How To Get Rid of Fungus Gnats (2022 Edition)

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Fungus gnats are tiny flying insects that infest houseplants. They feed on fungus and mold, making them incredibly obnoxious during the hot summer months.

This expert guide to fungus gnats will show you:

  • How To Get Rid of These Annoying Pests Without Harming Your Plants
  • How To Prevent Fungus Gnats From Coming Back
  • How To Tell the Differences Between Several Flying Insects
  • What To Look For When Determining if You Have a Gnat Problem
Reviewed By:
Ed Spicer

Ed has been working in the pest control industry for years helping 1,000's of homeowners navigate the world of insect and rodent management. He manages Pest Strategies now helping homeowners around the world!

Table of Contents

    How To Get Rid of Fungus Gnats

    Fungus gnats are primarily houseplant pests. For that reason, it’s best to eliminate them using the mildest means possible. Here, our experts show you how to do that quickly and safely.

    1. Changing the Potting Mix

    Fungus gnats feed off of fungus and mold buildup within potting soil and plant roots. These conditions get worse during the summer months when there is a tendency toward overwatering.

    We advise changing the plant’s soil occasionally according to the seasons to discourage mold and fungal growth. For example, during warm seasons, switch from a soil-based potting mix to a courser blend containing the following ingredients:

    • Fir bark
    • Sphagnum moss
    • Charcoal
    • Perlite
    • Coconut husk chips

    You can mix and match as necessary to fulfill the moisture requirements of your plants. Then, when the summer ends, and you start watering less, change back to a higher density soil mix.

    When replacing potting soil, it’s vital to ensure that other plants do not become infested. Take these steps to ensure that does not happen:

    1. Use a dedicated table or workstation, preferably outside the home, to perform this function.
    2. Try to get as little of the old potting mix as possible on the table by catching it with a plastic trash bag.
    3. Throw the trash bag away immediately to avoid contaminating other plants.
    4. Remember to carefully inspect the new plant media before using it. Insects can contaminate even the newest retail products.
    5. Use only newly washed pots for transplanting.
    6. Be sure to wipe everything down with a solution of bleach and water when you’re finished.

    2. Vacuuming

    Simply vacuuming up the gnats on the leaves and stems of your houseplants can help. Still, it’s crucial not to suck up the potting soil in the process.

    3. Spray Treatments

    Commercial aerosol sprays utilize pyrethroid insecticides to get rid of gnats. You spray them directly on the plant or into the soil.

    The downside to using these products is the risk of poisoning the plant. For that reason, it’s crucial to read the label instructions carefully before using them.

    4. Vinegar Traps

    Another way to kill fungus gnats is to trap them. You can quickly put together simple vinegar traps by following these four easy steps:

    1. Fill four or five small sauce cups with water
    2. Add two drops of dish soap to each one
    3. Add a splash of apple cider vinegar (one part vinegar to two parts water)
    4. Stir the mixture thoroughly

    Place each dish where you see gnats and other flying insects. The dish soap traps the fungus gnats while the apple cider vinegar quickly kills them. When the container is full of gnats, simply empty it and start over.

    5. Sticky Traps

    Yellow sticky traps are ideal for trapping gnats permanently. Many of them come with a stick or stand to prop them up for maximum effectiveness.

    You can sometimes use traditional flypaper traps, but these are not as effective since most lack the yellow attractant. Also, they’re more challenging to work with, so it will be nearly impossible to remove them if they become stuck to the plant.

    6. Biological Controls

    Bacillus thuringiensis israelensis (BTI) is a bacteria that eats the larval stage of fungus gnats. It comes in products often dubbed “mosquito dunks” or “mosquito bits.” They’re typically in granular form and can be used for gnats or mosquitoes to disrupt their life cycles.

    To use, follow these steps:

    1. Apply four ounces of granular BTI to one gallon of water
    2. Let soak for 30 minutes
    3. Scoop the floating granules from the top to remove them
    4. Stir the water thoroughly to ensure a proper mixture
    5. Apply the water to the soil of your indoor plants

    This treatment typically kills fungus gnat larvae on contact. While there is some residual effect, it’s advisable to perform a follow-up treatment within seven days.

    Other DIY methods

    1. Hydrogen Peroxide

    The chemical action of hydrogen peroxide kills gnats and other small, flying insects efficiently. It also has the added benefits of removing bacterial and fungal growth while oxygenating the soil.

    To apply, first mix one part hydrogen peroxide to four parts water. Then, water your plants with the solution one time. However, it may be necessary to repeat the process until you see results.

