How To Banish Gnats
Updated: Jul 13, 2020
There you are, watching your houseplants flourish under your care. One by one you add to your collection, creating a small jungle in your home. Your friends are impressed. You start to feel pretty good about yourself, then a gnat flies right into your face. Suddenly it doesn't seem like such a good idea to have pots of dirt in your home.
The first time I encountered gnats on my plants, I second guessed my entire houseplant hobby. I wanted to ditch the whole thing and collect botanical artwork instead. If plant collecting came with bugs - I was out.
You don't have to have an emotional bug crisis. These little black flies seem to show up out of nowhere, but the good news is, you can send them right back. You just have to know how they work.
What are these things?
Fungus gnats look a lot like fruit flies or miniature mosquitoes. If your houseplant has fungus gnats, you'll see tiny, slow moving black dots crawling on top of the soil and flying just above it. You might also see them hovering around your windows towards sundown, searching for light. If they seem to fly right into your face, you're not imagining it. They're after carbon dioxide that we exhale - how annoying.
Most of the time, these gnats are harmless. However, if they invade your houseplants in large numbers for a long period of time, their larvae will gnaw at delicate roots and damage your poor plants.
How do they operate?
The life cycle of a fungus gnat is short. In just three to four weeks they grow from egg to mature adult. The adults only live about 7- 10 days, but they lay eggs, and leave a new generation behind. When you set out to eliminate them, you have to keep the cycle in mind, and target both adults and eggs.
Why are they on my plants?
Fungus gnats love moisture. They hide out in small pockets in the soil, or between planters and wet drainage trays. They feed on organic matter, and if your soil mix contains a moisture retainer like peat moss, you've basically set out appetizers for them. *Note: If you use soil amendments to retain water, you may want to mix in some diatomaceous earth for gnat prevention.
Search the internet and you'll find a variety of different ways to get rid of fungus gnats. You can D.I.Y. your heart out making homemade vinegar traps, mosquito bit tea, custom sized potato slices, and special sand topping for your soil, but who has time? I've beat fungus gnats using these quick and easy steps below. So can you.
Here's how to get rid of them.
1) The "Do Nothing" Technique - For a few plants, with a few gnats.
Gnats love moisture, so if you let your soil dry out, their party is over. If you water your plant about once a week, wait longer. Don't torture your plant, but go as long as you can before watering. Gnats feed and multiply in the top two inches of soil. If that layer of soil is dry, they won't loiter. Make sure to check underneath the pot, too. They can breed underneath your pot just as well as on top. *Note: this technique works best for a small plant collection with the same watering frequency. In a larger collection, gnats will simply hop over to a neighboring plant with more moisture.
2) Sticky Stakes - For a few plants with many gnats.
Cruel and unsightly, but effective - Sticky Stakes are basically, fly tape on a stick. Designed for houseplants, these small stakes go right into your soil and hold bright yellow fly tape just above the soil like flags. Gnats are drawn to the yellow and fly right into the tape, where they struggle and die - sorry gnats. It's heartless, but anything to protect your beloved houseplants from harm. These traps catch the adult flies, but not the eggs, pupa, or larvae, so you'll need to let the soil dry out along with using these traps.
3) Peroxide & Water - A safe way to kill the next generation.
Mix 1 part hydrogen peroxide with 3 parts water. Use this 1/3 blend to water your plants as you normally would. The solution will kill the eggs, larvae, and pupa and basically sanitize your potting soil. You'll hear some fizzing and see a little foam. It might seem risky to water your plants with hydrogen peroxide, but as long as the ratio is correct, it's totally safe. If you're worried about using this solution on a delicate plant, you can always dilute the mix a bit. Use all three tactics to eliminate gnats for good.
Nature is nature.
At the end of the day, it's good to remind yourself that plants aren't just home decor. They are a part of the natural world that we've brought inside. Any dedicated houseplant collector will have to deal with a few bugs now and then, but if you understand how they work and what keeps them away, you'll be able to prevent them from setting up shop in your beloved houseplants.