Weapons of Gnat Destruction: A Guide to Killing Fungus Gnats

Adding a 1-inch layer of sand or oyster shells on top of the soil prevents adults from laying eggs and keeps the surface dry.

Reviewers consistently rate Mosquito Bits or Mosquito Dunks as the most effective long-term solution. Creating a "tea" by steeping these in water for 24 hours and then watering your plants kills larvae in the soil using BTI bacteria.

For severe infestations, beneficial nematodes (microscopic worms) can be watered into the soil to hunt and eat gnat larvae. 2. Fruit Flies

A mixture of 1 part 3% hydrogen peroxide to 4 parts water kills larvae on contact when used for watering.

Getting rid of gnats effectively requires a dual approach: to stop them from breeding and treating the breeding grounds (soil or drains) to kill larvae and eggs. Best-Reviewed Solutions by Gnat Type 1. Houseplant (Fungus) Gnats These thrive in moist soil and decaying organic matter.