Fungus gnats can be a real nuisance when they invade your home. Most of the time they feed off of fungus sitting in the growing medium but they can feed on the roots of your plant, which may eventually kill it. Getting rid of the gnats and their larvae takes some diligence as the adults are replaced every few days. There are various means to rid your plants of these tiny pests, including some ways without the use of pesticides.
Allow the soil to dry out between watering to at least 2 inches below the surface. Most of the gnat larvae will be within this area and will die due to lack of moisture.
Keep the soil free of fallen debris from the plant, such as dead leaves or branches. Pull all weeds and discard away from the plants. As this debris sits on the soil's surface and starts to decay, it will attract the adult gnats for a breeding ground.
Discard all potting medium the plant is currently in and rinse off the roots. Re-pot the plant in new, sterile potting soil.
Place Gnat Stix under the canopy of the plant to attract the adult gnats. Gnat Stixs are made from yellow sticky paper and the gnats are attracted to the bright yellow. Once they land on the paper they cannot get off of it. Replace every other day.
Place slices of potato on the top of the soil under the plant. The larvae will be attracted to the moisture and sugar. Lift off and you should be able to see the larvae on the potato. Discard away from the plants, outdoors. Replace the potato slices each day until you see no more larvae.
Use a pyrethroid-based insecticide on the surface of the growing medium. These come in sprays and in slow-release spikes that you can insert into the soil. Follow manufacturer's directions on how much and how often to use.