How to Get Rid of Small Black Flies in the House
When small black flies invade your home or business it’s not only annoying, but potentially hazardous to your health. Small black flies have the potential to vector human disease. Plus, they make people uncomfortable: Flies are associated with filth.
What are the small black flies in my house?
Four species of small black flies commonly invade homes and business and can be found buzzing around your kitchen, bathroom and house plants. These are fruit flies, drain flies (see above picture), phorid flies and fungus gnats. Each has different habits, behaviours and preferred living conditions.
How do I get rid of small black flies indoors?
To get rid of small black flies indoors, you need to know the type of fly, why they’re present, and where they breed. Killing adult flies won’t solve the problem; you also need to eliminate the breeding site – where eggs are laid, and where fly larvae live -- or new flies will continue to emerge and cause problems. As such, bug spray alone is not an effective, long-term solution to control small black flies indoors.
FRUIT FLIES
How to identify fruit flies - Fruit flies are about 3 mm long. They are attracted to materials in the early stage of decay and fermentation, such as over-ripe fruit and vegetables and spilled alcohol, juice and soda. The flies typically are found in kitchens, food prep and food storage areas, near recycling bins for beverage containers, and damp, sour mops and rags. Fruit flies hover when they fly and have red - or dark-coloured eyes. They enter buildings through open windows (including screened windows) and come in on produce either as adult flies, larvae or eggs.
How to get rid of fruit flies – The fastest way to get rid of fruit flies is to remove the rotting or fermenting items that attract them, such as the soft bananas on the counter or the rotten onion in the cupboard. In commercial kitchens, fruit flies lay eggs in fermenting syrup from a leaking soda line, a lime wedge shoved behind the bar, dirty trash bins, and the decaying organic matter and mop water that collects in the gaps where grout is missing in the tile floor.
Find the breeding site and deep clean it to kill and remove fruit fly eggs, larva and pupae. Clean out and wipe down cabinets with disinfectant. In commercial kitchens, use a putty knife to scrape gunk (and larvae) out of cracks and use fans to dry floors after mopping. Use an microbe-based cleaner on floors to reduce the gunk in which the flies breed. Glue boards, fruit fly traps, flying insect traps and fly lights are the best way to kill adult fruit flies. Some traps must be filled with liquid flying insect bait.
DRAIN FLIES
How to identify drain flies – Drain flies are 2 mm long and look very different than fruit flies. They have long, feathery antenna and a fuzzy appearance. As such, they’re also called moth flies. These flies breed in the mucky film that collects in floor, tub and sink drains, from which they may suddenly appear, sometimes by the thousands. They also may breed under appliances where organic material decays in leaking water. Drain flies are lazy fliers; their flights are short and jerky and you’ll often see them crawling on surfaces near their breeding site.
How to get rid of drain flies – The most effective way to get rid of drain flies is to clean out the drains where they lay eggs. This is a dirty job so wear personal protective gear. Scoop out gunk and scrub out the drain with a stiff brush. Regularly apply an enzyme - or bacteria-based drain cleaner, which eats away the filmy muck in which drain fly larvae live. Chemical drain cleaners will not clean drains well enough to eradicate the fly larvae.
PHORID FLIES
How to identify phorid flies – Phorid flies are 0.5 to 6 mm long. They range in colour from tan to black and they have a humped back. Phorid flies prefer advanced decay, such as dead animal carcasses and waste leaking from broken sewer lines. They also like the sludge found in garbage disposals, garbage bins and drains. At such, they’re easily misidentified as drain flies. Phorid flies reproduce rapidly, and an infestation can have up to a million flies. Phorid flies tend to skip before they fly. They run on a surface, halt, run again, then take flight.
How to get rid of phorid flies – Inspect basements, crawlspaces and near foundations for the odour of leaking sewer pipes. Hire a plumber to fix any leaks; then, remove waste-contaminated soil or rocks. Cover drains with glue boards (sticky side down) overnight and if you find flies stuck in the adhesive in the morning, use an enzyme- or bacteria-based cleaner to rid the drain of sludge where the flies lay their eggs. Inspect for dead animal carcasses in and around the property and remove them wearing personal protective gear.
FUNGUS GNATS
How to identify fungus gnats – Fungus gnats are 1 to 3 mm long, have long wings and spindly legs. They are attracted to the decaying organic material found in the soil of potted plants. Overwatering causes fungi to grow in the soil and this is what gnat larvae feed upon. You also can get gnats indoors when you bring in potted plants or soil from outside. Fungus gnats are attracted to light, like most small flies, so you may see them at windows near infested plants or near TV or computer screens at night.
How to get rid of fungus gnats – Getting rid of fungus gnats starts with finding the guilty houseplant. The quickest remedy is to throw out the plant. If that’s not an option, let soil in the pot dry thoroughly before the next watering. Rake the soil to help dehydrate gnat larvae, which live in the top 2 to 3 inches of soil. In atriums, use fans to help dry soil.
When gnat infestations are severe, excavate the top few inches of soil in the pot and replace it with new, dry soil. Only repot plants with pasteurized soil that was stored indoors. Beneficial bacteria (Bacillus thuringiensis), nematodes, and insecticidal soap applied to soil help control fungus gnats. Cut glue boards and insect sticky traps to size and insert them in the pot to catch adult gnats. Light traps are effective at killing adult fungus gnats in atriums and buildings with large planters.
Read about other flying insects that cause problems indoors:
How to Get Rid of Moths in the House
