How to Get Rid of Fungus Gnats: A Comprehensive Guide to Protecting Your Plants and Home

There’s nothing more frustrating than tending to your beautiful houseplants or garden only to be met by the small, persistent buzzing of fungus gnats. These tiny pests, although not harmful to humans, can be a real nuisance and a potential threat to your plants. Fungus gnats thrive in moist soil and can wreak havoc if left unchecked. The good news is that there are plenty of ways to get rid of fungus gnats and prevent them from returning. In this guide, we’ll walk you through the signs of an infestation, where fungus gnats come from, and the most effective methods to rid your home and plants of these pests.

6 Ways To Get Rid of Fungus Gnats

If you’re already dealing with an infestation, don’t worry! You can effectively eliminate fungus gnats using a reliable fungus gnats remedy and a combination of methods. The purpose is to target both the adult gnats and their larvae in the soil to completely break their life cycle. Below are several methods to help you kill the gnats.

Neem Oil & Other Sprays

Neem oil is a versatile, natural insecticide that works wonders on fungus gnat infestations. It disrupts the life cycle of both adult gnats and larvae, preventing eggs from hatching and larvae from maturing. Here’s how you can use neem oil to control gnats:

Neem Oil Solution: Mix one to two teaspoons of neem oil with water and a few drops of dish soap to help emulsify the mixture. Pour or spray this solution directly onto the soil and the plant leaves. Make sure to saturate the top layer of the soil, where gnat eggs and larvae tend to reside.
Insecticidal Sprays: If neem oil isn’t readily available, other organic insecticidal sprays can also help. These sprays, available at most garden centers, often contain pyrethrin, a natural pesticide derived from chrysanthemum flowers that can kill adult gnats on contact.
Regular Application: For best results, apply the neem oil or other sprays every few days for at least two weeks. This will ensure that you catch any newly-hatched larvae or adults before they have a chance to reproduce.

Waiting Longer Between Waterings

One of the most effective and simplest strategies for getting rid of fungus gnats is altering your watering habits. Fungus gnats thrive in moist environments, so making adjustments can have a significant impact.

Let the Soil Dry Out: The biggest mistake many plant owners make is overwatering their plants. When soil remains consistently wet, it provides an ideal environment for fungus gnats to breed. By waiting longer between waterings and allowing the top 1–2 inches of soil to dry out, you can kill off larvae and discourage adult gnats from laying eggs.
Monitor Moisture: You can check moisture levels with a simple finger test or use a soil moisture meter to ensure you’re only watering when absolutely necessary. This not only helps eliminate fungus gnats but also promotes healthy plant growth.

Drench in Water

A water drench is an effective method to flush fungus gnat larvae out of the soil. Here’s how it works:

Prepare a Water Drench: Fill a basin or sink with water, and submerge the plant pot so the water reaches the top edge of the pot. Let it sit for about 10–15 minutes. This will force larvae to the surface or out of the drainage holes.
Drain the Soil: Once you’ve completed the water drench, allow the pot to drain thoroughly. Letting the soil sit in water too long can lead to root rot or more moisture problems, so make sure it dries out before the next watering.

This method works best when combined with other strategies, such as neem oil or sticky traps, to catch adult gnats and prevent further infestation.

Repotting

In severe cases of fungus gnat infestation, repotting your plants might be the most effective solution. When the soil is heavily infested with larvae and the problem persists, it may be best to start fresh with new soil.

Remove the Plant: Gently remove the plant from its pot, taking care not to damage the roots. Shake off as much of the old, infested soil as possible, and discard it.
Sterilize the Pot: Before repotting, thoroughly clean the pot with hot water and soap to kill any remaining fungus gnat eggs or larvae. You can also soak the pot in a bleach solution (1 part bleach to 9 parts water) for a few minutes to ensure it’s disinfected.
Fresh Soil: Repot your plant in fresh, sterile soil, and make sure to choose a well-draining potting mix. Adding some perlite or sand can improve drainage and reduce the likelihood of future gnat infestations.
Monitor Watering: After repotting, avoid overwatering, as damp soil is the primary attractant for fungus gnats. Keep a close eye on your plant’s moisture levels to prevent the problem from reoccurring.

