Fungus Gnats

Fungus gnats are tiny black flies, frequently numerous in greenhouses and around certain house plants. Often called manure flies or mushroom flies, the adults do not feed on or damage plants. The larvae primarily feed on fungi and organic matter in the soil. Sometimes the maggots also feed on the roots of flower crops, especially poinsettias, geraniums, lilies, African violets and chrysanthemums. Heavy infestations cause plants to wilt, lose vigor, and drop their leaves. Larvae are pests because of the damage they cause to plants; adults are considered pests because they fly about the house in large numbers.

fungus gnat maggot
Larvae of fungus gnats (maggots) are white with shiny black heads and grow to about 1/4 inch in length.

fungus gnat adultAdults are black or brown, slender, about 1/8 inch in length and have one pair of delicate, clear wings.

fungus gnat adult
The adults are often confused with mosquitoes because of their long, slender dangling legs.

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Identification and Control Information

[Photos, left to right: David Cappaert, Michigan State University,; Whitney Cranshaw, Colorado State University,; David Cappaert, Michigan State University,]