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. Blow flies love carrion (dead animals) and will find anything dead within minutes of death.
BLOW FLY BIOLOGY ^
Blow flies are naturally attracted to the gases decaying bodies release. Their sole purpose for being is to recycle carrion and once they find the body, blow flies will lay hundreds of eggs.
The larva stage of these flies (MAGGOTS) will feed on the carcass until there is nothing left. The process for the complete consumption of the dead body could take several cycles of the fly, but the larva will pupate and adults will just keep laying eggs until the food supply runs out.
WHAT CAUSES BLOW FLIES TO COME AROUND? ^
Blow flies are mostly attracted to dead bodies, garbage and animal feces. They’re so so outside in the yard, they’re hard to see unless you spy them on a pile of dog feces or dead carcass.
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.
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. But if they are using your home as a place of rest for regrouping post reproduction, you’ll need to do some pheromone removal.
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 summer, blow flies will be actively flying everywhere. But since they’re so hard to see, 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 and high moist temperatures will enable them to prosper. And though these flies don’t bite, they will be a major nuisance in the home.
Now in general, they’ll be most active when its warm. So the summer and fall are when most people find them in the home. This instances can be nothing but chance. But if you find them in the winter, its a sure sign something is luring them to your 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 pyrethrin active which causes flies to “malfunction”. They essentially get paralyzed which causes death within a few minutes.
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. 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, garbage area, dog pen or structure where blow flies are seen accumulating, spraying MAXXTHOR EC will both kill and keep them away for 1-2 months. Maxxthor is fast acting and highly repellent to these flies and works immediately.
For flies, 1 oz per gallon of water and plan on getting 800-1000 sq/ft of coverage per mixed gallon of spray.
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.
Use a good PUMP SPRAYER to apply the Maxxthor and use a wide dispersing “swath” spray pattern when treating.
BLOW FLY BAIT ^
Another “spray” option is actually a bait. It uses a strong fly pheromone flies cannot ignore. So instead of having to spray the entire structure to put a protective barrier in place, using this option will require must less product.
To use MAXFORCE FLY SPOT BAIT, you only need to spray the mixed solution on surfaces close to or where flies are known to be active. The bait contains the lure which will attract them. And once they land on the spray, there is a unique “non repelling” active they cannot detect. They will then pick up a small bit of the chemical and 1-2 days later die.
Add 2 oz per 16 oz of water and spray the diluted mixture over 125 sq/ft. This would be an area slightly larger than 10 ft by 10 ft.
Treatments in a protected area, like under a covered deck or gazebo, will last 3-4 weeks. If applied on the side of a building, you should get 2-3 weeks of control. And when sprayed on the ground, only 1-2 weeks of control.
Another great way to use this product is to apply it a good 1/4 acre from where you’re active and don’t want to see flies. If you’re able to spot treat 3-4 locations around your yard or home, you can essentially divert all fly activity to the bait so you never see any where you spend time.
Once in place, flies will focus on the treatment, land and die 1-2 days later. Within a week, all activity should cease.
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 ^
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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