Flies
Fungus Gnat
Bradysia spp.
Quick ID Markers
1Tiny, 1/16"–1/8" long, dark gray to black
2Long slender legs relative to body size
3Smoky gray wings with distinctive Y-shaped vein
4Slow, weak, erratic flight near soil
5Found hovering near houseplants or potting soil
Habits & Biology
Larvae live in moist potting soil and feed on fungi, decaying organic matter, and plant roots. Adults are harmless but annoying. Overwatered houseplants are the #1 source of indoor fungus gnat infestations. Life cycle 3–4 weeks.
Typical Hiding Areas
In and around houseplant soil, potting mix bags, greenhouse benches, and any moist organic media indoors.
Signs of Activity
Tiny dark flies hovering near houseplants
Adults running on the soil surface when plants are disturbed
Larvae visible in soil (tiny white maggots with black heads)
Wilting or yellowing plants from root feeding in heavy infestations
🗓️ Seasonality
Year-round indoors wherever houseplants are present. Populations explode quickly in overwatered plants.
⚠️ Mistaken Identity
Drain Fly (fuzzy wings, moth-like, found near drains)Fruit Fly (red eyes, found near food)Shore Fly (stouter body, found in very wet growing media)
🧪 Treatment Plan
Fungus gnat control requires letting soil dry out combined with sticky traps and a soil drench. Overwatering is the root cause.
Allow the top 2 inches of potting soil to dry completely between waterings. Larvae cannot survive in dry soil. This alone breaks the breeding cycle.
Most houseplants are overwatered — fungus gnats are often a sign of this
Bottom-watering plants helps keep the top layer of soil dry
Prevention After Treatment
- •Water houseplants only when top 2" of soil is dry
- •Use well-draining potting mix
- •Avoid leaving water in saucers
- •Inspect new plants for gnats before bringing inside