house fly

The Vector Control Program provides educational fly consultations to County residents. The Vector Control Program is not a pest control company and does not trap, bait, or remove flies. 

Most types of flies in San Diego County are nuisance pests. Rarely, some have the potential to cause allergic reactions, contaminate food, or spread disease.   

In some regions of the U.S. and around the world, flies can cause more serious diseases, but almost all reported cases of these infections in San Diego County were contracted while visiting other countries.


  • House Fly (Summer): This fly is the most frequent pest to humans. The common house fly is grayish-black, about 1/4-inch-long, and covered in hair. In two weeks, one female fly may lay more than 1,000 eggs, typically in animal waste, household garbage, piled lawn clippings, or rotting fruit and vegetables.
  • Lesser House Fly (Cooler weather): The lesser house fly is seen flying around at eye level, hovering in the middle of a room, in a garage, on a patio, and under trees or other covered areas.  Larvae develop from eggs laid in moist organic matter.



Attractants are things that draw flies to your property. These include dog poop, trash, or anything with a strong smell. Removing attractants will help reduce flies. 


  • Cover garbage: Flies like to breed in the "muck" often found at the bottom of garbage cans. Clean garbage cans regularly and keep lids on tight.
  • Dry manure: Wet manure attracts flies. Keep manure piles dry, flat, or covered. Dog poop may attract flies and should be removed, but typically is not responsible for fly breeding as it dries quickly.
  • Dry grass clippings, straw or hay: get rid of clippings quickly or make sure they stay dry.
  • Cover compost piles: Wet, decaying matter attracts flies. Make sure to keep compost piles tightly covered.

If you have dumpsters, it may be necessary to have trash picked up twice a week, especially at restaurants and apartment/condo complexes where there is a lot of trash.

Exclusion and Control


To keep out flies out of your home:

  • Screen doors and windows with at least 16-gauge mesh.
  • For small flies, such as fruit flies, use 24-gauge mesh.
  • Keep screens for windows and doors in good repair and free of gaps or holes.  

Businesses may also want to:

  • Install self-closing doors.
  • Install high-velocity fans over doors that must remain open.


Other control methods are generally not as effective as removing breeding sources, but may help.

  • Fly strips are easy to use and can be placed around the home to help catch flies. Fly strips can be purchased at most grocery or home improvement stores.
  • If using fly traps with fly attractant lures, place them around the perimeter of the property, away from where people spend time, so as not to draw flies towards people.
  • Fly swatters are effective for occasional flies.
  • If insecticides are used, be sure to follow the instructions carefully.


Knowing the type of fly on your property can help to identify its breeding source. You can submit a fly sample to the Vector Control Program for identification.  


  (858) 694-2888


house fly photo by Axel Rouvin