Homesteaders, greenhouses, and backyard gardeners all enjoy starting seeds from their favorite plants in late winter and early spring. All have a common enemy – fungus gnats. Whether you have one houseplant or hundreds of starter plants for the garden, fungus gnats can destroy all the work you have put into the plants unless the pests are controlled. If you are also searching for home remedies for fungus gnats, you’ve come to the right place.
Fortunately, you can control these destructive pests organically with hydrogen peroxide. It’s an easy and inexpensive way to prevent these tiny insects from destroying your plants. Just one application of a hydrogen peroxide treatment will typically end the life cycle of fungus gnats. It’s a safe and effective control method that will not harm saplings, garden plants, or houseplants.
Read on to learn what fungus gnats are and how to get rid of them efficiently and inexpensively.
What Are Fungus Gnats?
Fungus gnats are small flies that infest the soil, potting mix, and any other types of organic growing mediums used in containers to start seeds or grow plants. These small flies will also infiltrate other organic decomposition sources, like compost and plant material, and lay eggs.
Fungus gnat larvae feed on fungi and organic matter in soil and other growing mediums as they develop into adult gnats. The larvae will also chew on the plant roots and create problems for any container-grown plants in greenhouses, nurseries, and inside your home.
How does Fungus Gnat look like?
Fungus gnats are often mistaken for mosquitos and fruit flies. Adults are tiny, less than 1/8-inch long, with thin legs, antennae longer than their head, and light gray or nearly transparent wings. Fungus Gnat Larvae have a shiny black head and a long legless body that is clear or white. They feed on organic mulch, leaf mold, grass clippings, compost, root hairs, and fungi commonly found in or on top of plant growing mediums.
Fungus Gnats vs. Fruit Flies
Many people mistakenly identify Fungus Gnats as Fruit flies. Both are annoying, flying creatures that fly around the house. But they are different in appearance and their preference for the living environment.
Fungus Gnats
1. It looks like a smaller version of a Mosquito
2. Attracted to a moist soil environment
3. Mostly found in seed starting pots, indoor plants and compost piles.
Fruit Flies
1. It looks like a smaller version of a housefly
2. Attracted to decomposing or overripe produce and fruits
3. Mostly found near fruit bowls, kitchen sink, and garbage or trash cans.
How to identify Fungus Gnat infestation?
If the conditions of the growing medium or containers of organic matter are especially moist, or if there is a large infestation of fungus gnats, the larvae will leave slime trails on the surface of the growing medium that looks like trails from small snails or slugs.
Fungus gnats are attracted to light, and you may notice them flying around a lamp or window. These pests are weak fliers and never venture far from the soil they have infiltrated indoors.
They typically remain near potted plants. They can be observed running across or resting on top of the growing medium, plant foliage, compost, or wet mulch piles they have selected to call home.
Inspect plants at the nursery or garden supply center before purchasing them for any signs of pest infestation. If you bring home plants with fungus gnat larvae in the growing medium, it won’t be long before the larvae reach adulthood and lay more eggs in the potted plants you have at home.
How Fungus Gnats damage the plants
Adult fungus gnats don’t cause plant damage or threaten people or pets; they are an irritating nuisance. The larvae, however, can cause plant damage when present in large numbers. The larvae have a voracious appetite. After all the fungi and decomposing matter have been depleted from the growing medium, they will start chewing on the tender plant roots. The damaged roots can’t uptake nutrition and moisture for the plant. Thus the plant becomes stunted and cannot recover.
It is typically the case in seedlings and young plants. The infestation of fungus gnats larvae may not be noticeable until the young seedling is already damaged beyond repair. You may notice damage to an older potted plant before it reaches the point of no return. You can treat the soil with hydrogen peroxide to rid it of fungus gnats and larvae before it is too late.
Which Plants Are At Risk of Fungus Gnat damage
Vegetable plants, herbs, fruit plants, flowers, tree saplings, and houseplants are all subject to an attack from fungus gnats. The younger and more tender the plant is, like vegetable saplings started from seeds in the early spring, the more susceptible it is to a fungus gnat infestation.
These young plants typically have fresh, loose growing mediums that are easy for the fungus gnats to deposit their eggs into. The fresh growing medium is filled with the fungi and decomposing matter that the larvae need to feed upon. The looseness of the growing medium makes it easy for the larvae to wiggle around.
Females lay tiny eggs in moist growing mediums or organic debris so their larvae will have a rich food source as soon as the eggs hatch. Plants being grown in outdoor soil are rarely bothered by fungus gnats. It’s primarily the plants being grown in containers indoors at risk.
