A gnat infestation in your home is often an indication of a fungal infection, such as those that develop from overwatered houseplants or molding food waste. While you must cure the root of the problem to eliminate the pests altogether, you will probably want to kill the gnats you have in the meantime, to avoid spreading any of the fungus and having to see the nasty little bugs flying around your home. A combination of liquid dish soap, sweet syrup and vinegar will serve as a homemade gnat killer.
Things You'll Need
Apple cider vinegar or syrup
Unscented liquid dish soap
Fill a small bowl or cup three-quarters of the way with apple cider vinegar or sweet syrup. The size of the bowl or cup depends on what you have available and how many gnats you have; you can use any container and you can reuse it later after you clean it.
Add enough unscented liquid dish soap to fill the rest of the container. The sweet smell of the syrup or vinegar is what attracts the gnats, so you have to use unscented dish soap. The soap drowns the gnats with its stickiness.
Place the container in any area where you have seen gnats, such as next to trash cans or houseplants. Use multiple containers if necessary to ensure that you cover all areas where gnats congregate.
Change the mixture out as necessary as gnats begin to die in the container. You should see dead gnats appearing in the mixture within a few days; the amount of time needed to kill all the gnats depends on your infestation.
If you are worried about pets or children getting into your gnat-killing mixture, cover the container with plastic wrap and poke small slits (about an eighth of an inch) into the cover at random places across the plastic. This allows the gnats in but keeps everything else out.