Size, Shape and Colour: Fungus gnats are small midge-shaped flies around 2mm long, which are usually black in colour. The young larvae are difficult to see with the naked eye due to their small size and translucent bodies.
Biology: Adult female fungus gnats deposit approximately 100 to 200 tiny eggs on the surface of the soil close to the stem of a plant. The life cycle of the gnat continues as they hatch in 4 to 7 days into the larval stage. The larvae are no more than 1mm long when they first emerge, but can grow to ten times that before pupating. This can take as long as 20 to 25 days at room temperature or as little as 1 to 2 weeks at hotter temperatures for example in a greenhouse.
Preferred Foods: Fungus gnats feed mainly on dead organic matter but the larvae will feed on young seedlings which can kill a young plant. Larvae can also survive on patches of mould on greenhouse floors and benches.
Habitat: Fungus gnats love moist soil, and soil rich in organic matter (peat moss, etc.). The larvae will stay beneath the soil surface where it is moist. They are extremely common pests, which are usually found around most house and greenhouse plants.