In Marin, flies are often a nuisance during summer and fall, and some species enter our homes. Here are the most common:
Filth-breeding flies like house flies and blow flies develop in compost, animal waste, dead animals, and garbage. These flies are commonly contaminated with bacteria, including those associated with food poisoning and can spread disease when landing on food.
Fruit flies, also called vinegar flies, lay their eggs in overripe, rotting fruit. As adults, these small flies are commonly seen flying around open areas where ripe fruit is stored.
Drain flies, also called moth flies and sewer flies, live in sink and sewer drains in their larval stage. The adult female flies lay eggs on the slimy organic matter that builds up inside drains where the larvae then feed.
Fungus gnats develop in soil as larvae. They can be found indoors breeding in potting media used for houseplants or hovering near windows.
The best way to manage flies and prevent future infestations is to focus on exclusion, sanitation practices, and habitat modification that removes fly breeding sites and attractive conditions.
- Remove or cover garbage and clean up spilled animal feed, manure, and pet waste.
- Remove and dispose of overripe fruit that is attracting fruit flies. Wash the area with soapy water.
- Manage drain flies by removing the organic matter in drains with a hard bristle brush.
- Let the soil surface of potted plants dry out between waterings or water plants from the bottom using saucers to remove the attractant for fungus gnats – overly moist potting soil.
- Indoor fly problems can be managed by keeping them out with screening and other exclusion techniques. Caulk, screen, or cover all small openings into a home to prevent flies from entering.
Traps can also be effective. Fly paper and electrocution light traps can kill flies but are effective only in areas where exclusion and sanitation efforts have already reduced the fly populations to low numbers. Single flies can be easily killed with a flyswatter. Various food-based traps are also available. These traps often contain a protein or sugar-based bait, sometimes with the addition of a fly pheromone (sex attractant). These traps are effective for species that breed on dead animals and garbage, such as blow flies and house flies and should be placed near the highest concentration of flies.