Prevent and Get Rid of Fungus Gnats

We love having houseplants in our home. They breathe life into a house and add a nice colorful flair.  Houseplants bring a wonderful, lovely dose of nature indoors where you need it most, further helping us by purifying the air in our homes.

At some point, you might notice some unwelcome visitors making your houseplants their home. Fungus gnats, also known as soil gnats, are small dark insects that look like fruit flies and live in the soil of houseplants. You might notice them when you water your plants or disturb the soil in other ways.

What Are Fungus Gnats

Indoor plants have only a few natural predators that want to kill fungus gnats.  So unfortunately, the only way to get rid of fungus gnats in your house is to kill off the pests you have and treat your plants to prevent future infestations.

The adult flies lay eggs in the soil.  The eggs hatch into larvae that eat plant roots and fungi in the soil. Then they suddenly appear again in houseplants after the larvae hatch into adults.  There is about a 35-day lifecycle from egg hatch to adults laying new eggs.

While these pests are a nuisance in noticeable numbers, it might be comforting to know that the adults are harmless insects that do not bite.  They don’t do much damage to strong, healthy plants, but they can cause yellowing, stunted growth, and even death in seedlings and more fragile plants.

Nuisance problems with fungus gnat adults tend to be most noticeable during late fall and winter, for a couple of reasons:

  1. Houseplants that live outdoors during warm months will commonly start breeding fungus gnats. When these plants are brought indoors, populations may increase due to the warmer temperatures found in homes.
  2. Fungus gnats may hitchhike on a new plant brought in from the nursery.
  3. People are indoors more during the colder months, making it easier to notice an infestation.
How to Get Rid of Fungus Gnats

Killing off soil gnats is not very difficult.  Here’s how to naturally treat your houseplants and get rid of gnats in the soil.  Make the natural habitat inhospitable.

This means drying out the soil they live in because fungus gnat larvae need moist soil. If you let it dry out completely before your next watering, it will get rid of the gnats in the soil and discourage new adults from laying their eggs.

Yellow Houseplant Sticky Stakes

Use yellow Houseplant Sticky stakes stuck in the soil of the pot to trap the adults.  The yellow color will attract them to the sticky card where they will become trapped.  Also good to use these cards as indicator cards to help identify if you are having a problem or how sever the problem is.

Treat the Soil Surface
  1. Add a few drops of liquid dish soap to a cup of water. Spray the top of the soil with this to kill the larvae. Repeat this process a week later to kill newly hatched eggs.
  2. Sprinkle a layer of diatomaceous earth over the surface of the soil creating an inhospitable environment for the adults to lay their eggs.
  3. Pull out the big guns – sprinkle a layer of Bonide insecticide granules over the soil surface to kill the larvae.
How to Prevent Fungus Gnats

Neither fungus gnats nor their larvae can survive in dry soil, so let your soil dry out completely between watering as often as possible.

This will help the topsoil (where the gnats lay their eggs) stay dry while keeping your plants hydrated and happy.

Replace the top inch of soil with sand or gravel to create a dry environment and nutrient-rich fungus to munch on. Without their needed source of food available, they won’t want to lay their eggs.