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Goodbye, Fungus Gnats! How to Get Rid of Gnats in Plants

Now you can enjoy your houseplants without having to tolerate any unwanted guests. Wondering how to get rid of fungus gnats? You aren’t alone! Learn how to prevent and how to get rid of gnats in plants naturally. 

Prevent and get rid of fungus gnats

There’s something refreshing about having houseplants inside your home. They breathe life into a house and also 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. 

However, at some point, you might notice some unwelcome visitors making your houseplants their home. I’m talking about fungus gnats—those annoying little flies that appear whenever you water your plants. Ugh! Do these houseplant pests plague your plant babies too? 

Don’t worry, if you are having gnat problems, there are simple—and natural—ways to not only prevent but also get rid of fungus gnats in soil.

Disclaimer: First, a disclaimer. I love living things and try to support natural insects anytime I can. For example, in the outdoor garden, I work to create a natural ecosystem that supports predators for the pests that attack my plants. 

Indoor plants, however, have only a few natural predators that want to kill fungus gnats – the people and pets they annoy! Unfortunately, the only reasonable 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.

In this post, we will cover:

What Are Fungus Gnats and How Do They Get in the House?

plants being replanted to prevent pesky fungus gnats

Fungus gnats, also known as soil gnats, are small dark insects that look similar to fruit flies and live in the soil of houseplants. When you have them, you will notice them when you water your plants or disturb the soil in other ways. 

One way to get fungus gnats is to leave your houseplants outside. Most often, though, they come straight from the nursery. You don’t realize it because they hide in the soil until you bring them home unknowingly. 

Their larvae eat plant roots and fungi in the soil. Then they suddenly appear in houseplants after the larvae hatch.

Why Are Fungus Gnats Bad?

plant being replanted to avoid fungus gnats

While these pests are a nuisance in noticeable numbers, it might be comforting (on some level) to know that the adults are harmless insects that do not bite.

Also, they don’t do much damage to strong, healthy plants, but they can cause wilting yellowing leaves, stunted growth, and even death in seedlings and more fragile plants. 

But honestly, nobody wants a swarm of gnats flying in your face every time you water your houseplants. Yuck.

When Are You Most Likely to Find Fungus Gnats?

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. 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 really not very difficult, and thankfully, you don’t need to bug bomb your home (yay). It all has to do with disrupting their life cycle and making your home inhospitable for these pests. Here’s how to naturally treat your houseplants and get rid of gnats in the soil.

Make the Natural Habitat Inhospitable

Fungus gnat larvae need moist soil to survive. By letting it dry out completely before your next watering, it will get rid of the gnats in the soil and discourage new adults from laying fungus gnat eggs, thus effectively cutting out the larval stage altogether. 

Use a Soap-and-Water Mixture

Take a cup of water and add a few drops of liquid dish soap or liquid Castille soap. Use a spray bottle to spray the top of the soil with this to kill the larvae. Repeat this process again in a few days to ensure that you have killed all of the larvae.

While some people recommend vinegar traps, I have found the soap and water to be more effective. Vinegar (and in particular a bowl of apple cider vinegar) is better suited for making a fruit fly trap.

Use Sand or Gravel

Fungus gnats only lay their eggs in the top inch of soil. Replacing that top inch with sand or gravel creates a dry environment and robs them of nutrient-rich fungus to munch on. Without their needed source of food available, they won’t want to lay their eggs. 

You can also use pretty decorative aquamarine rocks and add a splash of color to some of your favorite plant babies.

cactus in a cage on a tray of pink gravel to help prevent fungus gnats

Dispose of the Top Layer of Soil Outdoors

The eggs can still hatch. Let them hatch outside rather than somewhere in your home. You don’t want to just move your pests from one part of the house to another.

By taking all of these steps, you can naturally control and prevent fungus gnat infestations.

How to Prevent Fungus Gnats

plant in a white container in front of a blue painting.

Let’s chat about the steps you can take to prevent these annoying pests from ever entering your life in the first place!

Don’t Overwater Your Houseplants

Make sure you aren’t overwatering your plants. Moisture is a big plus for gnats, so to make their new environment inhospitable, you need to let the soil they live in dry out completely. 

Neither adult gnats nor their larvae can survive in dry soil, so let your soil dry out completely between watering as often as possible. Here’s an entire guide devoted to teaching how to water your houseplant properly.

Water From the Bottom

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

Store Extra Potting Soil in an Airtight Container

If you keep your potting soil in the bag it comes in, fungus gnats can easily get in and lay their eggs. However, the eggs need air to survive, so airtight containers like buckets with tight-fitting lids will keep gnat larvae at bay.

Now That Takes Care of Gnats, but What About Other Houseplant Pests?

Fungus gnat free cacti in a windowsill

Expert David Squire popped by as a guest of Garden Therapy to share information on 8 of the other most common indoor plant pests and how to get rid of them. He has some great tips and tricks here for getting rid of houseplant pests!

Love houseplants? These Posts Are Great Reads

Comments

  1. I have tried everything! I have NEVER had this problem before but last summer I bought potting soil and it came with GNATS!! I have tried sand and I have tried the soap and water.. The gnats drive me crazy!! Just when I sit down after a hard day of work and start to relax…one appears and flies around me and taunts me!!

    WHAT AM I DOING WRONG?????

    ////

    Reply
    • I had a HUGE fungus gnats infestation and hydrogen peroxide was a god’s send! Peroxide will kill any gnat larvae on impact so add some to your water before your next watering. I also used mosquito dunks that you can either grind up and sprinkle over your plants or soak the whole thing in water and only water your plants with that water. The main ingredient in mosquito dunks are BTI which contains spores that produce toxins that specifically target and only affect the larvae of the mosquito, blackfly and fungus gnat. The gnat larvae feeds on it, instead of the roots, and it kills it from the inside before it gets a chance to grow. It’s active both in dry and wet form and nontoxic to humans/pets/plants. Diatomaceous Earth, as a topper, also works well to kill ALL bugs, including fungus gnats. While you wait for the larvae to die off (each fungus gnat can lay up to 300 eggs (!!!!)) hang some sticky tape, the wavy kind, to take care of the flying fungus gnats. A plug in mosquito catcher would also help… if you combine a few of these things, you can get rid of them QUICKLY. Hope this helps!

      Reply
  2. This is the First time i have fungus gnats, my house was always full of plants and never had issues. I tried so many natural metods and my plants are almost dying from not being watered but that didn t seem to help. I will try to find some spray to buy because they are so manny that can t take it anymore with all the traps and still sooo many.

    Reply
  3. I have so many succulents and cacti, and I had planted then about a month ago. Now, every time I sit down in my room, and observe my plants there are like a bigilion gnats. I left them outside so the gnats will fly away but instead more gnats come in. I had a rotten cactus and then had magets all over it. Yuck. So I removed the rotten plant and now there are more gnats. I am so fed up.

    Reply
  4. I just had to write and say THANK YOU. I had taken any and all steps to get rid of these gnats, but only treated the plants themselves and still they were buzzing around. Then I saw that you mentioned they can live in the bag of soil. I have an unopened bag that I bought a few weeks ago and placed in an uncovered container. The bag was unopened, but they still got in! There were hundreds of them inside the container, so I’m throwing it all out and hopefully that’ll do the trick. Thanks so much!!

    Reply

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