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How to Save an Indoor Plant From Fungus Gnats

Andrea helps people design their homes and gardens. She likes to use Western Astrology and the Chinese Zodiac to help build templates.

Fungus gnats are annoying pests, but it is possible to get rid of them at an affordable price.

Fungus gnats are annoying pests, but it is possible to get rid of them at an affordable price.

Getting Rid of Fungus Gnats

Topping the list of annoying things that can happen to your plants would be a fungus gnat infestation. Fortunately, you can save most plants when this bug apocalypse happens. There are also affordable options to get rid of gnats, and you don't have to call in a pest technician.

In this article, I'm going to give you the following information:

  • Steps to take to save your plants from gnats
  • Tell you how to prevent the spread of a gnat infestation
  • Steps to take to prevent future infestations
  • Suggest actions and products to combat the problem

My philosophy when it comes to these tiny devils is to attack them with multiple strategies rather than a one-step method. My approach is aggressive. I'm not trying to save the bugs, I'm here to help you kill them and prevent them from coming back.

What Caused the Fungus Gnat Invasion?

The number one culprit of a fungus gnat invasion is overwatering plants. The best thing to do to curb the problem is to let the plants dry out before adding new water. Check the top of the soil with your finger. Is it wet? Then don't add more water.

Fungus gnats LOVE damp soil and decaying vegetation. It's important that your plants are in pots with good drainage. You need to stick to a watering schedule, and you need to pull back on watering your indoor plants.

First Steps to Eliminating Fungus Gnats

Before you take any plan of action, first inspect your plant. Is it overrun with gnats? Would you be happier tossing the plant in the trash or saving it? Those are important questions to ask.

Next, examine your room and find out where the gnats are coming in. Bugs love to come in through windows, cracks, and the like. Once you have identified their entrance, use a spray to knock them out. You can find an affordable spray at Home & Garden shops. It'll set you back $10 or so.

The other important thing to do is to reconsider how much and how often you water your plants. Use a moisture meter to test soil. If you have a fungus gnat invasion after using a moisture meter, then water your plants at a lower number than what is suggested for your plant's moisture level.

Pro Tips: Move infested plants away from flora that is happily gnat free. Place the infested plant somewhere else while you work with it to kill its unwanted bugs. You don't want the fungus gnats to spread to other plants and create a bigger problem.

When you buy a new plant, put it in an isolated area. Wait until you know it's free of gnats (or other pests) before moving it into a room with other plants.

Fungus gnats are small, black insects. They look like miniature mosquitoes.

Fungus gnats are small, black insects. They look like miniature mosquitoes.

Options for Removing Fungus Gnats

SolutionEstimated Cost

Pest Control Spray

$8-10

Hydrogen Peroxide + Water Solution

$1-6

Bottom Water Plants

FREE

Neem Oil

$6-20

Diatomaceous Earth

$10-30

Cinnamon

$2-11

Chamomile Tea

$2-8

Lavender, Spice/Dried/Flowers

$3-11

Lavender Tea

$2-11

Yellow Sticky Paper

$5-18

DIY Fungus Gnat Trap

You likely already have the items to make it at home

Store Bought Fungus Gnat Trap

$20-60

Dryer Sheets

$3-11

Sand

$6-15

Gardening Pebbles

$10-25

Adjust Temperature

N/A

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1. Hydrogen Peroxide

The next time you water your infested plant(s), use a solution of hydrogen peroxide and filtered water. My recommendation: Use a mixture of one part 3% hydrogen peroxide and four parts water.

Important: Make sure the soil has dried out before adding hydrogen peroxide.

Hydrogen peroxide is safe for plants. It actually promotes healthy root growth. The extra oxygen helps roots absorb the soil's nutrients. The extra bit of oxygen will help your plants to grow faster and healthier.

Don't Overdo Hydrogen Peroxide

Keep in mind that too much of anything can be a bad thing. 10% hydrogen peroxide is used as a weed killer. Don't use industrial versions of this product on your plants! The right amount of hydrogen peroxide will benefit your plants; the wrong amount will kill them.

Apply the correct solution once every 7-10 days for a small pot and 2 weeks for a large pot. Repeat the step until the fungus gnats are gone. The solution will kill larvae and eggs. Don't be afraid of the fizzing that comes from the chemical compound, that's what gets rid of the gnats.

You could put the solution in a water bottle and mist your plants with it.

2. Bottom Water Your Plants

Fungus gnats hang out at the top of your soil. They like to party in damp soil. If you water plants from the bottom, it will be harder for gnats to find damp soil. You'll have killed the party venue.

If fungus gnats can't find their ideal soil, they're less likely to reproduce.

3. Neem Oil

What is neem oil? It is an organic pesticide found in neem tree seeds. The oil is yellow to brown, has a bitter taste, and has a garlic/sulfur smell. Fungi and gnats find garlic and sulfur repulsive.

Neem oil is also called margosa oil. The tree is native to the Indian subcontinent. The species is also found in the tropics.

To combat fungus gnats: Dilute the oil with water. Follow the manufacturer's directions. Bottom water your plants with the solution, so it gets into the roots. You can also spray the solution on the top part of the plant and the soil to deter the gnats.

