Fungus gnats include several species of small, dark flies that plague lawns, shrubs, and houseplants. Often mistaken for tiny mosquitoes or black flies, adult fungus gnats typically grow up to 1/8 inch long. Their dark, gray-black bodies have transparent grayish wings, long legs and long antennae.

Fungus gnats damage plants when these pests are in their larval stage. These translucent wormlike pests have black heads and grow up to 1/4 inch long. The larvae generally stay within 2 to 3 inches of the soil surface. Where heavy infestations exist, you may see fungus gnat larvae on the soil surface after heavy rain or watering.


Pesky mini-swarms of adult gnats are usually the first sign of an infestation. As fungus gnat larvae feed on plant roots, infested plants wilt and display weak, unattractive growth. As root damage increases, root rot disease may set in. Rotting roots attract larvae and encourage more feeding. Affected plants deteriorate quickly.

Outdoors, you'll find adult fungus gnats hovering near decomposing plant debris, including piles of grass clippings or leaves and mulch around foundations. Indoors, fungus gnats stay close to the houseplants they infest. However, they may migrate toward bright windows, lighting, and your favorite refreshments. Yellow insect sticky traps also attract these flying pests.


Effective fungus gnat control targets plant-damaging larvae and nuisance adult gnats. For outdoor container gardens and landscapes, spray thoroughly to treat soil and vegetation where adults hide. Always take indoor plants outdoors for fungus gnat treatment; allow the product to dry completely before bringing plants back inside. Amdro brand offers several options to kill fungus gnats outdoors and reclaim your yard:

  • Amdro Quick Kill Outdoor Insect Killer Ready to Spray kills fungus gnats by contact, then it keeps working for up to three months. Just attach the container to a regular garden hose and spray your lawn or plant surfaces to the point of runoff. No measuring or mixing on your part — the container does it automatically.
  • Amdro Quick Kill Outdoor Insect Killer Concentrate, with a convenient measuring cap, kills fungus gnats by contact and keeps protecting your lawn and landscape for up to three months. Dilute the product according to label instructions in a regular pump-style garden sprayer. Then spray plant and soil surfaces thoroughly.


For maximum results, force gnats from their hiding places before you treat. Gently shake gnat-infested plants and water the soil, then treat your target area thoroughly.

Always read product labels and follow the instructions carefully.

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