WSU Extension


Caption: Dark winged fungus gnat
Photo by: Ken Gray
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Fungus gnats

(revision date: 7/14/2015)

Use Integrated Pest Management (IPM) for successful pest management.

Fungus gnats are small (1/8 inch) gray-black flies often noticed around houseplants and windows. Most species inhabit fungi or dead plant material, but a few species have maggots that injure plant roots. Even non-pest species can injure plants if their preferred food source of decaying plant material is not available. Fungus gnats are very dependent on high moisture levels in the soil and are particularly troublesome when overwatering occurs.
Management Options

Non-Chemical Management
  • Do not overwater houseplants. Overwatering provides ideal breeding conditions.
  • Use houseplant soil moisture meters to more accurately monitor soil moisture levels. Let soil “dry down” within reasonable limits between watering.
  • Hang sticky yellow traps over houseplants as a first step in suppressing heavy adult populations.
Select non-chemical management options as your first choice!

Chemical Management

Be sure to remove breeding sites. Pesticide applications are not recommended.

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Caption: Dark winged fungus gnat
Photo by: Ken Gray