How do I get rid of fungus gnats?

Adults are annoying but harmless. The larvae live in damp topsoil and can chew fine roots, which hurts seedlings and cuttings most. Water less often, and water more per session instead, so the surface dries. A layer of dry material on top also helps.

Yellow sticky traps catch the adults and show you how bad it is. For the larvae, biological control (beneficial nematodes or Bti) works well in soil. Blue traps are better if thrips are also around.