In potting soils and mixes of many houseplants.
Damage is caused by the larvae.
They feed on any organic matter as well as attacking bulbs, roots and other fleshy organs. Delicate seedlings of many plant species can be killed with plants yellowing and often wilting rapidly before death. Look for the larvae, particularly in the upper inch of media in the container. Fungus gnats have been shown to transmit diseases economically serious to the greenhouse industry. The adult has about a 10 day lifespan but during that period may lay in excess of 250-300 eggs.