House flies, bottle flies, flesh flies, and more can all get inside structures. They are all known to carry food-borne diseases. They can also carry not just drug resistant bacteria, but multi-drug resistant bacteria. That can mean closures of restaurants, hospitals, food processing facilities, and more. It can mean recalls of food products resulting in lost money from those products and lost revenue from loss of consumer confidence.
One thing we don’t discuss too often is what to do when large flies get indoors. Sure, we’ve got insect light traps but those won’t catch everything and should be used as a monitor more than a control device. We know that dealing with the breeding grounds (almost always outdoors) with sanitation and excluding the flies from getting in is key. The world isn’t perfect and problems do happen and those large flies can get indoors.
So let’s get into when things go “wrong”.
Flies aren’t getting in through solid walls. They access the structure through doors, windows, vents, cracks, and any other opening they can find. Large flies most often land and rest before entering. You can see them resting on door and window frames outside and even during the day some light will be coming from those points, attracting the flies in. The flies are most likely to be on ground floor openings vs upper floors. So those points can be targeted with a liquid residual or an aerosol. This can knock down a huge amount of flies before they can get in.
Inside, they are drawn to food smells and light, sometimes heat. Here are some areas to look for:
Lighted menu boards - this is a big one that flies really like resting on and resting near.
Heat lamps - not just on the outside of the light shade, but all the way up the cord to the ceiling.
Buffet tops, those “sneeze guard” things - (ew, buffets)
Trash bins - you know it's a mess between the can and the liner.
Soda machines - flies love sugar!
Liquor bottles (bar areas) - and flies like alcohol.
The problem with most of these spots is that they are food contact surfaces or near food contact surfaces. Contaminating those with a pesticide is a really bad thing. If a liquid or an aerosol is going to be used, it has to be done very carefully and very targeted to specific areas. Food contact surfaces may need to be covered and/or cleaned to prevent any contamination. There are some products you can make “bait stations”. In one restaurant, we would treat index cards and hang them where we could, out of view of customers. At another location, we treated the hanging heat lamps by covering the counter below them and using an aerosol on the outside of the lamps and up the cords.
The moral of this story, look for the lights and where the light is shining, that is where the majority of adult flies will go to rest. Treat those areas when it is safe to do so, and you may need to get a little creative. If you want to improve your large fly programs, we do that for you, contact us.
Urban pest consulting
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