Sticky Traps

Sticky traps are an excellent, non-toxic way to capture adult fungus gnats. These yellow, adhesive traps are widely available at garden centers and are easy to use.

How to Use Sticky Traps: Simply place a few sticky traps in and around your plant pots. Adult fungus gnats are attracted to the color yellow and will fly directly into the traps, getting stuck.
Placement Tips: Position the traps near the soil surface or hang them close to the affected plants. You can also cut larger traps into smaller strips and place them in different pots for more widespread coverage.
Replace Regularly: Over time, the traps will become covered in gnats, so be sure to replace them as needed. While sticky traps won’t eliminate the larvae, they help control the adult population and reduce the chances of future egg-laying.

Mosquito Dunks

Another effective solution for killing fungus gnat larvae is the use of Mosquito Dunks. These biological control discs contain a bacterium called Bacillus thuringiensis israelensis (BTI), which is deadly to the larvae of fungus gnats but safe for plants, pets, and humans.

How to Use Mosquito Dunks: Break a Mosquito Dunk into smaller pieces and soak them in water for a few hours. Use the treated water to drench the soil of your plants. The BTI in the dunk will target and kill the larvae living in the soil, halting their development.
Repeat as Necessary: For the best results, apply the BTI water once a week for a few weeks, or until the infestation is gone. Since the bacterium doesn’t harm adult gnats, combine this treatment with sticky traps or other methods to control the flying gnats.
Long-Term Prevention: Mosquito Dunks can also be used preventively if you’ve had problems with fungus gnats in the past. Applying a BTI water drench once a month can keep larvae at bay and prevent future infestations.

Signs of Fungus Gnats

First things first: how do you know if you’re dealing with fungus gnats? While these pests are small, they’re usually not hard to spot once they’ve made themselves comfortable in your plants. Here are some telltale signs of a fungus gnat infestation:

Tiny Flying Insects:

Fungus gnats are small, dark-colored flies, usually no bigger than a few millimeters in length. You’ll often see them hovering around your plants, especially when you water them or disturb the soil. They can be easily mistaken for fruit flies, but unlike fruit flies, they’re more likely to be found near soil than around food.

Wilting or Yellowing Plants:

While adult fungus gnats aren’t directly harmful to plants, their larvae can cause significant damage. These tiny worms feed on plant roots, which can result in stunted growth, yellowing leaves, or wilting.

Damp Soil:

If the soil in your plants is consistently moist, it can become a breeding ground for fungus gnats. Their larvae thrive in damp environments, and overwatering your plants could inadvertently invite these pests into your home.

Gnats Around Windows:

Fungus gnats are often drawn to light, so you might notice them buzzing around windows, particularly near plants that sit on windowsills.

Larvae in the Soil:

If you suspect fungus gnat larvae in your plant soil, gently move the top layer of soil aside. You might see small, translucent worms wriggling just beneath the surface—these are the larvae of fungus gnats.

Where Do Fungus Gnats Come From?

Understanding where fungus gnats come from is the key to preventing them. Fungus gnats are typically attracted to environments that are damp, dark, and rich in decaying organic material. This makes plant pots with moist soil the perfect breeding ground. But where exactly do they come from, and why do they show up in the first place?

Overwatering: One of the most common reasons for a fungus gnat infestation is overwatering plants. When the soil stays wet for too long, it creates the ideal environment for gnats to lay eggs, which quickly hatch into larvae and begin feeding on the organic material in the soil.
Potting Soil: Sometimes, fungus gnats come pre-packaged with your plants. Certain brands of potting soil, especially those rich in organic material like peat moss, can already have fungus gnat larvae in them when you buy them. If you’ve ever noticed gnats shortly after repotting a plant, this could be why.
Open Windows or Doors: Fungus gnats can find their way into your home through windows, doors, or cracks, especially if you’ve got houseplants nearby. Outdoor garden plants, too, can harbor these pests, and they can quickly spread indoors.
Decaying Organic Matter: Fungus gnats are also attracted to areas where decaying organic matter is present, which is often the case in soil that has been watered too frequently. If your plant soil is breaking down, it’s a prime spot for gnat eggs to be laid.

