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University of Minnesota Extension


Quick facts

  • During the summer, flies are attracted to human and animal waste and garbage, so they are sometimes called "filth flies." They can transmit diseases such as diarrhea and dysentery.
  • Other flies can be seen in and around homes during late summer and fall as they look for warm places to hide for the winter. They are a nuisance and don't harm people or property.

Preventing and controlling filth flies

The most effective way to control them is to keep your home and yard clean:

  • Tie plastic garbage bags tightly to reduce odor.
  • Clean garbage cans regularly to remove food and odors.
  • Use garbage cans with tight-fitting lids and place as far away as possible from your home.
  • Remove animal manure, rotting mulch, lawn clippings and dead birds and animals from your yard.
  • Cover compost piles with black plastic sheeting.
  • Use 14- to 16-mesh screen on doors and windows.
  • Once they get inside, a simple flyswatter is effective against small numbers of flies. Sticky flypaper rolls can be used to trap flies and are available at most hardware stores. Hang flypaper out of reach of children and pets.

Life cycle

  • All flies belong to the insect order Diptera, meaning "two-winged." Most other adult insects have four wings.
  • Flies have four life stages: egg, larva, pupa and adult. Eggs are laid in a variety of decaying organic material and hatch into pale, legless maggots.
  • When development is complete, the maggots search for a dry place to pupate. The pupa is the immobile stage characterized by a hard, dark brown shell.
  • The adult flies may emerge in as little as seven to fourteen days.

Using insecticides

Although insecticides are not effective in long-term control, they can be used to temporarily reduce fly numbers.

Treat outdoor surfaces in areas of high fly activity, especially around doors, windows, garbage cans and dog houses, with a residual spray of an EPA-approved insecticide such as permethrin or bifenthrin. Be sure that the product is labeled for the site you intend to treat.

Hiring a licensed pest control operator to treat heavy infestations of flies may be the best approach. Certain insecticides are available only to pest control operators.

Spot-treat large numbers of flies indoors with an aerosol spray labeled for flying insects, such as pyrethrin or tetramethrin. This is a short-term solution and will not solve an ongoing problem.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the area you wish to treat is listed on the label of the pesticide you intend to use. Remember, the label is the law.

Common filth flies


Fall nuisance flies


Authors: Jeffrey Hahn, former Extension entomologist, and Valerie Cervenka, Minnesota Department of Natural Resources

Reviewed in 2024

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