Why fruit flies, cockroaches, drain flies and pantry moths appear, broken down into food, water and shelter, plus how to seal entry points and use pest products safely.
Household pests settle where three things are available: food, water and somewhere to hide. However many you kill, they soon return if those conditions stay the same. So the order is: remove the cause, block the way in, then deal with what's left. Remember too that the one you can see is usually only part of the whole population.
Fruit flies are drawn to ripening fruit and fermenting smells, and they lay their eggs there. They grow from egg to adult quickly, so numbers can jump noticeably within days. That means removing places to lay eggs matters more than swatting the ones in the air. Put ripe fruit in the fridge and seal peel in a bag before throwing it away. Leftover drinks in bottles and cans saved for recycling are prime breeding spots too, so rinse them first.
Once the source is dealt with, a simple trap can mop up the fruit flies that remain. Pour vinegar or fruit juice into a small cup and add a drop or two of washing-up liquid; the detergent breaks the surface tension, so flies that land can't get out. Covering the cup with cling film and poking a few small holes also works. But if the source is still there, a trap alone won't bring numbers down. Tiny flies hovering over pot plants are usually a different kind that breeds in the soil, so watering less and letting the soil dry out works better.
The small, heart-shaped flies that sit around bathroom and kitchen drains breed in the slimy film lining the inside of the drain. Spraying insecticide won't stop them while that film is still there. The key is to scrub the inner walls of the drain with a long brush to strip the film, then flush it with hot water. Pouring boiling water straight in can damage pipes, so water too hot to keep your hand in is enough. Drains that go unused lose the water in their trap, letting flies and smells come up, so pour some water in now and then.
Cockroaches get in through drains, pipe holes under the sink, gaps where gas or air-conditioning pipes pass through walls, and gaps around doors, and they also hitch a ride in delivery boxes. The corrugations in cardboard make good hiding places and can carry egg cases, so it is safer to unpack boxes at the front door and put them straight out. Fill gaps around pipes with silicone or a gap filler, and fit covers or strainers on drains. They are mostly active at night, so seeing them in daytime can mean there are already many.
A spray is fine for killing the one in front of you, but it doesn't reach the hidden colony and its smell can scatter them. Bait works closer to the root of the problem, because roaches that eat it go back to their hiding places and affect others too. Place small amounts in several spots near corners, gaps and anywhere you see droppings that look like black specks. Spraying insecticide near bait makes roaches avoid it, so don't use the two together. Bait dries out and loses its effect over time, so replace it on the schedule shown on the pack.
Small moths or larvae inside bags of rice, flour, nuts or dried fruit are pests that feed on stored food. They can get through thin plastic bags, so move food into airtight containers with tight lids, and keep anything you'll store for a long time in the fridge. Buying smaller amounts more often also helps. If you find them in one bag, throw that food out, check every other bag on the same shelf, then wipe the shelf down thoroughly.
Follow the directions and warnings on the label of any insecticide or bait. Keep products out of reach of children and pets, don't use them near food or dishes, and ventilate after spraying. Fogger-type products need every instruction on the pack followed, including covering smoke alarms, putting out flames and getting people and animals out. Don't mix products. In flats and apartments, units are connected by pipes, so treating one home has limits; if they keep coming back after a few weeks of effort, talk to the building management or call a professional pest control service. If you feel unwell after exposure to a pest product, contact a medical professional straight away.
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