    2. Neem Oil

    Neem oil comes from the seeds of neem trees. You can use it as a natural pesticide, and it’s safe on most types of plants. With that said, you should still read the label directions thoroughly to determine if your plants are suitable for spraying.

    3. Diatomaceous Earth

    Diatomaceous earth is a compound mined from dry lake beds. It contains diatoms that dehydrate insects, eventually killing them.

    While diatomaceous earth works well within dry spaces, it may turn to mud on the soil surface, causing it to become ineffective. For that reason, it’s best to apply it to dry top layers only.

    Check out this video for more tips on getting rid of fungus gnats:

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    How to Prevent Fungus Gnats

    Now that you have eliminated those pesky gnats from your home, it’s time to ensure they never come back. Here are four giant steps you can take to do just that.

    1. Change Plant Media Often

    Fungus gnat larvae use fungus, mold, and other organic matter as regular food sources, damaging your potted plants. By replacing the plant media regularly, you reduce the risk of mold and fungus growing within the pots.

    2. Avoid Overwatering

    Avoid drenching your plants with water during the summer months. Instead, try using a watering schedule. A structured plan will help keep your plants healthy while preventing overwatering.

    3. Provide Drainage for Your Plants

    Water can build up in moist soil over time, but instead of keeping plants dry, it’s preferable to add drainage holes to the bottom of your pots.

    For plastic pots, carve out triangular openings every two inches to let the water drain. For ceramic pots, you can purchase plastic plant liners that already have holes in place.

    4. Fix Leaks Around the Home

    Flying insects are not confined to indoor spaces. Your fungus gnats probably came from outdoors in the first place. They simply found a comfortable space to relocate for a while.

    Consequently, it’s prudent to check for water leaks outdoors as well as inside.

    Not Disease Carriers

    Since fungus gnats are not parasitic, scientists do not consider these tiny insects disease vectors. Despite that, in large numbers, they can cause significant damage to houseplants by feeding on their root systems.

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    How To Identify Fungus Gnats

    While being able to identify a gnat problem is important, there is no need to pinpoint the exact species. Here we give you some basic characteristics of fungus gnats.

    Identification

    Adult fungus gnats are about 2.5 millimeters long. They have black heads, long legs, and are delicate in appearance.

    Fungus gnats are sometimes confused with fruit flies. However, the fruit fly is slightly larger, measuring about one millimeter longer than the fungus gnat. Also, fruit flies are mostly brown, whereas fungus gnats are all black.

    Life cycle

    Fungus gnat eggs are so small it’s impossible to see them without magnification. Females lay up to 150 of them on top of the soil in about one week.

    At temperatures above 75 degrees Fahrenheit, the eggs will hatch after about three days. From there, it takes about 14 days to emerge as an adult. This period gives the larval stage plenty of time to cause considerable damage to your plants.

    Not Disease Carriers

    Since fungus gnats are not parasitic, scientists do not consider these tiny insects disease vectors. Despite that, in large numbers, they can cause significant damage to houseplants by feeding on their root systems.


    Signs & Causes of a Fungus Gnat Infestation

    Here are some of the signs and symptoms of a fungus gnat problem. Keep in mind that each plant type will show evidence of fungus gnats in its own way.

    Large Numbers of Gnats

    Finding large numbers of gnats flying around in your living room may signal it’s time to do something about these hungry plant pests. And it may also be worth it to take a look outside.

    Indoor infestations could signal a more significant problem around the entire perimeter of your property.

    Wilting, Discolored Leaves

    The larval stage of insects feeds on plant roots. The result is damage to the root hairs, causing leaves to turn yellow and discolored.

    Stunted Plant Growth

    Young plants are especially vulnerable to insects. Therefore, it’s important to inspect the soil immediately as soon as you notice stunted plant growth.

    Foliage Loss

    Leaves dropping off plants means that your fungus gnat infestation has reached a critical stage. While the plant can often be saved, it may become so compromised that the only thing to do is discard it. While this may seem like an extreme measure, it will protect other plants from becoming infested as well.


    A Final Word on How To Get Rid of Fungus Gnats

    Whether in your home or around your garden, fungus gnats can take over your plants within a matter of days. Likewise, if left untreated, they can eventually kill them.

    While home remedies are valid, it sometimes takes expert advice from a licensed pest control company to eliminate these unwanted guests. Their trained technicians can help you with the most pressing pest problems like fungus gnats. Also, they know how to incorporate certain pesticides that you may not want to handle.

    The first thing to do when hiring an exterminator is to consult the Better Business Bureau. Also, check online review sites to learn about previous customer experiences. Lastly, make sure the company you choose is fully insured in your state, protecting you from any accidental damages incurred during the treatment visit.

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