Fungus gnats are pesky little bugs that can live in the soil of your houseplants.
If you have ever had a plant with fungus gnats, then you know how frustrating and annoying they can be. These little bugs can fly around your head and make it impossible to enjoy your plants.
There are several ways to get rid of fungus gnats, and in this blog post, we will teach you about the different methods so you can choose the best one for you.
We will also provide tips on how to prevent fungus gnats from infesting your plants in the first place.
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What are fungus gnats?
Fungus gnats are small, dark-colored flies with long legs and wings. They are very small with the adults being, at most, 1/8 of an inch long.
Fungus gnats are most often found in damp, poorly-drained soils.
The flies lay their eggs in the soil, and the larvae hatch and feed on organic matter in the soil, including roots and fungi.
How do fungus gnats get in houseplants?
Fungus gnats are most often introduced into the home through new plants or potting soil.
Unfortunately, it doesn’t matter what potting soil you buy, any brand can have fungus gnats.
I personally have gotten fungus gnats multiple times from the potting soil I have bought. I’ve tried multiple brands and all have given me fungus gnats.
Are fungus gnats harmful to plants?
Fungus gnats are mainly a nuisance, but in large quantities can lead to plant damage.
The stage that you see, adult fungus gnats, are not harmful to the plant at any time, but they can lead to damage. This is because, according to Wisconsin Horticulture, the females can lay up to 200 eggs.
Those eggs hatch into larvae, and the larvae of the fungus gnats could feed on the roots of your plants. They start out feeding on decaying organic matter and fungi that are naturally in the soil.
This doesn’t harm your plant, but if you get too many larvae, they will eventually start to feed on the plant roots, which can damage the plant.
Are fungus gnats harmful to people?
Fungus gnats are not harmful to people or animals, but they can be a nuisance.
The adult flies are attracted to light and have a tendency to fly around people’s heads or into their drinks.
This can be annoying, but fortunately, the fungus gnats do not bite or sting.
How to get rid of fungus gnats
There are several methods for getting rid of fungus gnats, but the most important thing is to let the soil of your plants dry.
Hydrogen peroxide
One way to get rid of fungus gnats is to use hydrogen peroxide.
To do this, mix one part hydrogen peroxide with four parts water and pour it into the soil of your plant. You want to make sure you get the soil wet all the way through.
The hydrogen peroxide will kill the larvae and eggs of the fungus gnat.
While this method does work there are a couple of issues with it.
Wet soil
The first issue is that the soil ends up very wet, which can cause problems on it’s own.
Some plants will get more stressed by wet soil than they were from the fungus gnats.
Kills the beneficial bacteria
The second problem is that hydrogen peroxide can kill the beneficial bacteria in the soil.
Killing the beneficial bacteria in your soil means your plants won’t get any of the benefits from them.
Let the soil dry out
The best way to get rid of fungus gnats is to let the soil of your plants dry out.
Fungus gnats need moist soil to survive, so by letting it dry out you are taking away their food source.
To do this, you want to water your plants less often and make sure the pots have drainage holes so the water can drain out.
You also want to make sure you are not overwatering your plants.
If you think you are overwatering your plants, check the soil before you water it. The soil should be dry at least an inch down before you water it again.
Repot the plant
Another way to get rid of fungus gnats is to repot the plant.
When you repot the plant, you want to make sure you use new potting soil. If you use old potting soil, there is a chance you will just end up with fungus gnats again.
You also want to make sure you are using a clean pot, or that you clean the current pot before putting the new soil back into it.
There is a risk with this one that you will be using soil that has fungus gnat eggs in it and will only see a brief break from the gnats.
Yellow sticky traps
You can also use yellow sticky traps to help get rid of fungus gnats. Adult fungus gnats are attracted to yellow and get stuck on the super stickiness of these traps.
To use these, just peel the paper off of both sides of the sticky trap and put the nonsticky side into the soil at the base of your plant.
When I’ve used these, I’ve had fungus gnats land on them within a few minutes. The yellow sticky traps I bought on Amazon say they are good for two to three months or until more than half the trap is covered in bugs or dust.
You can also buy them at some garden stores.
Cinnamon
Cinnamon, sprinkled on top of the soil, is another method to get rid of fungus gnats.
Cinnamon is a natural fungicide and helps to control fungus gnats by destroying the fungus the larvae feed on.
To use this method you need to sprinkle enough on top of the soil to get a visible layer and repeat every couple of weeks.
You will also want to bottom water during this time, otherwise, the cinnamon may get nasty and moldy.
Apple cider vinegar trap
You can also make a trap using apple cider vinegar and dish soap in a deep bowl or jar.
