What To Do if Your Plants Have Fungus Gnats

Over the past few years, I've developed a decent-sized plant collection. I started out with cactuses and succulents and eventually expanded to tropical plants. Going from having plants that rarely need to be watered to ones that actually need consistent watering has been a struggle for me. I'm always worried about my plants drying out and dying, so I end up giving them too much water. As a chronic overwater-er, my house is a fungus gnat's dream.

My fungus gnat problem became a huge issue a few weeks ago, and I couldn't ignore it anymore. Everything I saw online said to stop overwatering my plants, but it was a little late for that! I found some other good tips that I could try out and found another method on my own. I haven't seen a gnat in at least a week, so I think my infestation is over. I'm in no way a plant expert, but here's my advice for any plant parent dealing with fungus gnats:
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Buy Some Yellow Sticky Traps (and Skip the Vinegar)
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Image from Amazon product listing​

I've noticed multiple plant YouTubers using yellow sticky traps, so I decided to try them out. I was skeptical at first, but they really work! Fungus gnats are attracted to the color yellow, so they fly straight to the traps, get stuck and die. These traps come in different shapes and are very easy to find online. I saw sites mentioning making traps out of apple cider vinegar and soap, but I didn't have any and couldn't find anything answering whether or not other types of vinegar work. I tried making traps out of red wine and white vinegar, but those only caught a few gnats each. Plus, they were smelly, ugly, and a spilling hazard. I recommend just skipping the vinegar altogether and buying the sticky traps. They're pretty inexpensive (these are the ones I bought) and definitely worth it. 

The traps are great for catching adult gnats and seeing how bad your infestation is, but they won't kill eggs and baby gnats. If you have more than a few gnats, you'll need to do more to completely get rid of them.
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Repot Your Infested Plants
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Image from Clever Bloom

It seems drastic, but repotting your plants is a great way to get rid of fungus gnats. Fungus gnats lay their eggs in the moist soil of your houseplants (gross), which means getting rid of the dirt gets rid of the gnats. The eggs and larvae live towards the top of the soil, but instead of just scooping off the top, it's best to completely repot the plant to make sure you get rid of everything and provide new nutrients for your plant.

I was planning on switching to custom soil mix (that's a story for another day) around the time my gnat infestation happened, so instead of just repotting my most infested plants, I repotted nearly all of them. It took many hours over the course of a few days, but it was worth it. 

After having plants in the same soil for years, it can be hard to get rid of all of the old dirt, but I did my best and made sure to remove as much of the soil as possible, especially from the top. The new soil I'm using now is much better draining than what I was using before, so it should help prevent future outbreaks. You can use potting mixes designed for succulents or add either pumice or perlite to any bag of potting mix you already have for the same effect. To further prevent more nasty gnats from being born in your poor houseplants, I highly recommend listening to the next tip.
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Use Mosquito Bits
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Image from Amazon product listing​

This is another product I've seen multiple plant YouTubers using. I added a lot of Mosquito Bits (probably too many if we're being honest) to my potting mix and a little more to plants that I've seen gnats near. These little Bits kill the larvae, and thus prevent gnats from reproducing and continuing to fly around annoying you. They only work for a week or two, but will have done their job by then. Also, you can always add more to your plant pot as needed. I mixed the Mosquito Bits into my potting mix, but you can just sprinkle them on top of the soil. I went a little overboard because I was really freaking out about the gnats by this point.

The only issue with Mosquito Bits is they can get a little moldy when they get wet. If you see fuzzy white mold in your soil, don't freak out; it's not going to hurt your plants. I used a spoon to scoop off some of the mold and threw it away. When there was only a little bit, I mixed it into the soil. Fern from the Wildfern Youtube channel said she just mixes mold back into the dirt, and she seems to know what she's doing, so I listened to her.
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Doing all of this should be enough to get rid of your gnat problem over the course of a few days or so, but if you have a cluster of gnats, you might want to kill them right away.
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Spray Those Suckers With Raid 

Image from TOPBEST

Look, I know this sounds like a terrible idea, but by this point, I had been repotting plants for days and still had to repot my plants with the absolute worst infestations: a now deceased African violet (it was already dying by this point, I'll get to that later) and a ZZ plant. 

There were so many gnats crawling over the surface of the soil it was disgusting. I managed to repot the violet, but couldn't take it anymore when I went to do the ZZ plant. The ZZ plant was much bigger and had rocks and diatomaceous earth on top. I didn't want to throw away these nice rocks and was not too keen on picking them out with little gnats crawling over them, so I went looking for some insecticide. I found some old Raid for ants in my basement and decided it would have to do. I sprayed all over those rocks and immediately stopped seeing gnats moving around.
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After spraying the soil, I repotted my ZZ plant, doing my best to get rid of as much of the soaked soil as possible. That was over a week ago, and my plant looks very healthy. I only did this because ZZ plants are very hardy plants and I have another one, so I wouldn't have been too upset if it died. The Raid didn't seem to harm the plant and definitely killed a ton of fungus gnats. I'm not sure if I would use something like this on a more fragile plant, but it should be fine in general. There are a ton of insecticides available online and in stores that will work just as well as the one I used.

Neem oil is commonly recommended for killing pests, but I have never used it and am unsure of how well it works. Neem oil is kind of expensive, but would probably be a good option for people who want to avoid using harsh chemicals. 
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What About Diatomaceous Earth?
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Image from Succulent Alley

I'm not going to beat around the bush: I highly recommend that you do not use diatomaceous earth on your plants, ever. It seems like a good alternative to chemicals and/or highly visible traps, but it's not worth it. This white powder does work for killing insects when you sprinkle it on top of your soil, but only when it's dry. When I first tried using this, it worked pretty well, and I didn't see any gnats for a while. When I started watering the plants with diatomaceous earth on them, it turned really gross and ended up making my gnat problem infinitely worse.

When the earth gets wet, it all gloops together and ends up keeping the soil underneath super moist. This is the perfect environment for both fungus gnats and root rot. Maybe I used too much diatomaceous earth, but either way, it would have stopped working after getting wet. It's best to skip this and try using the methods I mentioned above.
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Don't Be Lazy​
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As soon as you start seeing gnats, you should do everything you can to get rid of them before it becomes a massive issue. Even better, you can try to prevent fungus gnats before you even see them. I tried to ignore the first few fungus gnats I saw, ​and eventually it became a full-on infestation. I also didn't do anything to try to prevent them, mostly because I didn't know much about them.

When you buy a new plant, you should remove the top layer of soil just in case it harbors gnats or other pests. I'm not going to tell you not to overwater your plants because no one does it on purpose. If you think you might be an overwater-er, you should pot your plants in airy soil and make sure all of your pots have drainage holes. You can also try bottom watering your plants, but if you do that, make sure you occasionally water from the top to wash away any salt built up in the soil.


I hope this post has been helpful for my fellow plant parents! If there are any new developments with my war against the fungus gnats, I'll update this post.
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