Fungus gnats are the last thing any farmer or gardener wants to see during their daily check. They can affect how your plant behaves, stunt its growth, and make for unwanted pests in your home or outdoor sanctuary. Every gardener knows there are such things as “good pests,” but fungus gnats aren’t one of them.
Here are 7 strategies for dealing with fungus gnats in your soil:
- Sprinkle neem oil.
- Top dress your soil.
- Use hydrogen peroxide.
- Set up sticky traps.
- Set up liquid traps.
- Try a nematode soak.
- Repot your plant and sanitize soil.
Below, I’ll take you through everything you need to know about how to deal with fungus gnats using the above suggestions. Afterward, I’ll provide some more information regarding the phenomenon, the importance of getting rid of it, and the measures you can take to stop it from happening again.
1. Sprinkle Neem Oil
Neem oil is a long-used natural method to get rid of pests. Master gardener Ron Finley suggests using neem oil in his Master Class. You should always have a little neem oil on hand because it naturally provides a plethora of benefits to your plants. It can act as a fungicide as well.
To use neem oil, you’ll want to combine it with a little bit of water and liquid soap (which helps it stick to the plant rather than just slide off). You can do this by using a spray bottle to make the application more accessible, or do it in a cup where you can dip a Q-Tip or paintbrush in.
Then, you’ll want to apply this mixture to your plants. Do this a little at a time at first and check back with your plant. As long as it took to the small amount without wilting or showing any damage, you can apply a more significant amount on your second go-around.
You can find neem oil in your local grocery store or bigger department stores. You can also order neem oil online.
2. Top Dress Your Soil
Top dressing your soil is a great way to soak up moisture and prevent fungus gnats from maturing past their larvae stage. To top dress, you can add a layer of mulch or new soil on top of the layer you already have (as long it’s not from the same bag of topsoil that gave you an infested plant!).
To be fair, this can be a difficult task if you’ve already got lots of larvae in your plant or many gnats flying around. Top dressing will help the first few inches of soil dry out, absorbing all the moisture. Without moisture, the larvae within the plant won’t be able to survive, and any remaining eggs won’t hatch. However, your plant may have a hard time bringing in moisture, too.
For this reason, using top dressing will work best if you combine it with some of the other methods listed on this article. Using a sticky trap or sprinkling some neem oil could perfectly complement this approach. The good thing about going the top dressing route is it may deter the still-flying gnats from laying eggs in the same pot.
When you top-dress your soil, it encourages bugs to go elsewhere. However, be cautious, as they might find somewhere else to lay their eggs if you don’t have them sticky-trapped. That’s why plant isolation is essential!
3. Use Hydrogen Peroxide
Hydrogen peroxide is another natural remedy to fungus gnats and other bugs. The EPA has approved hydrogen peroxide for controlling microbial pests on plants, whether they’re indoors or outdoors. It can work as a fungicide, too.
Using hydrogen peroxide will require going through a similar process to using neem oil. You’ll dilute a small amount of the compound with a large amount of water and a little bit of dish soap to help it stick to the plant. Then, you can apply it to the plant via a spray bottle or with a Q-Tip or paintbrush. You can grab hydrogen peroxide at any grocery store.
If you’ve got a food crop infested with fungus gnats, you can opt for a food-safe peroxide. These usually have a lower percentage of peroxide versus the one you may have in your first aid kit or bathroom cabinet. The HP Food Grade by Essential Oxygen (available on Amazon.com), for example, is 12% compared to your typical 35%.
4. Set Up Sticky Traps
Sticky traps aren’t the most aesthetically pleasing, but if you use them for a week or two, it’ll be worth not having fungus gnats flying around your home.
Fungus gnats living inside your house are likely to travel from one plant to another or hang out by windows if they have nowhere to lay their eggs. This is why they can become such a big problem within a short time. While outside, they can fly out to another garden and find moisture elsewhere; in your home, they’re trapped and make do to lay their eggs.
I wouldn’t suggest sticky traps for outdoor use because they might deter some garden-happy plants or more appealing insects from hanging out. You won’t get the bees or butterflies pollinating your garden and may accidentally harm some ladybugs. However, indoors, traps should do the trick.
If you’re squeamish, sticky traps might be hard for you to get behind. The results are worth it, though! To use a sticky trap for fungus gnats, you’ll want to hang it right near your plant or get the kind that you can stick right in the soil.
5. Set Up Liquid Traps
If you can’t wrap your head around touching a stick trap and throwing it in the garbage you’re not alone. Some people can feel extra squeamish around bugs, making sticky traps their worst nightmare. Liquid traps are another viable option.
There are many types of liquid traps, and most can be homemade. The water and dish soap trap has been proven effective for fruit and regular flies. This video by Tracie’s Place gives a recipe for liquid gnat traps:
In her video, she uses a combination of dish soap, water, and apple cider vinegar. In a small container, she combines the ingredients and covers them with plastic wrap. Then, she pokes a few small holes into the trap so that the gnats will get trapped when they fly in. She also suggests using a salt and pepper shaker if you have one.
This method will be beneficial if you have gnats all over your house. You can make a few liquid traps and set them in each room. These are less obvious than a stick trap and much easier to store away if you want them hidden from guests. Additionally, it may be more palpable for you to get rid of a liquid filled with gnats rather than touching and throwing the sticky traps away.
6. Try a Nematode Soak
Ever heard of fighting fire with fire?