Now that we know where these pests come from, let’s talk about how to keep them away!

How to Prevent Fungus Gnats

Prevention is always better than a cure, and that’s certainly true when it comes to fungus gnats. The good news is that there are several simple measures you can take to stop these pesky insects from infesting your plants. Here are some effective prevention methods:

Avoid Overwatering: This is perhaps the most important step in preventing fungus gnats. Since gnats thrive in damp conditions, letting your plant soil dry out between waterings can go a long way in keeping them away. Stick your finger about an inch into the soil to check for moisture before you water. If it’s still damp, hold off on watering until the top layer has dried.
Use Well-Draining Soil: When planting or repotting, make sure to use a potting mix that is designed for good drainage. Soil that retains too much water can create the perfect breeding ground for fungus gnats. Adding materials like perlite or sand to the mix can improve drainage and help keep the soil dry.
Remove Decaying Plant Material: Dead leaves or other organic matter sitting on the soil’s surface can attract fungus gnats. Regularly check your plants for dead leaves or flowers and remove them promptly. Keeping the soil surface clear of debris is a simple but effective prevention method.
Let the Soil Breathe: Aerating the soil regularly by gently disturbing the top layer can help dry out the soil more quickly. This reduces the dampness that attracts fungus gnats and discourages larvae from thriving near the surface.
Use Yellow Sticky Traps: These traps are designed to catch flying insects, including fungus gnats. Placing sticky traps near your plants can catch adult gnats before they have a chance to lay eggs. You can find these traps at most garden centers, and they’re a chemical-free solution to keeping gnats at bay.
Use Bottom Watering for Plants: Instead of watering your plants from the top, consider bottom watering. This involves placing your plant pot in a tray of water and letting the plant absorb the water through the drainage holes. This keeps the top layer of soil dry, which helps to prevent gnats from laying eggs.

Now that we’ve covered prevention, let’s take a closer look at whether these pests can actually cause damage to your plants.

Can Fungus Gnats Cause Damage?

While fungus gnats themselves aren’t dangerous to humans, they can certainly cause damage to your plants—especially if the infestation is severe. The good news is that adult fungus gnats don’t cause any direct harm to plants. However, their larvae can be a different story. Let’s explore the potential damage caused by fungus gnats:

Root Damage: The main issue with fungus gnats is that their larvae feed on the organic matter in the soil, including plant roots. In young plants, seedlings, or plants that are already stressed, this feeding can weaken the plant and cause stunted growth or even death. The larvae can chew on the fine roots, limiting the plant’s ability to absorb nutrients and water.
Fungal Diseases: Fungus gnats are also known to spread fungal diseases among plants. The wounds left by larvae feeding on roots can allow fungal pathogens to enter the plant, further stressing or killing it. This can be especially dangerous in humid environments where fungus thrives.
Plant Stress: Even if your plant doesn’t show immediate signs of damage, a heavy fungus gnat infestation can stress your plants. Plants may appear wilted, yellow, or show signs of nutrient deficiencies as their root systems struggle to keep up with the damage caused by larvae.
Seedlings and New Growth at Risk: Fungus gnat larvae pose the greatest risk to seedlings and new plant growth. Because these young plants have small, tender root systems, they’re much more vulnerable to the feeding larvae. In extreme cases, a heavy infestation can kill seedlings outright.

With these methods, you should be well-equipped to eliminate fungus gnats and restore peace to your plants and home. The key is to address the problem from all angles: drying out the soil, removing larvae, and capturing adults to stop the life cycle. By combining different approaches like neem oil, sticky traps, and proper watering habits, you can say goodbye to fungus gnats for good. Happy planting!