3 Hydrogen Peroxide Treatments to control Fungus Gnats
Most people have a bottle of hydrogen peroxide in their medicine cabinet at home. It’s a health and beauty product that has many uses and is very inexpensive. This foaming liquid is the most effective method to control fungus gnats, and it will not harm the plants or growing medium.
1. Hydrogen Peroxide to control Fungus Gnats on the indoor plants:
Step1: If an infestation is noticed, allow the top of the growing medium to dry out for a day or two before preparing the hydrogen peroxide treatment.
Step 2: Create a mixture of one part hydrogen peroxide and four parts water.
Step 3: Use this mixture to water the infested plant just like you usually would. Pour it onto the growing medium of every plant that has or potentially could have fungus gnats or their larvae.
The hydrogen peroxide and water mixture will foam and fizz a little when it comes into contact with the growing medium, but that is normal. It will kill fungus gnat larvae on contact. After a few minutes, the fizzing will stop, and the hydrogen peroxide breaks down into harmless oxygen and water molecules.
2. Hydrogen Peroxide Spray to control flying Fungus Gnats
Adult fungus gnats may be observed flying around the plant after the initial treatment. They will need to be disposed of before they can lay more eggs in the growing medium.
Step 1: Mix one part of hydrogen peroxide and four parts of water in a spray bottle.
Step 2: Lightly spray the plant leaves and stems where the adult fungus gnats are visible.
Step 3: Repeat as needed until the adults are no longer visible.
TIP: Hold a newspaper or similar item on the opposite side of the plant while applying the spray treatment to prevent it from landing on furniture or flooring.
In addition to this treatment, you can put Fungus Gnat traps near the base of the plant to trap the flying adult fungus gnats.
3. Hydrogen Peroxide Soil Drench for heavy infestation
If the infestation of fungus gnat is severe, you need to get rid of the baby gnats in soil (Fungus gnat larvae) or the growing medium along with the flying gnats. To make this indoor plant gnat killer:
Step 1: Stop watering the plant. Allow the growing medium to dry out slightly.
Step 2: Move the potted plant to the sink or outside so it can be drenched with the hydrogen peroxide treatment.
Step 3: Mix one part of hydrogen peroxide and four parts of water in a container.
Step 4: Saturate the potting soil with the hydrogen peroxide and water mixture until it freely runs out of the container’s bottom drainage holes.
Step 5: Wait for 10 minutes and repeat the step above once again.
This process will instantly kill the larvae and help flush the tiny dead carcasses out of the growing medium.
As a bonus, this flushing with hydrogen peroxide and water will remove any excess salt build-up in the growing medium caused by over-fertilizing the plant.
You may also wish to alternate Hydrogen Peroxide treatment with Neem Oil insecticide spray for maximum effectiveness in controlling fungus gnats.
How to prevent Fungus Gnat infestation from re-occurring
The treatment can be repeated as needed, but it typically only requires one treatment to rid the growing medium of larvae.
- After applying the hydrogen peroxide treatment above, help prevent future infestation by reducing the amount of water given to the plants.
- Fungus gnats thrive in moist, warm environments that are needed to promote seed germination and seedling development. Slightly reducing the amount of water given to the plant will make the growing medium a less inviting environment for the fungus gnat to thrive in.
- If the infestation is located in an outdoor compost or manure pile, treat the infestation with the hydrogen peroxide mixture until it’s saturated. Then let the pile dry out and stay as dry as possible.
- To prevent the gnats from being attracted to your potted plants by keeping the compost bin, manure pile, and other organic debris away from the greenhouse, container garden, house, or any other location where potted plants are grown.
- Don’t feed plants with excessive amounts of manure, blood meal, or similar organic materials that attract fungus gnats.
- Prevent the pests from coming indoors by keeping the doors and windows closed and sealing any cracks or tears in the screens or windows.
Related questions:
Life Cycle of Fungus Gnat
Fungus gnat life cycle has four stages -egg, larvae, pupa, and adult. The majority of its life is spent in the larvae and pupa stages. In 17 days, the eggs are laid in the growing medium, and the adults emerge ready to lay more eggs.
Fungus gnats can reproduce multiple times throughout the course of one year. The vast number of these destructive garden pests produce and reproduce if left uncontrolled. Their innumerable and destructive capabilities to plants are irreparable.
Where do fungus gnats come from?
Fungus gnats come into the house through open doors or windows. They may also come along with an infested potted plant. If you move outdoor potted plants inside for winter storage (like your potted Curry Leaf Plant), you may inadvertently bring in Fungus Gnat and their larvae into your home as well.
Is hydrogen peroxide organic or natural?
