How to get rid of house flies

These are not fruit flies

A house fly is five to eight millimeters, fast, and lands on food, surfaces and people. A fruit fly is two to three millimeters and hovers around fruit and bins.

The difference matters because almost nothing transfers between them:

• A vinegar lure does not work on house flies. They are not tracking fermentation the way a fruit fly is.
• House flies breed outdoors, in animal waste, garbage and decaying matter — not in your drain.
• Exclusion matters far more, because they are coming in through an opening rather than emerging from inside.

If the insects are tiny and clustered around your fruit bowl, you want how to get rid of fruit flies instead.

Step 1 — find the outdoor source

House flies go from egg to adult in about a week in warm weather and a female lays hundreds of eggs. A single source close to the house produces a continuous supply.

Check, in rough order:

1. Trash cans. The base, the lid seals, and any liquid in the bottom. Bagged waste left beside the can rather than in it.
2. Pet waste in the yard. This is a major producer and it is usually the answer where there is a dog.
3. Compost with cooked food, meat or dairy in it.
4. A dead animal. Under decking, in a wall void, in the roof space, or in the yard. A sudden large number of flies in one room with no obvious source is the classic sign, and it is worth taking seriously.
5. Chicken, rabbit or livestock bedding, which is a textbook fly nursery.
6. Fallen fruit under a tree.
7. A blocked gutter or a drain holding organic sludge.
8. A neighbor's version of any of the above, which you can only ask about.

Step 2 — deal with it

• Bins with tight lids, washed out occasionally, kept away from doors.
• Pet waste picked up daily and bagged.
• Compost turned, kept balanced, no meat or cooked food.
• A dead animal removed — and if it is inside a structure and you cannot reach it, that is a professional job.
• Bedding changed frequently in any animal housing.

Removing the source is the step that ends it. Everything below manages the flies that already exist.

Step 3 — close the ways in

• Window and door screens intact, with no tears, and fitted tightly.
• Door sweeps on exterior doors. The gap under a door is the commonest route.
• Gaps around pipes, vents and utility entries sealed.
• Keep the door shut in fly season, which is obvious and still the main failure.
• A screen door if you want to leave the main door open.

Step 4 — trap what is already inside

Indoors:

• A plug-in light trap with a sticky cartridge is the quiet, tidy option. No zap, no debris, no smell — good for a kitchen.
• An electric swatter. For one or two flies it is simply the fastest thing, and more satisfying than it ought to be.
• Old-fashioned fly paper works and looks like what it is.
• Not a bug zapper indoors. Noisy, and it flings insect debris. Why zappers are the wrong tool for most things.
• Not an aerosol over food preparation surfaces, for obvious reasons.

Outdoors:

• A disposable bait bag hung at least thirty feet from the door you use, and preferably downwind. These work by smelling genuinely foul, and the smell is the mechanism. Hang one by the back door and you have concentrated the flies exactly where you did not want them.
• Sticky fly tape in a barn, shed or garage.
• Fans. A fly cannot make headway in moving air, which is why a fan over a doorway is standard in commercial kitchens and works surprisingly well on a patio.

A note on numbers

A handful of flies is an entry problem: check the screens and the door sweep.

Dozens of flies appearing suddenly in one room is a different signal. That usually means something has died inside a wall, a floor void or a roof space, and the flies are emerging from it. Cluster flies are the other possibility in spring and fall — they overwinter in wall voids and emerge on warm days, do not breed indoors, and are best handled with a vacuum and a light trap.

Keeping them out next summer

• Bins away from doors, lidded, and washed occasionally.
• Pet waste picked up daily.
• Screens checked in spring before the season.
• Door sweeps replaced when they perish.
• Fruit bowls covered in hot weather.
• A fan over the patio door if you like it open.

If the small flies inside turn out to be hovering around fruit rather than landing on surfaces, revisit the identification: gnats vs fruit flies vs drain flies.