Fungus gnats guide image
Plant pest guide

Fungus gnats

Signs: Tiny black flies around wet potting mix; larvae live in damp soil.

Signs: Tiny black flies around wet potting mix; larvae live in damp soil.Organic control list: Prevention note: Stop keeping soil constantly wet.

Quick facts

Signs: Tiny black flies around wet potting mix; larvae live in damp soil.

Organic control list:

Prevention note: Stop keeping soil constantly wet.

  • Let the top layer dry.
  • Use yellow sticky traps.
  • Bottom-water when appropriate.
  • Use BTI mosquito bits or beneficial nematodes.

What to do next

  • Isolate the plant if it is indoors or in a crowded collection.
  • Inspect leaf undersides, stems, soil surface, and new growth.
  • Physically remove what you can with water, wiping, pruning, or hand-picking.
  • Use the lowest-risk organic control that matches the pest.
  • Repeat checks because eggs and hidden life stages often survive the first treatment.

Watch-outs

Do not spray first and identify later. The wrong treatment wastes time and may stress the plant.

FAQ

How do I use this plant pest guide?

Start with the light, soil, water, symptom, or purpose notes on this page, then make one careful change at a time.

What is the biggest mistake with Fungus gnats?

Do not spray first and identify later. The wrong treatment wastes time and may stress the plant.

When should I get more help?

Get local help if the plant is valuable, symptoms are spreading quickly, or outdoor disease and pest problems may affect nearby plants.