4. Diatomaceous Earth

What is diatomaceous earth? It's a powder made from fossilized algae found in water bodies. Dried sediment from the fossils is high in silica.

You can add DE in a couple of different ways: sprinkle it on top of the soil, or mix it into the soil mix if you repot the plant.

DE will kill larvae and gnats within a week. After three weeks, the gnat population should be gone. DE is extraordinary at liberating your plants from pests.

Important: Buy food-grade diatomaceous earth—not pool grade.

Cinnamon repulses fungus gnats.

Cinnamon repulses fungus gnats.

5. Cinnamon

A cheap item you can use to protect your plant from gnats is cinnamon. The spice is a natural and powerful fungicide. It's also good for your plants.

All you have to do is sprinkle cinnamon on the surface of your plant's soil. This will turn a "fungus gnat resort" into inhospitable real estate.

Cinnamon works on other fungal problems, so it's good to have this spice in your cabinet at all times just in case your plants get mold or have other issues.

The spice repels bugs. I've used it to prevent ants from getting into my cats' food. Insects don't like the smell of cinnamon. Cinnamon essential oils or strongly scented candles can help ward off unwanted bugs. Consider cinnamon for bugs like what garlic is to vampires.

In good news: Cinnamon is good for plants. Its antibacterial properties protect plants from diseases, mold, pests, and mildew. It also encourages root development. It's a good idea when adding a cutting to soil to sprinkle cinnamon on top.

6. Chamomile Tea

The tea known for its sleepy-time effect can put fungus gnats to rest for good. There are a couple of ways you can incorporate chamomile tea into your plant setup:

Option 1: Brew a quart of tea and add it to a 1-gallon container. Make sure the tea has cooled down and is weak. Mist or lightly drizzle the plants with it.

Option 2: Plant a tea bag in the soil.

Chamomile flowers are high in sulfur, and sulfur has been used as a fungicide for centuries. It will kill fungal spores and prevent diseases in plants.

7. Lavender

Bugs find the smell of lavender revolting. Fungus gnats don't like your lavender-scented shampoo or your lavender-scented dish soap. About the only bugs that do are bees.

You can repeat the same trick with chamomile tea with lavender tea. You can also place lavender flowers in your infested pots. You could also put lavender flowers near your infested plants.

8. Yellow Sticky Paper

A tried and true classic method for killing gnats: yellow sticky paper. This is affordable and you can find it at gardening stores. The process is simple: place the sticky paper in spots where the gnats travel. They'll get stuck and die.

Yellow is attractive to gnats, so they'll happily make their way to the color. Don't use the blue sticky paper; it's for different bugs.

I recommend first killing off the gnats at the roots with a spray. After you've contained the infestation, add yellow sticky paper in spots where you might have some rogue gnats that are still trying to figure out the location of the party.

9. DIY Fungus Gnat Trap

You have probably seen someone make one of these before—whether your mom, grandpa, or a smart roommate. It's essentially the same kind of trap you'd make for fruit flies.

In a small bowl, mix together warm water plus two tablespoons of vinegar or apple cider vinegar. Add a tablespoon of sugar and a dollop of dish soap. Stir everything together. The trap works better, in my opinion, if the bugs have to travel through a funnel to get to the vinegar solution. The gnats will drown in the solution.

10. Store Bought Fungus Gnat Trap

For those of you wanting to spend more money, or if you have a large plant collection and want extra protection, there are fungus traps you can buy off Amazon and at Home & Garden stores. These can get pricy—some have a price tag as high as $60. I don't think you necessarily need to shell out that much money to get rid of gnats, but that's up to you.

There are stylish plugins and electronic devices that can lure in and kill your unwanted bugs.

11. Dryer Sheets

A study at Kansas State University found that Bounce dryer sheets have properties that repel adult fungus gnats.

All you need to do is place the dryer sheets in and around your pots.

Pro tip: Placing dryer sheets intelligently in your closets and drawers can help keep other bugs away, like spiders.

I recommend placing lavender-scented dryer sheets around your plants. The study at Kansas State University found lavender and basil were the likely culprits that repelled the gnats.

Add pebbles to potted plants to keep gnats from getting to the soil.

Add pebbles to potted plants to keep gnats from getting to the soil.

12. Add Sand and/or Pebbles

Fungus gnats want to get to damp soil to lay their eggs. If you make it harder for the gnats to get to the soil, you'll have an easier time winning this battle.

You can still water your plants from the top if there is a layer of sand or pebbles. Some plants might even prefer it if there are stones with water droplets. This can make it easier for leaves to find water, and it can help put moisture into the air through evaporation.

Not all plants like sand, so read up on your plant before adding a layer of sand. Pebbles are easy to remove, sand isn't.

13. Gnats Can't Survive in the Cold

Fungus gnats are a summer problem. They thrive when it's 70 to 80°F. Once temperatures drop below 60°F, they die or disappear. If you have a plant that can survive in cooler temperatures, consider putting it in a colder spot in your house.

Gnats will be out of the equation come autumn, winter, and early spring. Gnats also have a hard time withstanding extreme heat. If you have an indoor plant that can tolerate the hottest days of summer, it might be smart to put it outside. Keep in mind a lot of plants are sensitive to excessive heat and intense sunlight.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Andrea Lawrence

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