How to Get Rid of Fungus Gnats for Indoor Plants

If you’ve got any indoor plants, its likely you’ve come across the dreaded fungus gnats! They’re a common pest that unfortunately can be a little tricky to get rid of.

In this post I’m talking about how to get rid of fungus gnats for indoor plants – for good! It’s more of a treatment strategy, really. Read on for all the tips.

How to get rid of fungus gnats for indoor plants | Dossier Blog

What Are Fungus Gnats?

Fungus Gnats are tiny fly-like insects that are attracted to damp soil. The gnats will lay their eggs in damp soil, which become larvae that feed off things within the soil.

While fungus gnats are a pest, they don’t necessarily damage the leaves or the plant itself. The larvae can feed off the roots of the plant, which over time can cause damage. However the main reason to get rid of fungus gnats is because of how annoying they can be, flying around your house!

They can enter your home via a new plant that may already be infested. Some people like to quarantine new plants before introducing them into their home, for reasons like this!

Unfortunately a lot of store-bought soil mixes can also carry the gnats. I’ve repotted plants in the past to find out the soil was infested with gnats a little too late.

Fungus Gnats live in soil | Dossier Blog

How to Get Rid of Fungus Gnats

There’s a few things we can learn about these pests to help successfully treat your plants are get rid of them for good!

  • Because fungus gnats have multiple stages to their life cycle (fly and larvae), it’s important to address both of these stages to successfully rid your house of them.
  • Pests reproduce quickly! So it’s necessary to perform multiple treatments to ensure there aren’t a few left flying around which can continue to breed.
  • It’s always best to treat your whole plant collection. Because these pests can fly, they can easily spread from one pot to another.

Step 1: Getting Rid of the Larvae

The best way to rid your plant soil of the larvae of these gnats is with a soil drench. This basically means thoroughly watering your plants (drenching the soil) until the excess drains with a treatment solution.

There’s multiple options when it comes to treatment, from dishwashing soap to insecticides. Two I like to use are a Neem Oil soil drench or a Hydrogen Peroxide soil drench. Whichever you choose to use is up to you and what you prefer or have on-hand.

Neem Oil: It’s best to use a pure Neem Oil and dilute it to the strength you need at home. The packaging should come with specific instructions on the dilution ratio. Water all your plants until the excess drains with the solution, and don’t rinse the soil after.

Check out this post for more ways that you can use Neem Oil on your plants.

Hydrogen Peroxide: Mix a 1:4 ratio of hydrogen peroxide to water and thoroughly water your plants until the excess drains. Don’t rinse the soil after.

Both of the above options should not harm your plants, however be sure to stick to the instructions!

Treating indoor plants for fungus gnats | Dossier Blog

Step 2: Getting Rid of the Flying Gnats & Preventing Egg-Laying

The soil drench should help deter the gnats from laying their eggs however it can still happen. Because gnats are attracted to damp soil, watering them with the solution will still need a secondary strategy.

Only Water When the Top Layer of Soil is Dry: Fungus Gnats can’t lay their eggs in dry soil, so allowing your plants to dry out perhaps a little longer than normal can be a good preventative. The larvae generally live in the top 1.5″ (3cm) of soil. However, not all plants will be happy with this strategy! If your plants needs watering more often, try the next solution.

Add A Layer of River Sand or Diatomaceous Earth to the Top of Soil: Gnats can’t lay their eggs in sand, so adding a layer of sand to the top of your pot plants is a sure way to prevent them! Diatomaceous Earth is another option which works in a similar way and can kill gnats on impact.

Treating soil for fungus gnats | Dossier Blog

Follow Up Treatments

It’s a good idea to perform a second treatment (soil drench) a week later or whenever you water your plants next. Remember to treat all your plants, even if you can’t see any gnats!

Other Treatment Options

You may have heard of Yellow Sticky Traps for fungus gnats. They are a sticky, yellow sheet that you can place nearby your plants. Gnats are attracted to the colour yellow and will get stuck on the sheet on contact.

While you can manage to catch hundreds of gnats this way, I’ve found they aren’t as effective in getting rid of gnats as it doesn’t address both stages of the life cycle. They can be effective as part of the above treatment plan if you want to attack those gnats from every side!

There’s other treatment options such as cinnamon or peppermint oil on the soil, dish soap soaks, etc etc. However I am yet to try them or find a single solution that will get rid of the gnats for good! Remember to make sure you’re using a treatment strategy that addresses both the larvae and adult gnats.

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8 Comments. Leave new

  • Hey there! I just purchased a pure 100% neem oil but does not give instructions for diluting for use of a systemic treatment. Can you share your ratio with me?

  • After doing a soil drench, you can always bottom water instead of from the top, to ensure the top stays dry long enough to disrupt the cycle.

  • Hi, There are a couple of treatments you haven’t mentioned which are also very effective, non-toxic, and pet safe. They are beneficial nematodes and mosquito bits—bacillus thurigensis (spelling likely off) I use the mosquito bits regularly and then do a beneficial nematode treatment as needed. The gnats turn up at certain times of year where I live and I also do the treatment in my outdoor potted plants which helps slow introduction indoors—I add them whenever I use new bagged soil because as you say, commercial potting soilis more often than not are infested with fungus gnats, as are most houseplants I purchase. I find beneficial nematodes and bacillus thurigenses treatments to be easier to use with plants than the neem oil, hydrogen peroxide drench, or peppermint oil, because there is no danger of using too much and damaging the plant and also you don’t have to deal with those smells in your house!

    • Hey Rebecca! That’s true, there’s lots of other methods out there of treating gnats too. This is my preferred method and what I’ve found works best. I’ve heard of so many different remedies but as long as they do the job, that’s what counts! 🙂

  • Hi There😀I’ve read your blogs on FLFquite a few times and loved your info! But I’ve never been quite sure what “ let the top few inches feel dry before watering again” . I wonder dies that mean it can still be moist down below? Because if you dig alittle deeper it’s alittle moist.

    • Yes that’s exactly what it means! We should never let the whole pot dry out or the plant would die. When the top 1-2″ feels dry, it is a sign that the plant is ready for more water. The soil will always feel more moist further down the pot and that is ok 🙂

  • Thank you SO much for these great ideas! I have used cinnamon before, but that is just a “band aid” and doesn’t get rid of the pesky little bugs. I will definitely be using the Neem Oil method, and instead of decorative moss, I’ll use the sand on top for the plants that can take it. Thanks again! 😊🌿

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