Fruit flies and drain flies

Most tiny, slow flies in a kitchen or bathroom are fruit flies, drain flies or fungus gnats. They look alike, but each breeds somewhere different, so it matters which one you have.

• Fruit flies are about 1/8 inch long, tan to reddish brown, with bright red eyes. They gather around ripe or rotting fruit and anything that smells of yeast or vinegar, such as juice and soda.
• Drain flies, also called moth flies, are fuzzy, dark gray to black and look like tiny moths. They rest on the walls near sinks and tubs by day and hover around the drains in the evening. They don't bite.
• Fungus gnats are black and not fuzzy, and they breed in houseplant soil. Gnats, mealybugs and spider mites on houseplants covers them.

What you need

• A clear plastic cup and a sticky card or glue board
• A stiff, long-handled drain brush
• An enzyme drain cleaner, if you can find one
• Trash bags

Steps

1. 1

   Find out where they're coming from

   Tape a sticky card inside a clear plastic cup and set it upside down over the drain overnight. Flies stuck in the cup came up from the drain.

   5 min

2. 2

   Get rid of what fruit flies breed in

   Throw out overripe fruit, peelings and old vegetables. Cover ripening fruit, or keep it in a bag. Rinse cans, bottles and jars before they go in the recycling, and clean the trash can and keep its lid shut.

   15 min

3. 3

   Clean up spills and food bits

   Wipe the counters and the sink, and store mops head up so they dry.

   10 min

4. 4

   Scrub the drain

   Drain fly larvae live in the slimy film that builds up inside drains and overflow pipes. Scrub it out with a stiff, long-handled brush, or use an enzyme cleaner made to break that film down. Bleach doesn't remove it, and the larvae survive bleach well.

   30 min

5. 5

   Flush the drains and overflows

   Run hot water through the drain and down the sink's overflow opening, a common place for larvae to grow.

   5 min

6. 6

   Look for other wet spots

   Check for wet lint under the washing machine and standing water in saucers under houseplants, and fix any leaks.

   5 min

7. 7

   Check the cup trap again

   Set it back over the drain overnight. No flies in the cup means none are coming from that drain.

   1 min

What doesn't work

• Bleach. It doesn't clear the film from the pipes. Never pour bleach after a caustic or lye drain cleaner, since the two can release chlorine gas in the line.
• Insecticide down the drain. No insecticide is registered for use in drains, and pouring one in can damage the sewer system.
• Flying-insect sprays and bug bombs. They kill only the flies in the air. New ones keep coming as long as the larvae are there.
• Sticky strips and light traps. They catch some flies, but they won't end the problem.

Keeping them away

Fruit flies can come in on produce, so keep ripening fruit covered or bagged, especially in summer. Drains that are seldom used, such as a guest bathroom sink or a basement floor drain, are where drain flies start. Run hot water through them now and then.