Fungus Gnats: Identify Them | Find Them | Get Rid Of Them

by | Flies, Insects

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If you have what looks like mosquitoes walking around your indoor plants or you’re finding worms with black heads in the potting soil, you probably have fungus gnats.

Fungus gnats are small flies that come into houses to lay their eggs in damp potting soil. Worms, called maggots, hatch from the eggs and eat fungi in the soil. But sometimes these worms also eat the plant’s roots. Within a few days the worms turn into adult fungus gnats that lay more eggs.

Below you’ll find out how to identify fungus gnats, if they can harm you or your family, and how to get rid of fungus gnats once and for all.

In this article, we will cover:

  • How to identify fungus gnats
  • How to tell if you have fungus gnats
  • The causes of fungus gnats
  • Fungus gnats are harmless, except …
  • How to get rid of fungus gnats

How to identify fungus gnats

Photo of a fungus gnat with labels to identify a fungus gnat fly
To identify a fungus gnat, look for a small fly that looks like a mosquito with a slender gray-black or brown body, 2 long antennae, and 6 long legs.

The following table gives a list of characteristics on what to look for to identify a fungus gnat:

Known asFungus gnats
ColorGray-black or brown body
Average length1/8 inch (3 mm)
Description – Look a lot like mosquitoes
– Long, slender body
– 6 long legs
– 2 long antennae
– 2 transparent wings
Flight patterns – Unpredictable flight pattern
– Slow fliers
– Not strong fliers; they prefer to walk on soil with short flights or hops along the way
Attracted to / Where to find fungus gnats   – Look for fungus gnats: on soil, especially the soil in pot plants; walking over plants; and wherever there’s decomposing material
– If there’s a bad infestation, fungus gnats can leave slime trails on plants or pots that look like they were made by slugs or snails
– Fungus gnats love moisture and often spend time in bathrooms, laundry rooms, and crawl spaces
EggsEach female can lay up to 300 yellowish-white eggs
Breed – Breed outdoors in summer and indoors all year round
– Eggs are laid on soil, in rotting wood, on animal waste, and in overwatered pot plants
– Maggots are worm-like creatures that hatch from the eggs. Fungus gnat maggots have a white or see-through body and a black head
– The maggots eat fungi and organic material in the soil and nibble on plant roots
– Within 3-4 days, maggots turn into adult fungus gnat flies
EatYoung fungus gnats (larvae / maggots) eat:
– Fungi, including mushrooms
– Plant roots
– Organic fertilizers
– Compost
– Grass clippings
– Leaf mold and plant material

Adult fungus gnats eat:
– Water
– Flower nectar
Most activeDuring the day, especially mid-morning and at sunset

How to tell if you have fungus gnats

Fungus gnats are small flies with slender bodies, and long antennae and legs. They look a lot like mosquitoes, but fungus gnats don’t bite. They live on damp potting soil and tend to hop or walk around rather than fly around.

You can tell you have fungus gnats if:

  • You find dead flies that look like mosquitoes lying near your potted plants
  • There are live flies that look like mosquitoes sitting by your windows, especially if you have pot plants close by
  • You see fungus gnats walking or hopping away from you when you look closely at the soil in your pot plants
  • You have slime trails on pots or plants but there are no snails or slugs around
  • Your indoor plants are wilting
  • You find worm-like maggots that have a white or transparent body and a black head
Photo of a fungus gnat maggot to show the white body and black head
Fungus gnat maggots have a transparent or white body and a black head. Most flies’ maggots have a white head.

The causes of fungus gnats

Fungus gnats are attracted to fungi growing inside a house, especially in potting soil. Fungi is more likely to grow in houses: built in humid areas; with leaking pipes; with little ventilation to release steam from hot baths and cooking; or when there are pot plants that get too much water.

The most common cause of fungus gnats is overwatered pot plants. When you overwater indoor plants, the roots can start rotting from sitting in water for too long and fungus can start growing on the soil. These are the perfect conditions for fungus gnat maggots to thrive.

Want to know how fungus gnats get inside? Click here for a list of all the ways flies get into your house.

Fungus gnats are mostly harmless

Fungus gnats are annoying, but they are also harmless and can’t bite, sting, or make us sick. The only time fungus gnats really become a problem is when there is an infestation and there are many maggots eating the roots of plants or seedlings. Over time, the plants under attack may wilt and die.

How to get rid of fungus gnats

Below is a list of the best methods and products from Amazon that you can use to prevent and get rid of fungus gnats:

Don’t bring in fungus gnats: Inspect pot plants and their soil carefully before buying them and bringing them into your home. Turn over the top of the soil to look for maggots, to make sure the pot isn’t infected with fungus gnats.

Reduce water in soil: Feel the soil in your own indoor pot plants. If it’s very wet, stop watering the plants and let the soil dry out. Or start watering pot plants in their trays, so the plants suck up the water from the bottom and the topsoil stays dry.

You can also put a layer of houseplant mulch or sand on top of potting soil, to prevent and kill any fungus gnats or maggots living in the topsoil.

Catch gnats with sticky traps: A popular and easy solution is placing sticky traps, like these from Amazon, in your pot plants. The flies get stuck to the traps, which can then be thrown out.

Use good worms: Release nematodes in the soil of your pot plants. These microscopic worms eat fungus gnat maggots.

Don’t apply pesticides or add fertilizer after releasing nematodes in the soil as these will kill the nematodes.

Try a natural biotoxin: Have children or pets and don’t want to harm birds or bees? Many people have had great success in getting rid of fungus gnats with these mosquito bits:

  • Simply sprinkle mosquito bits on top of potting soil or mix it in with your potting soil before planting plants. The bits will take care of any fungus gnat larvae in the soil.
  • To make a liquid that will kill gnats in soil, mix 2 tablespoons of bits in half a gallon of water. Leave for 20 minutes, then strain the water and remove the solids. Water your indoor plants with this solution. Use this solution to water you plants for the next few waterings, until you no longer see any fungus gnats or maggots.  

Drench your soil: Kill any fungi in your soil along with adult fungus gnats, eggs and larvae by drenching your soil with this root cleaner.

Use only 1 ounce per gallon of water – any more than that and you risk hurting your plants. Then pour 1 cup of this mixture at the base of each 1-gallon pot plant. 

The good news is that fungus gnats can’t become immune to this solution like they do with other products, and it kills them on contact. It’s also safe to use on soil where you grow fruits, vegetables, and flowering plants.

I'm Monique. I love gardening and spending time in my backyard growing things. Here's where I share what I know about backyard pests and what to do about them, so you can enjoy your yard too.

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Monique loves gardening and spending time in her backyard, where she grows flowers, succulents, herbs, fruits, and vegetables.

Monique spends a lot of time researching how to protect her backyard from harmful pests and trying to attract beneficial insects and animals.

She shares everything that she learns and tests here at Backyard Pests.


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