How do I get rid of flies in the house?

Killing adult flies achieves nothing if eggs are hatching somewhere. A sudden large number of flies in one room almost always means a breeding site nearby, and locating it is the whole job.

What you'll need

• Torch
• Bin cleaning materials
• Fly screens (optional)

Step by step

1. Work out which room they concentrate in.Flies stay near their breeding site. The room with the most is where to look, not where you see one or two.
2. Check the bin and the area under it.Including the space beneath the liner where liquid collects. Wash the bin out, not just change the bag — this is the most common source.
3. Check drains and plugholes.Small hovering flies near sinks are usually drain flies breeding in the organic film inside the pipe. Clean the drain rather than the room.
4. Check for forgotten food.Behind appliances, under units, a fallen piece of fruit, a bag of potatoes or onions going off in a cupboard.
5. Check plant pots.Small dark flies around houseplants are fungus gnats breeding in wet compost. Let the soil dry out between waterings and they disappear.
6. Consider a dead animal if there are suddenly many large flies.A mouse or bird in a loft, wall cavity or under floorboards. Follow the smell and the concentration of flies — it will resolve on its own but slowly and unpleasantly.
7. Deal with the source, then remove the adults.Once the breeding site is gone, the remaining flies die off within days. Traps and sprays are a supplement, not a solution.
8. Prevent recurrence.Fly screens on windows, a bin with a proper lid, fruit covered or refrigerated, and drains flushed regularly.

Tips

• Fruit flies breed in a few days in anything fermenting. A trap of cider vinegar with a drop of washing-up liquid catches the adults while you find the source.
• Flies are attracted to warmth and light. Closing internal doors and opening one window on the far side of a room moves them out efficiently.
• Compost bins and food caddies need washing regularly. They are the most common indoor breeding site after the main bin.

Common mistakes

• Spraying insecticide and doing nothing else — It kills adults while eggs continue hatching. The flies return within days and you have sprayed chemicals for nothing.
• Changing the bin bag but not washing the bin — Liquid and residue at the bottom of the bin is where the larvae are. The bag is not the problem.
• Ignoring a sudden large number of flies — It often indicates a dead animal in the structure, which will get considerably worse before it gets better.

Questions people ask