR EC under the slab.
To get the holes drilled, use a good HAMMER DRILL and if you get our SUB SLAB INJECTOR, you’ll need to drill with the 1/2″ bit.
Space them 2 feet apart; the slab injector will pump out sideways a good 1-2 feet thus insuring complete coverage.
Our Hammer Drill comes with several bits and the 1/2″ by 8″ long bit is the most common one needed. The average slab will be about 4″ thick but can be thicker.
Drilling might sound like a lot of work but with this drill, its not hard. We’ll be posting a video shortly to show how it cuts through cement so most anyone can make the needed holes. Hammer Drills should be available from any local tool rental shop if you don’t want to purchase one.
Once you’ve got the holes all drilled, treat them with our Sub Slab Sprayer.
This sprayer functions just like our Pump Sprayer but has been modded to spray “sideways” instead of straight out. Here’s a zoomed in shot of the sprayers nozzle (this picture shows a “used” unit that’s been afield):
Once pressurized, the sprayer will project the mixture a good 1-2 feet sideways so you can fill the gap under the concrete where the dirt has settled.
The best way to use the injector is to slowly push the rod into the slab and try to “feel” the soil underneath. Once you can feel the dirt, lift back up 1-2 inches and spray for 5-10 seconds per hole. If you sense the gap underneath is significant, be sure to “back out” the wand so the spray is sure to hit the bottom side of the slab.
Over time the dirt under any slab will settle. This will be at least an inch but sometimes more. The gap will let in moisture and then mold or algae which is food for most any insect and certainly for flies.
Filling the void with Maxxthor will kill all nesting pests and last for several years. Mix the Maxxthor 1 oz per gallon to insure you’re getting 5+ years of residual.
HOW TO TREAT BLOW FLIES UNDER EXTERIOR SIDING ^
Since blowflies will often use a homes siding to “rest” or gather heat, they can work their way into the gaps or voids and start to nest.
This is particularly true for siding like wood shakes, vinyl, stucco or aluminum. Homes with this type of siding will often hold moisture which in turn can grow mold, algae and other organic life forms blowfly maggots need.
Maxxthor sprayed on brick or even masonite will do a good job of keeping it blowfly free. But siding like Vinyl, Wood Shakes Stucco or Aluminum will need to be dusted.
The following short video talks about how to dust your homes siding.
If you’re seeing blowflies active on or “in” the homes exterior siding, they’ll be nesting in the void. This will require a good dusting.
The best product for these areas will be DELTAMETHRIN DUST. This dust is like “baby powder” but its moisture resistant and can be “puffed” up and into all the gaps and voids. Dusting will last 6-12 months and if you do a good soil treatment with the granules and liquid spray, you may not have to treat these areas again.
Use Deltamethrin Dust at the rate of 1 lb for every 1,000 sq/ft of siding.
Apply the dust with a good HAND DUSTER.
If you need to dust row after row of vinyl siding, cedar shakes or some other exterior siding blowflies are using, consider getting a DUSTICK. This tool will let you do the dusting from the ground without having to climb a ladder.
Our Dustick features 4 extensions, each 4 feet long, which can be used one at a time or slid over one another to create a tool 8 feet long, 12 feet long, 16 foot long and longer if needed. Combined with the dust canister on top and the pump assembly on the bottom, you will be able to treat locations up to 25 feet high while standing on the ground and you can purchase extra 4 foot extensions to make it even longer.
This short video (less than 1 minute long) gives a good overview of how the Dustick works and why its essential for homes with blowflies living under the exterior siding.
When you have a lot of siding and trim to treat where blowflies might be nesting, Deltamethrin dust is longest lasting formulation for the job. And since it will control other pests too, it’s your best bet for long term control on home siding.
BLOW FLY TRAPS ^
FLIES BE GONE FLY TRAPS traps are another option that can really help managing flies too. Like the bait, they use strong pheromones flies cannot ignore. As flies get close to the trap, they’ll detect the smell, find the trap, enter and be trapped inside.
These traps work by releasing strong smells so they should be used away from people and public areas. This way the flies are lured away and won’t be bothersome when approaching the trap.
As traps fill, they become more effective. Eventually though they will fill and should be discarded when there is no room left inside.
Use 1 trap per 1/4 acre.
CONTACT US ^
Give us a call if you need further help. Our toll free is 1-800-877-7290 and we’re open Monday through Thursday, 9:00 AM to 4:00 PM. On Friday, 9:00 AM to 4:00 PM and on Saturday, 9:00 AM to 2:00 PM (Eastern Standard Time).
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Linda says
How can flies be getting into a room when the doors and windows remain closed? Can they come through the carpet?
Tech Support says
It’s not likely they’re coming from outside the room where you see them. In fact, its most likely they’re coming from something in the room. You see, it only takes one fly laying eggs to fill any average sized room with adult flies. Since she can lay hundreds of eggs, as long as the hatching larvae have something to eat they will rapidly develop into adults and start appearing like you’ve been seeing.