To do this just pour apple cider vinegar into your container until it is about a quarter to half-inch deep. Then add a few drops of liquid dish soap and stir it. Cover with plastic wrap or clear tape, leaving a small opening.
Alternately, you can just poke some holes in the plastic wrap with a toothpick. Make the holes big enough for the fungus gnats to go through, but not so big that they can fly back out.
Finally, place it near your plant. The gnats will be attracted to the smell and will fall in. Once they fall in, they won’t be able to get back out and will drown.
Change the solution every few days or when it gets full of gnats.
Neem oil soil drench
If you want to use a more natural product, you can use neem oil. Neem oil is a natural insecticide and will help to get rid of fungus gnats.
To use this method, you need to make a neem oil soil drench. To do this, mix one tablespoon Neem oil and one teaspoon of dish soap (or castile soap) with one quart of warm water.
Make sure to mix well and use right away. Neem oil starts to break down once it’s mixed with water, so only mix up what you will use.
According to Plant Care Today neem oil contains a compound called Azadirachtin which is a natural pesticide. It works by acting as a growth inhibitor and appetite suppressor.
Mosquito bits
Mosquito bits are small pellets that you can sprinkle on top of the soil to help get rid of fungus gnats.
The mosquito bits contain Bti, which is a bacteria that is deadly to fungus gnats (and mosquitos) but harmless to other living creatures.
The Bti will kill the larvae and help to control the population of fungus gnats.
If you don’t want to sprinkle the bits on the soil, they can also be soaked in the water you plan to use for watering your plants. To do this take a quarter cup of mosquito bits and mix them into 1 gallon of water.
After 30 minutes, scoop the bits out and use the water within 2 days. Repeat weekly for 3 weeks. Make sure to stir the water before using it to ensure it is mixed evenly.
If you don’t want to deal with the mess of scooping the bits out after soaking, place them into a fine mesh bag or nylon stocking before soaking them.
You can find mosquito bits at most garden stores or online.
Use insecticides
If you have a heavy infestation of fungus gnats, you can use an insecticide. Most home insecticides will kill the adults, but they may or may not help with the eggs and larvae.
I, personally, prefer to use any other method before resorting to insecticides. I prefer to not use insecticides inside my house if I can avoid it. And many of the above methods work without resorting to harmful chemicals.
How to stop fungus gnats from spreading to other houseplants
If you find fungus gnats in one houseplant you will want to do what you can to prevent them from spreading to more plants.
Fungus gnats are weak fliers and tend to stay close to their home plant. Use this to your advantage and separate the infected plant from other house plants.
You will also want to be extra vigilant in checking your other plants for fungus gnats. Be sure to check the soil and leaves for any bugs or larvae.
How to prevent fungus gnats
The best way to get rid of fungus gnats is to prevent them from infesting your plants in the first place.
Don’t overwater
The number one best way to prevent fungus gnats is to not overwater. Fungus gnats love damp conditions and will lay their eggs in wet soil.
Allow the top inch or so of soil to dry out between waterings. This will help prevent fungus gnats from infesting the soil.
Water plants from the bottom
Another way to help prevent overwatering (and, in turn, fungus gnats) is to water your plants from the bottom.
To do this, place your plant in a sink or shallow bowl of water and allow the water to soak up from the bottom. This will help to evenly moisten the soil without overdoing it.
It also prevents the top of the soil from getting too wet. Fungus gnats could still get into the plant through the drainage hole, but it’s a much smaller opening for them.
Use soil covers
If you live in a humid climate or tend to overwater your plants, you may want to consider using a soil cover.
A soil cover will prevent the fungus gnats from getting to the soil to lay their eggs. No eggs in the soil mean no larvae to worry about.
There are a few different types of soil covers you can use. One is to simply place a layer of gravel or sand on top of the soil. This will block the fungus gnats from getting to the soil while still allowing water and air to reach the roots.
Another option is to use insect-proof netting. This will also block the fungus gnats from getting to the soil while still allowing water and air to reach the roots.
Either of these options will help to prevent fungus gnats from infesting your plants.
Conclusion
Fungus gnats are small, flying insects that can infest houseplants. They are attracted to damp conditions and will lay their eggs in wet soil.
Fungus gnats are not harmful to humans or animals but can be quite destructive to plants. The larvae feed on the roots of plants, which can damage the plant and make it more susceptible to disease.
There are a few different ways to get rid of fungus gnats, including changing watering habits, using mosquito bits or sticky traps, and preventing them from infesting your plants in the first place.
No matter which method you choose, be sure to be diligent in your efforts. Fungus gnats can quickly become a problem in the home if they are not dealt with promptly.
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