How Do I Get Rid of Flies (Fungus Gnats) In My Houseplant?

by | Last updated Mar 25, 2022

What-Are-Fungus-Gnats

Fungus gnats can infest and destroy your house plants, and watching your plants suffer is one of the most frustrating experiences. You will notice these little winged creatures flying around your plants or crawling out of the soil while watering.

While they are harmless to humans as they don’t sting, bite, or transmit diseases, they can wreak havoc to your plants. But luckily, you can get rid of them and take preventative measures to keep these insects from reinfesting your plants.

What Are Fungus Gnats?

What Are Fungus Gnats
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They are small flies, about a quarter of an inch in size, but they aren’t too small to cause damage. They belong to the Sciaridae family of insects that also includes Diptera, Ditomyiidae, Keroplatidae, Diadocidiidae, and Bolitophilidae.

These flies are naturally found in moist forest areas and eat decaying plants like mushrooms, but they can thrive in any damp environment. Unlike other insects, they don’t hibernate in winter, which means that they can be an all-year-round problem. Their larvae feed on algae and decaying plants and they seek out moist places such as:

  • Mildew and mold
  • Moist and brightly lit places such as windows
  • Warm and wet environments
  • Overwatered houseplants

How to Get Rid of Small Flies in House Plants?

If your houseplants are infested with fungus larvae, you can use the following ways to get rid of them in order to rectify the situation.

Use Soil Covers

Use decorative moss soil covers, gravel, or sand to replace the top inch of soil. Not only will it deter fungus gnats but it’ll also keep them from laying eggs in the soil.

The top layer will add more beauty and character to your houseplant as well. You can also use a specially designed non-toxic gnat barrier for the same purpose.

gnat barrier for houseplants
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Use Water and Hydrogen Peroxide Solution

Using three percent hydrogen peroxide is an effective way to get rid of fungus gnats. All you need to do is to mix four parts of water and one part of hydrogen peroxide and water your plants with this solution. Bear in mind that this solution must only be used when your potting medium’s top is dry. Otherwise, you’ll run the risk of overwatering your plants.

You’ll start hearing effervescent sounds while pouring this solution into the soil, which is normal. On contact, the hydrogen peroxide and water solution will kill gnat larvae, which will then convert into water and oxygen molecules. The method is completely safe and it can also help your plant with root rotting. This method must not be used more than once a week.

Dry Potting Soil Out

As discussed above, fungus gnats thrive in moist environments. While it’s tempting to water your plants regularly, it’s essential to ensure that the soil container isn’t always damp or wet. Not only will it minimize the risk of overwatering your plants, but it also won’t attract other harmful insects.

Moist soil is an ideal place for algae and mold to grow and these are the things that fungus gnats love. Keeping the top one or two inches of your soil dry will allow you to create an environment that is not flies-friendly.

If the surface layer of soil is damp, don’t water it. It’ll also keep the already present gnat eggs from hatching in the first place. Watering your houseplants with the right frequency is also important to keep them healthy. Keeping the surface of your soil dry is a simple yet effective way to get rid of them.

Water Houseplants from the Bottom

bottom watering house plants
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Watering your houseplants from the bottom is another trick to keep fungus gnats at bay. 

Typically, fungus larvae live and thrive in the top layer of your soil. This top layer is usually moist because of the way you water your plants.

Watering from the bottom will help you keep the top layer of soil dry and ensure plants’ health. You can use a cachepot or drip tray to water plants from the bottom. This way, the plant will soak up the water it needs through the container’s drain holes.

It’s important to note that you must not let your houseplants sit in the water tray for a long period of time. 30 minutes are more than enough, and make sure you dump out the remaining water after that.

Repot Your Plants

If you notice that fungus gnat larvae have already infested your soil, you can simply repot the plants. Make sure that you use soil that has a good nutritive value. Get rid of the old infected soil from the container after removing the plant and don’t forget to clean both plant and container properly.

Add fresh soil and repot your plant. Another important factor to keep in mind while repotting your plants is to look for decaying plant matter. If you notice any, get rid of it so that it doesn’t attract fungus gnats again.

Use Yellow Sticky Cards

You might be wondering what yellow sticky cards have to do with plants and fungus gnats. Surprisingly, it’s one of the most effective ways to catch those buggers. It comes in handy if your plants are being attacked in abundance.

yellow sticky cards
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Most fly trap cards are yellow because adult fungus gnats and some other species of insects are naturally attracted to this color. These sticky yellow cards are known as Gnat Stix and you can easily find them from your local plant stores and nurseries.

Once you have these cards, all you need to do is to place them beneath the pot’s canopy. The flies will get trapped in the cards’ sticky surface and it’ll also keep them from laying eggs to minimize larvae population.

Keep Your Unused Soil Safe

You must use sealed containers to store your unused potting soil. That’s because open soil bags can also attract these flies. You can use airtight buckets for this purpose. Not only will it help you keep them at bay, but it’ll also protect your unused soil.

Use Insecticides

If you want to get rid of fungus gnats and their larvae within the shortest possible time, there is no better way than using insecticides. You’ll need to use multiple types of insecticides for larvae and adult gnats because both of them respond differently to different treatments.

Applying insecticides to the surface of the soil is the most effective way to deal with new adults because they are born on the soil’s surface. Since they are born on the soil, they target the algae and the roots of the plant. So, you won’t need to spray the insecticide on the plant.

We recommend you use natural insecticides such as dish soap or neem oil. However, these chemicals won’t be as effective as more powerful commercial products. If you need to see results in a short period of time, use commercial products that come with cyhalothrin, cyfluthrin, bifenthrin, or permethrin.

Using Biological Control Agent

Using Biological Control Agent
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If you want to control fungus gnats biologically, consider opting for a parasitic insect nematode. It’s basically a roundworm type that you can’t see with a naked eye and it can kill fungus gnats easily. However, the method it uses to kill the insects is pretty disturbing.

When you use these roundworms on your soil, they enter their bodies and release bacteria. These bacteria then start consuming the inside of these gnats. While using this method is somewhat diabolical, it’s very effective and helps you get rid of the entire colony of flies within a few days.

Never Reuse the Used Soil Again

It’s tempting to reuse the used soil again to save a few bucks, but it’s not a good practice to follow. It’s equal to asking for trouble. The used soil can have eggs of fungus gnats that can hatch and turn into larvae to destroy your plants. That’s why it’s essential to use sterile and fresh potting soil if you want to repot any of your plants.

How to Identify Fungus Gnats

They appear very similar to small black flies and mosquitos, which means identifying them can be difficult if you’re not an expert. Inspecting the soil is the first step to determine whether your plants are being attacked by them or not. You can use the following tips to identify fungus gnat infestation.

  • The most effective way to identify them is to look for their larvae. If you see any little white specks on the soil surrounding your plant, chances are they’re fungus gnat larvae that have hatched.
  • They can damage your plants a great deal. If your plant is withering or wilting, consider it a red flag and use any of the methods discussed above to get rid of them. A plant withers or wilts when its root gets damaged and the reason behind that can very possibly be these fungus flies.
  • If you see that your plant leaves are falling off or they’ve turned yellow unexpectedly, it can be due to fungus gnats. Keep in mind that the plant shed their leaves normally when they’re getting ready for new foliage. However, it’s not normal for a plant to lose both old and young leaves excessively.

The feeding system of the plant gets damaged because the gnats eat the plant’s roots. This way, the plant fails to get the essential nutrients it needs to flourish and starts losing its leaves. If you notice these signs, inspect the soil for fungus gnat larvae and check the plant roots for damage.

If there are still some healthy roots left, you’ll be able to save your plants by using one or more methods discussed above to get rid of fungus gnat infestation.

Prevention Tips

Getting rid of them doesn’t necessarily mean that they will never appear again. You’ll need to take some preventative measures to ensure that they don’t attack your houseplants again in the future.

Avoid Overwatering Your Plants

Avoid Overwatering Your Plants
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You would already know how critical good drainage is for plants. It becomes even more essential if you want to keep fungus gnats at bay. These insects love plant containers that are always damp and they’ll make their way to lay eggs in such environments.

That’s why you must avoid overwatering your houseplants. It would help if you also used pots with big enough drainage holes so that the soil doesn’t always remain damp. If your soil doesn’t drain well, consider adding some perlite to accelerate the drying out and absorption process.

You’ll also need to plan your watering schedule depending upon the unique needs of each plant. We recommend you avoid watering a plant until its soil has become suitably dry. When it comes to fungus gnats, it’s essential to make sure that the top layer of your soil remains dry.

If any of your plants need more water, consider watering it from the bottom so that the plants get essential nutrients but the top layer of soil remains dry at the same time.

Minimize Plant Debris

For fungus gnats, plant debris is just like a dream come true. The females like to lay their eggs in a damp environment that also has enough resources that their hatched larvae can eat. Clear any debris that is lying around or in the pot after falling from your houseplants. It includes sticks, fruit, flowers, leaves, and seeds.

You should also avoid soil that has bark because it can have decaying organic matter and it can also trap moisture easily. It’ll only attract more flies to destroy your houseplants.

Bottom Line

It’s a little tricky to get rid of fungus gnats but it doesn’t have to be difficult if you use the right methods. First, you need to identify the gnat infestation and then use any of the methods that suit you the best to get rid of it.

Your watering schedule plays a major role in attracting them and also keeping them at bay. Use watering techniques and schedule to create an environment most suitable for your plant!

Shelbi Clifford

Shelbi Clifford

Hi, I'm Shelbi! I am the founder of Houseplant Advisor - a blog for all things houseplants. Whether you are looking to add some green to your home or want to learn about how plants can help improve air quality in your space, Houseplant Advisor is here with the answers. Do you have any questions? Feel free to reach out and ask me anything!

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