Fungus Gnats

Sciaridae (Family), Soil gnats, Dark-winged fungus gnats

Fungus gnats are small, black flies that resemble tiny mosquitoes. You will mostly notice the adults running across the surface of the soil or flying erratically around the base of the plant.

While the adults are mostly a nuisance to humans, the larvae living in the soil are the true threat to the plant. These larvae feed on organic matter, fungi, and—most dangerously—the delicate root hairs of your plants. This damage can lead to root rot and wilting, especially in young seedlings or plants that are kept in consistently moist soil.

Variants

Aerial (Adults)

The aerial variant (adults) lives for about a week and is responsible for laying hundreds of eggs in the top inch of moist soil. They do not eat the plant but are the primary indicator of an infestation.

Substrate (Larvae)

The substrate variant (larvae) is a translucent, white worm with a distinct black head. These larvae stay hidden underground, making them "invisible" until the plant begins to show signs of decline. Because the larvae require moisture to survive, they are rarely found in dry soil, whereas adults will persist in the air searching for the next damp pot.

Rehabilitation Instructions

Aerial (Adults)

  • Sticky Traps: Place yellow sticky cards horizontally at the soil line to catch adults before they can lay more eggs.
  • Sand Barrier: A layer of sand on top of the soil prevents adults from being able to dig in to lay eggs or emerge after pupating.

Substrate (Larvae)

  • Drought Cycle: Let the top 2–3 inches of soil dry out completely. Larvae cannot survive in dry conditions.
  • BTI Drench: Use "Mosquito Bits" (BTI bacteria) in your watering can. This biological treatment specifically targets and kills the larvae in the soil.
  • Peroxide Flush: Drench the soil with 1 part 3% hydrogen peroxide to 4 parts water. This kills larvae and eggs on contact while aerating the roots.

Care Products

View all