I’ve been talking a lot about possible solutions for those who are squeamish around bugs; however, if you don’t care much either way, you can try a nematode soak.
Soil nematodes are tiny worms that can help consume bacteria, eat fungus, and eat smaller organisms. Additionally, they can eat any organic matter within a plant that may be harmful, like fungus gnat larvae. They don’t harm people or plants, either.
Where does one get nematodes? You can get them from some garden supply stores, pet stores or order them online.
7. Repot Your Plant & Sanitize Soil
Some may choose to get rid of the infested plant, especially if it keeps sprouting out more and more bugs. While this is certainly an option, if the plant is sentimental or you need to hold on to it, you can try a good old repot. Repotting your plant may be an excellent final step, even if you have gotten rid of the fungus gnats to the best of your knowledge.
Remove your plant from the contaminated pot, try to get as much excess soil as you can off of its roots, and add it to fresh, clean soil. You don’t have to get rid of the pot, but you should wash it down with a little bit of diluted bleach, neem oil, or hydrogen peroxide.
Then, you should either get rid of your soil or sanitize it. You can sanitize soil by heating it to no more than 180 degrees Fahrenheit (either in the microwave or an oven, one batch at a time) or freezing it. Additionally, some gardeners like the boiled water method and will boil a pot of water to pour over the soil to kill anything living in it. Both these methods will inhibit life in the plant, good and bad.
What Are Fungus Gnats?
Now that I’ve covered the most effective ways to get rid of these pests, it’s time to get a better grasp of the issue you’re dealing with. What is a fungus gnat, and how does it cause harm?
Fungus gnats are tiny insects that can infest your soil. They look like tiny black gnats, similar to fruit flies you might find flying around your bananas. The larvae of fungus gnats feed on plant roots.
Fungus gnats are harmless to humans, but their tiny larvae are laid deep in the soil and eat on small roots in your plant. This can lead to stunted growth, wilting, or even death for your houseplants.
How To Know If It’s a Fungus Gnat
If you’ve brought a new plant home and have found minor bugs flying around it as soon as you step through the door, you likely have fungus gnats. They have dark wings and can be anywhere from 1/16th of an inch (1.6 mm) to 1/8th of an inch (1.8 mm) long.
They look very similar to fruit flies or mosquitos and are commonly mistaken for them. Typically you’ll get rid of a fruit fly the same way you’ll get rid of a fungus gnat, so there’s no harm in making a mistake. However, the causes of their infestation are a bit different.
Commons Causes of Fungus Gnats
Fungus gnats could have hitched a ride on your plant when you got it from the store or the nursery. They are attracted to moisture and light, which is why they may be hanging out around your plants (because you are providing the plants with moisture and light). Many generations can grow within a year, meaning that infestations can quickly get out of hand.
The Importance of Getting Rid of Fungus Gnats
How should one deal with fungus gnats?
Fungus gnats aren’t the same as helpful ladybugs or beneficial fungus. As they lay eggs, their babies will continue to feed on the roots of your plants. Not to mention, I’ve never met anyone who enjoys having little swarms of bugs hanging out in their home.
Turning to pesticides might be your first thought, but pesticides can be harmful to your plants and aren’t something you want to spray without a second thought in your home. If the infestation has gotten worse, as it’s affecting your entire living space, you may need to call an exterminator.
However, if you’ve just got a few hanging out around your house plant, you can handle it on your own. The best way to deal with fungus gnats is to prevent them, but if it’s too late, you can isolate your infested plant, so the infestation doesn’t spread, and then you can try some of the previous methods to get rid of them.
How Can I Prevent Fungus Gnats?
The above methods can feel like a lot of work. You may be wondering if there’s a way to prevent fungus gnats altogether.
You can prevent fungus gnats by thoroughly inspecting any plant you are bringing home, being careful not to overwater, and being proactive if you do find one.
Below, I’ll discuss a few basic strategies for preventing fungus gnats.
Inspect Your Plants Thoroughly
Most of the time, fungus gnats were already on your plant when you brought it in. Someone rarely has an indoor garden and suddenly finds a fungus gnat infestation six or seven months after getting their last plant.
Thoroughly inspect plants before bringing them home. Even the highest-quality plant nursery in your area may have a fungus gnat or too lingering. Fungus gnats are especially prone to the plants you buy at grocery stores or department stores, where little attention may be paid to them.
I’ve been guilty of seeing a discount plant on a rack and taking it home with me just to find a fungus gnat infestation. If a plant is on sale, there may be a reason! Make sure to check your plant thoroughly.
Be Careful of Overwatering
Fungus gnats are highly interested in moisture, so they may float on over to your garden if your plants are exceptionally moist or grow a little bit of fungus. If you don’t have any fungus gnats inside your home, you don’t have to worry about this issue (but you should be a bit wary of fungus or waterlogging). However, with outdoor gardens, excess moisture might attract these gnats.
Nip The Problem in the Bud
Fungus gnats breed quickly and quickly create a full-blown infestation if you don’t tackle the problem right away. If you bring home an infested plant, don’t wait for it to become an unsolvable problem. Even one fungus gnat means there could be hundreds of larvae within the plant soil, eating at plant roots and ready to distribute their eggs throughout the rest of your house. Act quick!
Final Thoughts
Fungus gnats may inhibit or stunt your plant’s growth. They don’t harm humans or furniture, but they can infest a home quickly and become an unwanted pest in all of your plants.
To deal with fungus gnats, it’s best to attack early and eliminate them with one or two of the methods I’ve listed above.
