They are highly attracted to growing medium that contains peat moss and pine bark. Fungus gnat larvae have a black head capsule, a characteristic that distinguishes them from shore fly larvae. Larvae are generally located within the top 1 to 2 inches of the growing medium surface, but they have also been found in the bottom of containers near drainage holes. They are highly attracted to cuttings before callous formation. Fungus gnat larvae undergo four larval instars before entering a pupae stage.
Adults emerge from the pupae after approximately four to seven days.
A generation from egg to adult can be completed in 20 to 28 days, depending on temperature. The best approach to minimizing fungus gnat problems is to understand the conditions that favor these insects. Several conditions in the greenhouse may lead to fungus gnat problems. Greenhouse managers who understand the conditions that favor fungus gnats can implement the necessary cultural management strategies. First, avoid overfertilizing plants.