Management strategies include insecticides and repotting (or rerooting) infested plants. I do not recommend the use of chemical insecticides for fungus gnats in the home. Fungus gnats are considered a nuisance pest and not usually that plentiful in our arid environment. Yellow sticky cards attract fungus gnats and are often used for monitoring. Placement of several yellow sticky cards may also be somewhat effective in reducing their numbers. The yellow color attracts gnats and they get stuck to the card. Electrocutor-light fly traps will attract and kill adult fungus gnats at night.
Bacillus thuringiensis serotype israelensis (Bti) is a biological control that can be used to manage fungus gnats. It is a safer alternative to chemicals and is applied to the soil of infested plants to control larvae. This product is packaged for homeowners and sold as Gnatrol. Other biological controls are available for fungus gnat management. Beneficial nematodes can be purchased that parasitize fungus gnat larvae. These microscopic roundworms are available from specialty garden catalogs. Steinernema feltiae is the nematode species that is most effective against fungus gnats and it is sold under the trade names Nemasys, NemAttack, Enton-em, X-Gnat, and Magnet. Applications of these nematodes have eliminated fungus gnats from the houseplants in our offices. Additional fungus gnat information and photos are included below.
Before you launch a control campaign for any pest, remember the four steps of integrated pest management (IPM). These are: 1) correct identification of pest; 2) monitor for damage (or nuisance) threshold; 3) once the threshold is reached, apply multiple prevention and control measures; and 4) monitor for control effectiveness and revise strategy if needed.
IPM is a standard approach for minimizing damage from any pest species. All gardeners would do well to memorize these steps and use them whenever pest issues arise. The key points are correct pest species identification and accepting some damage before control measures are applied. If you jump the gun and apply pesticides before a damage threshold is reached, you will most certainly kill some beneficial (predators and parasites) and/or benign insects.