The chemical composition of the Hydrogen Peroxide molecule is H2O2. That means an extra oxygen molecule is joined to a water molecule. Although Hydrogen Peroxide sold in the stores is manufactured by chemical processes, Hydrogen Peroxide can occur naturally by sunlight reacting with water or as a byproduct of animal and plant bioprocesses.
In a small amount, it is safe to use Hydrogen Peroxide for plants in organic gardening. But do keep in mind that it can act as a bleaching agent and strip away organic components from the soil when used excessively.
Conclusion:
Daily observation and a little hydrogen peroxide can stop the damage caused by these pests before it can even get started. It’s incredible how you can control such a potentially harmful garden pest with an inexpensive and straightforward treatment of hydrogen peroxide. Hopefully, you won’t need to suffer these annoying creatures when you start your seeds indoors!
Have you tried this treatment in your home? Have any other ideas to get rid of Fungus Gnats? Please do share your thoughts with me by writing a comment below.
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I used 3% hydrogen peroxide on my Dracaena. I watered it until the water came out of the bottom of the pot and then redid it after 10 minutes. It was infested with fungus gnats. Incase any were still flying around, I covered the top of the soil with tape so they couldn’t get back in. When I went back to the plant after a week to treat it again, there were literally hundreds of gnats crawling all over the soil. I took the plant outside and again treated it with hydrogen peroxide twice. Everything looked good but after around 20 minutes, I noticed larvae and baby gnats coming out of the soil. There were a lot. I gave up. I’ve taken some cuttings from the plant and the pot with the soil in it is now behind my shed 😢
How to get rid of whitish build up on hydrangeas leaves
Hi Beverly! Have you tried using the Neem oil mix for plants? It is a safe and effective way to remove many of the insect and fungi problems from the plants.
– Gopi
Hello Gopi! Thank you for the great information. I recently started growing veggies, flowers and fruits in my grow tents. I noticed a seedling, that sprouted 2 days before the other flowers I planted that day, started to curl up and quit growing. I knew I had a small gnat problem but it was quickly turning into where I saw them in every planter. I let the soil dry a bit and I mixed a 3% hydrogen peroxide solution into a spray bottle. I am new so I did 1:5 because I did not want to damage the plants. I noticed in the vials that my girlfriend has in front of the window (it is a hanging rack with 3 rows of 4 vials to grow clippings of plants) that the hydrogen peroxide had broken up and oxygen bubbles were all over the roots. I am hoping the hydrogen peroxide helps the seedling breathe if I was suffocating it with over watering, which caused the gnats. Do you think my solution was strong enough? It only bubbled up on 1 cactus, out of 30 plants (cactus is mature, I am treating all my houseplants).
Thanks Again for the information,
Eric
Hi Gopi,
I am having issues with what appear to be small black Ant looking creatures on my Okra and Okra flowers. Are they a concern or should I not worry about it. They dont seem to do any harm.
It is common to see ants on okra plants. They don’t bother the plants, so no need to worry about it.
– Gopi
Hi there
Your information has been really helpful today! I’m becoming all too familiar with fungus gnats after an indoor infestation and now the perils of using too much neem oil spray on a cloudy day that turned sunny, which burned my tomato plant leaves in an attempt to cure early blight.
With that, can I use the hydrogen peroxide solution you suggest for the fungus gnats on vegetable plants? It seems the potting soil was infected with them (I thought I saw a larvae crawling, but took a chance – ugh!), so now I have them on my outdoor container plants. I used Mosquito Bits on the indoor plant which worked great (though only after 6 months of watering), but I can’t use that on my vegetables. I plan to try the neem oil soil soak for the gnats next!
Thanks again!
Question: Do you use regular old drugstore hydrogen peroxide in the brown bottles, or 3% food grade hydrogen peroxide for the fungus gnats??
PS LOVE your online info!! Very explanatory, and detailed info, thanx sooo much!
Hi Leah! Thank you for your kind words!
You can use any 3% hydrogen peroxide.
-Gopi
I have a small trick that seems to work. Remove the top layer of soil of the plants these gnats seem to love best. Use MG Indoor Potting Mix with a strong solution of concentrated Neem mixed in water and make it into a wet mud. Cover the top of the pot (I enjoy burying them alive) in the Neem mud and press it down firmly. The adults don’t seem to like it. I don’t think any newly hatched spawn can crawl through the layer either. I have 100 indoor plants in the nursery. Of those worst ones that I did the Neem Mud, they don’t seem to like it at all. I mist the mud with a Neem solution to keep it moist and they seem to move on.
Thank you! That’s a great tip!
-Gopi