Fungus gnats (also called soil gnats) are probably the most common (and annoying) houseplant pests. So, in this post, I’m going to tell you all about them, and show you how to get rid of them – FOR GOOD!
You will notice these indoor plant bugs crawling out of the potting soil, or flying around your plant when you water or otherwise disturb the soil. Yuck!
They are a very annoying pest, there’s no doubt about that! But the good news is that you can get rid of them, and keep them from re-infesting your houseplants.
Here’s what you’ll find in this detailed guide…
What Are Fungus Gnats?
Fungus gnats are tiny black flying bugs in houseplants soil. You will see them crawling around on top of the soil, or flying around your plants
Fungus gnats live and breed in the soil. Adult gnats will lay eggs in the soil, and the larvae (tiny white worms that are barely visible to the naked eye) will feed on roots and other organic matter in the soil.
Fungus Gnats or Fruit Flies?
Fungus gnats look similar to fruit flies, and I have seen many people mistaken a fungus gnat problem with fruit flies.
But they are not the same type of bug. Fungus gnats lay their eggs in moist soil where the larvae will hatch and feed on small roots, fungus and other organic matter in the soil. They have no interest in fruit.
Here’s a quick way to tell the difference…
- If you see tiny black bugs in plant soil, and flying around your plants – those are fungus gnats.
- The gnats that are flying around the fruit, or the garbage disposal in your kitchen are fruit flies.
If you’re still unsure, read about how to tell the difference between the two here, so you can make a positive ID every time.
Will Fungus Gnats Kill Plants?
The short answer is no, fungus gnats will not kill your houseplants. Fungus gnats are mainly just a nuisance and are rarely destructive to the plant.
Sometimes they can cause root damage if the infestation is heavy, but normally fungus gnats only eat rotting roots.
Even though they aren’t a huge problem for your plants, fungus gnats are likely to drive you crazy, right?! I mean, who want gnats flying all over their house? Not me!
So, let’s figure out how to get rid of gnats in plants… but first, it’s important to understand where they came from in the first place, so we can make sure they never come back.
Where Do Fungus Gnats Come From?
A fungus gnat infestation can come from anywhere. The most common ways fungus gnats get into your house are either they’re in the soil of a newly purchased plant, or in a bag of potting mix that you bring indoors.
But fungus gnats can also come in with a plant that was outside during the summer. Heck, they can even fly in through the screen of an open window or door.
How To Get Rid Of Fungus Gnats In Houseplants Soil
Fungus gnats are difficult to eliminate if you have a large number of indoor plants. The adults can easily fly or jump from one plant to the next, laying eggs wherever they find moist soil.
Like fruit flies, the adult fungus gnats only live for a few days. So, once all the larvae are dead, your fungus gnat problem will go away.
There’s no need to resort to toxic synthetic pesticides, fungus gnats can easily be fought using all-natural pest control remedies and methods. Below are the best methods to use to rid your indoor plants of those annoying flying gnats…
1. Control soil moisture
Fungus gnat larvae thrive in moist soil, and they can’t survive in dry soil.
So, the easiest and most effective method of plant gnats control, and ultimately eliminating fungus gnats, is to make sure you never overwater your plants.
Be careful though, you don’t want to allow the soil to dry out completely on most houseplants. Use a soil moisture gauge to help maintain the perfect level of moisture for your houseplants, and get rid of gnats in plant soil.
Indoor plant watering devices also make watering houseplants easier, and help you avoid overwatering so you can get rid of plant gnats.
2. Water plants from the bottom
Fungus gnat larvae live in the top inch of the soil, which tends to stay pretty moist when you water plants from the top.
Bottom watering plants will make it easier to maintain dryer top soil, without risking the overall health of the plant.
To water your plants from the bottom simply pour water into the plants drip tray or cache pot, and allow the plant to soak up the water through the drainage holes.
Never allow your plant to sit in water for too long. Dump out any remaining water after about 30 minutes of soaking.
3. Use yellow houseplant sticky stakes
Putting a yellow sticky trap near the plant is a super safe pest control method that will attract and capture the adult fungus gnats.
This will only be effective to control the adult population, it will not take care of the problem at the source (the larvae).
But yellow sticky traps definitely help to keep the adult fungus gnats from flying around to other plants.
4. Apply organic pest control products
Pour or spray an organic insecticidal soap or a neem oil mixture into the top of the soil to kill gnats in potted plants.
I make my own insecticidal soap by mixing using 1 tsp Dr. Bronner’s Baby-mild Liquid Soap to one liter of water.
Neem oil works great to kill houseplant pests, and has a residual effect that helps with prevention. You can buy neem oil here.
These natural gnat pesticide treatments should be effective after a few applications, just take care not to overwater your plants.
Related Post: How To Use Neem Oil As Organic Pest Control
5. Remove the gnat infested soil
Remove the top inch of potting soil and replace it with new, sterile potting soil.
This will remove fungus gnat eggs and larvae, and make it easier to gain the upper hand.
Just keep in mind that gnat eggs in soil could still hatch and mature after you remove it from your plant, so make sure you take it outside to the trash.
6. Use soil covers
This will help control gnats in soil, and deter them from laying eggs. Plus soil covers also add a nice decorative touch.
You could also use a gnat barrier top dressing, which is a non-toxic soil cover that is specifically made for eradicating fungus gnats.
7. Store unused potting soil in a sealed container
Open potting soil bags can also be a breeding ground for fungus gnats, so make sure you keep that in mind when storing unused soil.
I store all of my potting soil in buckets that have a tight fitting lid rather than in the bag it comes in. Fungus gnats can’t survive without oxygen.
8. Never reuse potting soil
I know it’s tempting to pinch pennies by reusing potting soil for indoor plants, but you’re just asking for trouble. Always use a fresh, sterile potting soil mix when repotting your plants.
In this section, I’ll answer some of the most commonly asked questions I get about controlling fungus gnats in houseplant soil. If you can’t find the answer here, ask your question in the comments below.
Will treating the soil hydrogen peroxide kill fungus gnats?
I’ll admit that I have never tried this method myself, but several of my readers swear by it. The common ratio I’ve been given is to mix 1 part hydrogen peroxide to 4 parts water. Use it to wet the top inch of the soil.
You can pour it in the soil, or spray it over the top. Keep in mind that this will only kill the larvae, and not the adult gnats that are flying around.
The most important thing to remember for eradicating fungus gnats is to control how much you water houseplants. Remember, fungus gnats live and breed in moist soil, and overwatering is the number one cause of houseplant gnats.
Even if you are successful in eliminating a fungus gnat infestation from your house, recurring problems are difficult to prevent. The good news is that fungus gnats are one of the easiest houseplant pests to control.
If houseplant pests are driving you crazy, and you want to learn how to get rid of plant bugs once and for all, check out my Houseplant Pest Control eBook! It will help you identify common houseplant bugs, and show you exactly how to kill them before they kill your beloved plants! Download your copy today, and get rid of bugs on houseplants for good!
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- How To Debug Plants Before Bringing Them Indoors
Leave a comment below and share your tips for how to get rid of fungus gnats in houseplants soil.