Fungus Gnat (Bradysia spp)

The larvae of fungus gnats live in moist soil and feed on decaying organic matter. These conditions are abundant outside in autumn and nearly year round in potted plants. They are usually seen flying at windows and around house plants. Homeowners may notice these small flies when watering potted plants.

Identification:
3-4mm in length Greyish to black in colour with a distinctive pointed abdomen. They are slender, mosquito-like, and delicate with long legs and one pair of clear wings.

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. Complete life cycle occurs within 21-40 days depending on temperature and humidity.

Control:
Control of fungus gnats in the house is relatively simple. Adult fungus gnats are attracted to moist, organically rich soil. Examine all house plants for "over-watered soil." Allowing the soil to dry out for several days (or longer) is probably the best control of these pests. The larvae live in the top layer of soil. If the top layer of soil becomes dry, the larvae will die and the adults will not have a place to lay their eggs. Flying adults can be controlled using a knockdown aerosol or ULV in extreme infestations. DO NOT apply public health insecticides direct to plants. There are a number of pyrethroid-based insecticides that are available for use on houseplants available from garden centres.

Products to control Fungus Gnat: