Get rid of fungus gnats in houseplants

How to Get Rid of Fungus Gnats in Houseplants? Try Some of These 6 Cool Methods to Catch Gnats!

Have you noticed any miniature black flies buzzing around your beloved plants? Well, aren’t they annoying? These little pests are called fungus gnats, and they can sometimes be quite tricky to eliminate, but it’s not impossible.

All it takes is the right “tools” and patience, and the nasty little enemies will be gone, hopefully for good.  In this guide, I shall tell you more about how to get rid of fungus gnats in houseplants.

There are six simple yet successful methods to eliminate these annoying houseplant pests: by using hydrogen peroxide solution and water, allowing the potting soil to dry, repotting the plant, using sticky traps, applying insecticide, or with the help of biological control agent, that is-beneficial nematodes. 

Here’s the list of topics I shall address: 

  1. What is a fungus gnat and how does it end up on a plant?
  2. Is it difficult to identify fungus gnats on indoor plants? 
  3. Try one of these 6 methods to get rid of fungus gnats
  4. How to stop gnats from affecting other potted plants?
  5. How to create gnats-unfriendly environment?

Let’s get started with solving the fungus gnat problem! 

What Is a Fungus Gnat And How Does It End up on a Plant?

What is a fungus gnat?

Fungus Gnats belong to a family of insects that include Bolitophilidae, Diadocidiidae, Keroplatidae, Ditomyiidae, and Diptera.

These insects belong to moisture-loving houseplant pests and are usually found in damp forest areas. They usually feed on mushrooms, but decaying organic matter is an equally great meal for annoying gnats. 

Unlike some other insects, gnats do not hibernate during winter. What this indicates is that there’s no specific season when they represent an issue- fungus gnat infestations are a year-round problem. 

Тhese miniature enemies are really tiny in size. They grow to approximately a quarter of an inch in length. Don’t let their size trick you into thinking that they are not harmful and unable to make serious damage to a plant. Fungus gnat larvae can be detrimental to plants if not eliminated. 

Despite being relatively tiny, fungus gnats can be very dangerous to houseplants

Talking about the damp environment, here’s the list of conditions that may lead to severe infestations on your plants: 

  • Systematic overwatering (damp soil)
  • Bright light 
  • Mold and mildew
  • Wet or warm surroundings with high humidity levels

From a gnat’s point of view, these conditions are ideal. In case some of these describe your home, you might want to work on making your place less gnat-friendly. 

Is it Difficult to Identify Fungus Gnats on Potted Plants? 

How to identify fungus gnats on plants?

How to be sure that your plant is attacked by fungus gnats? It’s somewhat easier when you spot them, but yet again, they can often be confused with tiny mosquitoes or fruit flies.

One of the simplest methods to do so and clear away all the doubts is to check the plant’s soil thoroughly. If tiny black insects are buzzing around it, you can suspect fungus gnats infestation.

By looking for some tell-tale signs, you’ll be able to identify the enemy precisely and eliminate fungus gnats.

Simple organic test:

  • Believe it or not, a slice of raw potato can help you in identifying fungus gnats presence in soil.
  • Cut a potato into slices or wedges and place them on the top of the soil.
  • If there are fungus gnat larvae inside the soil, they will start feeding on the underside of the slices/ wedges.
  • Once you turn that piece of potato over, you’ll be able to identify how many of them are inside the soil. Interestingly, these slices/ wedges can also help you draw the gnats out of the soil. 

Here’s what you need to do in order to confirm their presence 100%:

Inspect a plant for fungus gnat larvae

Fungus gnats larvae and eggs

If you notice some tiny white specks on the soil of your plant, you can be positive that it’s the fungus gnats you are dealing with. These miniature specks come after the larval stage and they represent the newly-hatched babies. 

Related: Tiny White Bugs in Houseplant Soil

Pay attention to the plant’s overall condition

As with any other issues, damage caused by fungus gnats will change your plant’s appearance. A withering or wilting plant indicates that the root system is damaged. Those are fungus gnats feeding on the plant’s roots.

When they do so, they damage the feeding system, and your plant cannot receive the necessary nutrients. Also, it loses the ability to absorb water well, which overall leads to drastic changes not only in appearance but health as well. 

Yellowing leaves is one more signal that something’s wrong with your plant. Plus, if your plant is losing more leaves than it normally should, or even worse- losing new leaves, chances are it’s attacked by fungus gnats.

Severe fungus gnats infestation

Are your seedlings growing at an optimal rate? 

Fungus gnats are equally interested in infesting both mature and young plants. So, if you have seedlings, but they seem to be growing slower than they should, it could be due to fungus gnats presence. They can interfere with the normal growth rate and significantly slow down your plant’s progress. 

Which plants are more prone to fungus gnats? 

Geraniums, African Violets, carnations, and poinsettias belong to plants that can be severely damaged by fungus gnats if the infestation is not spotted on time. 

Poinsettia is prone to fungus gnats

Try One of These 6 Methods to Get Rid of Fungus Gnats

As I said in the beginning, there are many ways to eliminate the boring invaders, so don’t give up on your plant. Here’s what you can try: 

Mix hydrogen peroxide and water 

Mix a solution of one part of 3% hydrogen peroxide with four parts of water, and you’ll get an excellent potion that is great in killing fungus gnats larvae. This solution is implemented when the top of the soil is dry, to get the most of it. 

Mix water and hydrogen peroxide to eliminate fungus gnats

You should only water your potted plant with this solution when the top of the soil is dry. When you pour the hydrogen peroxide into the soil, you will most likely hear an effervescent sound. 

Once the fungus gnat larvae are killed, the soil will absorb the solution. The great thing is that it is completely harmless to your plant. In case the infestation is severe, or you are applying it for the first time, repeat it to make sure the enemies are gone. 

Let the soil dry out and fungus gnats will be gone

As I already mentioned, fungus gnats thrive in a moist environment. When the soil is excessively wet they will be attracted, as damp soil is ideal for the development of mold and algae.

That’s precisely what gnats love the most. Female fungus gnats adore wet soil, so allowing it to dry will prevent fungus gnat eggs from hatching. 

Female fungus gnats thrive in wet soil

For that reason, you should make a wise watering schedule. Too much water is not beneficial for the plant, and it will only attract nasty insects. Allow the top two inches to dry completely before you re-water the plant. 

Finally, don’t forget to test your soil to check if it really needs water. Insert the finger into the potting medium and evaluate whether the time to rewater it has come. As your experience grows, your evaluation skills will become sharper. 

Repotting the plant to eliminate the unwanted pests

When there are too many gnats or larvae to deal with, the smartest thing to do is repot a plant. Remove the plant from the pot, throw away the infested potting medium and use a new one to repot the plant. 

Of course, don’t forget to disinfect the container before you return a plant. This way, you’ll make sure no larvae have survived, otherwise, your job is pointless. Plus, use gloves when you repot a plant and wash them as well before touching the new potting medium. 

Repot a plant to eliminate unwanted pests

Pay attention to the decaying organic material. As I mentioned, fungus gnats love it and will infest your plant again, if they discover this delicious treat.

Once the plant is repotted, be sure not to overwater it, or else you’ll be dealing with persistent gnats over and over again. 

Related: Can You Reuse Potting Soil?

Yellow sticky cards are an excellent weapon to bid farewell to fungus gnats

They may be unsightly, but they help a lot. These yellow sticky traps work for fungus gnats as well. Just place them under the pot beneath the plant’s canopy and watch the annoying little nuisances get trapped. This will significantly reduce the birth of the next generation. 

Now, you probably wonder why I stressed out the color yellow. Adult fungus gnats are extremely attracted to color yellow. This explains why traps are most often sold in yellow. Look for yellow sticky traps in local nurseries or online.

Yellow sticky traps can capture fungus gnats

Insecticides can help tackle fungus gnats issue 

When nasty pests attack a houseplant, gardeners want to solve the issues as quickly as possible. That’s when they usually reach out for insecticides. 

Keep in mind that different products are required for adult flies and larvae. Having in mind that the pests attack the potting medium, there’s no need to use the product directly on the plant. Apply it to the soil’s surface. 

Regarding the natural and mild options, you can try luck with Neem oil or dish soap, but if you want something truly effective, then commercial insecticides are the only way to go.

Insecticides can help solve fungus gnat problem

Products that contain permethrin, bifenthrin, cyfluthrin, and lambda-cyhalothrin, as well as pyrethrin sprays, will help you get rid of gnats over the long term. Always follow the instructions otherwise you may damage your entire plant. 

Biological control to get rid of fungus gnats in houseplants

Have you heard of insect-parasitic nematodes? These roundworms, invisible to the naked eye are highly effective in eliminating fungus gnats. Steinernema feltiae is their enemy number one. 

Steinernema feltiae is a nematode which destroys fungus gnats

Pour them in a solution and then into the soil to get rid of larvae. The way beneficial nematodes destroy the larvae is quite picturesque, some even say slightly disturbing.

What they do is enter through the gnats’ mouths, breathing pores and start digesting them from the inside. Within approximately four days, the larvae will be gone. 

How to Stop Gnats from Affecting Other House Plants?

Lucky for them, but not you and your plant, gnats spread quickly, and sooner than you notice, they invade other houseplants. 

If you have a plant that is in process of curing, the smartest thing to do is put it into quarantine. This way other plants will remain intact, so you won’t have to deal with multiple infestations. 

Don't keep infested plant near healthy ones- quarantine it!

Fungus gnats spread disease from plant to plant. This means that if one of the potted plants is infested, the other house plants will most likely be as well.

If you want to prevent fungus gnats from spreading on other plants, you can treat them with the same products you applied to the infected plants. By doing so, you will destroy all the potential larvae and eggs before they develop into real insects. 

How to Create Gnats-Unfriendly Environment?

Aside from eliminating the adult flies and larvae, there’s something you can do to prevent them from appearing at all. Soil is the critical spot, so you need to learn how to make it as less attractive to fungus gnats as possible. 

Get rid of plant debris

As I already mentioned, female fungus gnats tend to lay eggs in decaying plant residue. 

Plant debris is some sort of utopia for fungus gnats. It is the main source of decaying plant material and this is where adult female fungus gnats love laying eggs. By maintaining the soil clean from debris, you minimize the chances for potting soil to become populated by fungus gnats. 

Keep soil clean from plant debris

What counts as plant debris? Leaves, flowers, fruit, sticks, and similar are the materials that represent the cozy organic matter. In addition to this, compost filled with bark can be attractive to gnats, as it traps too much moisture, and becomes a potential “home, sweet home” to tiny invaders, 

Do not overwater your plant 

To keep these flying pests at bay, always place your plants in pots that have good drainage and avoid overwatering them. If constantly overwatered, the soil becomes damp, root ball weakened, and appealing to tiny flies. 

The first thing to pay attention to are the drainage holes themselves- make sure there’s at least one, but preferably a couple of them. By adding perlite or peat moss to the fresh soil, you will increase the absorption properties. 

Do not overwater plants and you will avoid fungus gnats

Also, when you water a plant, empty the saucers below after 30 minutes, so that the soil drenches well. The still water underneath the container is also an invitation for fungus gnats and some other houseplant pests to come and feast on your plants. 

Always check the soil before rewatering. Push the finger into it to check how moist is it. Keep the uppermost layer of your potting soil dry to deter fungus gnats from laying eggs and causing root damage.

Related: 10 Signs You Are Overwatering Your Indoor Plants

Closing Comments

Getting rid of fungus gnats can sometimes be a lengthy process, but if you are persistent enough, you can eliminate them for good. If you create a wise watering schedule, you’ll already be halfway to success, not only in the elimination of the adult gnats themselves but any chances of them appearing as well. 

I truly hope that these tips brought you some valuable insights into how to get rid of fungus gnats on house plants, how to control gnats, and how to keep your environment unattractive to them!

If you have some additional tricks or tips on the matter, don’t hesitate to share them with me in the comments section below!