Keeping the potting mix a little drier is often the easiest way to deal with fungus gnats.
Fungus gnats -- small, flying insects often mistaken for fruit flies -- are common houseplant companions. These tiny critters lay eggs in moist potting mix; the eggs hatch and feed on the potting mix; then become adults that lay more eggs.
- The easiest and most straightforward way of dealing with fungus gnats is to allow the top inch or so of the potting mix to dry between waterings.
- Alternatively, you can spread a 1-inch-deep layer of sand over the soil. Sand creates a dry barrier that fungus gnats can't lay their eggs in.
- There is a naturally occurring bacterium you can mix with water and add to the potting mix as you give the plant moisture. This bacterium will build up a population in the potting mix over time and attack the fungus gnat larvae as the eggs hatch.
- Alternatively, there are chemical pesticides available you can mix with water to deliver into the potting mix to get rid of the larvae.