Fungus Gnat Biology

Fungus gnats are a type of short-lived fly that is found throughout the United States. They are found frequently around indoor potted plants and greenhouses. Adults are also attracted to light so large groups of fungus gnats may be noticed next to windows. In fungus gnat biology, they inhabit a wide range or commercial and ornamental plants, and can cause significant damage during certain life stages. Interestingly, adult fungus gnats are actually considered to be important pollinators for several species.

Adults can reach a length of 1/5 of an inch. They are generally dark in color and have transparent wings. Similar to mosquitoes, they have long, thin legs and a long body. Fungus gnats are considered poor fliers, and are more likely to be seen walking on plants when undisturbed.

In fungus gnat biology, females lay between 100-200 eggs in clusters on organic rich soil. Hatching usually occurs within four to six days. Larvae emerge from the egg shells and begin feeding on the plant roots. After two weeks, the larva spins itself into a cocoon and sheds it skin. In another week, a pupa is formed in which the fungus gnat finishes developing under the soil. The adult emerges within a week. More females are born then males which allows for a faster increase in the fungus gnat population. Fungus gnat life cycles occur within 21-40 days depending on temperature and humidity.

Adults do not carry diseases transmissible to humans and are generally considered more of an annoyance as they only feed on the fungus surrounding the plant. The larvae stage is what is damaging as they eat the roots. This hinders plant growth and allows access for potential diseases to attack. Fungus gnats require high humidity, so over watering may lead to favorable breeding conditions.

Knowing the life cycle of fungus gnat biology, it is possible to get rid of these pests. Good sanitation is important in removing fungus gnats. Eliminating algal growth, cleaning up plant debris, and fixing leaks are old good management strategies. Reducing moisture in the soil by less watering and better airflow is also advantageous. Biological control agents, such as insect-attacking fungus, may have to be introduced.