Now how to best control the population is to treat where the eggs may have been laid. Since carpets will many times harbor all kinds of food (as can couches, sofa’s, etc.), treating these areas with some Permethrin 10 would be a great way to start. It’s odorless and will quickly kill developing larvae. Within a few days of spraying the area, the problem will be greatly reduced and by a week, should be gone if this is where they were originating.
But if you’re not 100% sure they’re coming from the carpet, go with a space spray instead. PT-565 can be applied as often as you’d like to the air in the room. It will only take 3-5 seconds to treat the area and if you did this in the morning and evening, you should be able to kill any that appear in the room.
Lastly, a more permanent solution would be to set up an aerosol machine with some Purge III. It too used pyrethrin as its active but instead of you having to manually control the application, you can set the machines to go off every hour or so. This way you’ll constantly have a new application being done to the room which will control any flies that choose to enter. Refills last a month or more so its a cost effective way to treat these types of problems and very easy too.
Here are links to these items in our cart. Please show your support for our business by purchasing the items we recommend from the links provided. Remember, this is the only way we can stay around and be here to answer your questions and keep this valuable web site up and running. Thanks for your business!
PT-565: https://bugspray.com/catalog/insecticide/aerosol/pt-565-xlo
Aerosol 2000: https://bugspray.com/equipment/foggers/aerosol-dispenser-2000
Purge: https://bugspray.com/catalog/insecticide/aerosol/purge-iii-6-25-oz.html
Erika Smock says
My neighbor noticed this morning about 30+ blow flies along the baseboard of her living room. Her apartment is clean, I clean it and no one except her and I come and go. The only thing I can think is that the storage unit on the other side of the wall had some rotten meat in it a week ago. Is it possible for them to come through the wall? The building is old… and the maintenance guy says he washed out the storage unit with bleach. I just find it strange that the flies are all lined along the wall on the floor along the same wall as the storage unit.
Tech Support says
Erika,
I do not see a question anywhere so I’m not sure how I can help.
What I can tell you is that all flies are insects. And like any insect, they lay eggs. In this case, I’m 100% sure you have hatching fly pupae in this apartment where they are being seen. Insects start from eggs, become larvae then pupate to become adults.
What I also know is that pretty much every day I field emails and talk to customers who have flies in the home, yard, etc. so given its summertime, what you’re experiencing is not strange at all; in fact its quite normal.
What I also know is that like any other insect problem, it will either pass, stay the same or get worse.
Lastly, I also know using our MultipurposeAerosol (seen above) or setting up some of our aerosol machines will kill any flying pest in this apartment so they can no longer lay eggs. Remember, the adults do one thing: mate and lay eggs. And like any other insect, failure to kill off the adults and allowing them free access to your apartment will generally allow for them to continue to be a problem.
Technical Support
1-800-877-7290
PS: Are you signed up for our informative twice a month Pest Report Newsletter? More info here: https://bugspray.com/bugspray_pest_report.html
Jake says
Hi there,
For the past 3-4 days, we’ve had a blowfly infestation. There have been at least 50+ blowflies in our backyard. They’re mainly sticking to the garden floor, barely leaving the grass. I don’t know what else to do to prevent them from sticking around. So far I’m doing the following:
– Regularly cleaning up dog poo, normally within an hour of it happening.
– Double-bagging garbage and dog poo in a tight lid bin.
– Laying down two fly traps which are working great, but they haven’t necessarily
stopped the flies from returning in great numbers.
I was wondering what you would suggest? I’m also wondering if you could help explain why they’re sticking to the garden floor when there is barely any trace of dog poo. I can’t see any rotting meat nearby nor any carcasses.
Tech Support says
Jake,
If you look above in our article, you’ll see what you need. The best option is the Maxxthor. Mix up 1 oz per gallon of water and spray it everywhere. It will kill off all active flies and keep them away.
Next, set up some of our Fly Bag Traps at the back edge of your property. They will help by collecting rogue flies before they find areas closer to your home.
Technical Support
800-877-7290
PS: Are you signed up for our informative twice a month Pest Report Newsletter? More info here: https://bugspray.com/bugspray_pest_report.html
Kory says
Hello,
We’ve been dealing with a strange blow fly problem for a few years now with no solution. During the summer months, each day we’ll have a few green blow flies buzzing around in the kitchen/dining area of our house. Exterminators have told us that it doesn’t seem to be a source inside the house, as we would see many more flies concentrated in the area and they would have consumed the source by now (we’re on summer #3 of the same issue). Our initial belief was perhaps they were entering at the windows, however they are sealed tightly and I never see them in the sills when we keep the windows closed. Regardless we had the exterminators treat all windows, we have cleaned our air ducts and sewer lines, and sanitized all surfaces and potential sources repetitively, yet still see them each day. Is there any other source that would provide only a few flies, every day for years? Would any of the products listed help us fix the problem permanently? Thanks!
Tech Support says
Kory,
There are so many ways for insects to enter a home, I don’t have enough time to list them all here so the “source” is simple. Its either something in the home (highly unlikely) or they’re coming in from outside (99.99% likely).
Second, if you want them gone, just set up one of our aerosol machines in any room where they’re active. These will kill all flying insects and within a day, you won’t have any more. Details are above..
https://bugspray.com/blow-fly-control.html#blow-fly-inside-spray