How to Deal With Fungus Gnats on Your Houseplants

We never want to see our plants suffer at the hands of pests, and we especially don’t want to see bugs in our houseplants since that brings the issue inside our homes—ugh! 

Fungus gnats are tiny, winged insects that resemble tiny mosquitoes and are roughly the same size as fruit flies. The good news is that these plant flies are less harmful to your house plants in comparison to other pests, and they’re also simple to get rid of.

When gnat infestations get out of hand, their larvae can cause significant plant damage that may even kill young seedlings. 

They feed directly off the roots, which is what makes them hard to spot at first because adults lay tiny black eggs near root hairs along with other fungi spores that help the fungus grow faster, causing further issues for stressed plants.

In this article, you will learn how to identify fungus gnats and what treatment methods work best for getting rid of fungus gnats on your houseplants.

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Table of Contents

What are Fungus Gnats?

Fungus gnats are tiny, black flies that resemble mosquitoes. They have long legs and one set of wings, while fungus gnat larvae look more like maggots—small white worms with brown heads that feed on the roots of houseplants.

The fungus gnat’s eggs are laid near root hairs in moist soil conditions because fungus gnats thrive when their food is wet or decaying. Adults live for roughly two weeks after mating, but females lay 100-300 eggs during this short time frame before dying off themselves. The life cycle from egg to adult can range from 25 days up until 40 days depending on what factors surround it (temperature, humidity levels).

fungus gnat on leaf

Signs that you have fungus gnats include

Identifying a fungus gnat infestation is simple. These plant fliers aren’t too good at flying, so they’re generally near to the plant. You’ll undoubtedly see them zigzagging about. Because they reproduce so quickly, you may often observe all of the pest’s phases at once. If you stir the dirt gently, you’re likely to come across some remaining larvae. They have translucent bodies and black, reflective heads, and eat organic matter in the soil.

With winter arriving here in the UK, most gardeners are now bringing their plants in to settle down for the cold season. Unfortunately, this means that the insect populations that are causing you problems now will soon peak. Dormant house plants require less water during the winter period, so their soils are wet for longer. Gnats thrive in moist ground, which encourages root rot and fungus growth. Bring your sensitive plants inside to overwinter with caution, since you might be bringing home pests that you don’t want into your house.

If left unnoticed and untreated, your house plants will begin to show signs of stress. While fungus gnats don’t damage plant leaves directly, they munch on root hairs and diminish the soil of essential nutrients. This can lead to the sudden wilting and yellowing of plant leaves, weak growth, and an overall loss of vigor.

How can you get rid of greenfly on roses? Have a read of a blog that we wrote that covers this.

red and green house plants attract fungus gnats

How do Fungus Gnats Harm Plants?

Adult fungus gnats don’t cause much harm to plants since they feed on fungus spores and decaying matter in the soil—but fungus gnat larvae can be harmful when there’s a large infestation. They’re attracted to root hairs of almost any houseplant because it’s easy to access for them to eat away at nutrients that plants need.

The fungus gnat pupae is also an issue since these immature flies stay near the surface of the soil until they become adults; this behaviour makes it even easier for fungus gnat populations to spread throughout your home if they aren’t dealt with promptly.

The fungus gnats themselves don’t usually cause significant damage to houseplants, but the fungus that they carry does—and this fungus can also be passed on from plant to plant if you have multiple houseplants in your home or office. If left untreated, fungus gnat infestations will quickly take over a greenhouse and eventually kill off all of your plants within six months.

moist soil

What are Fungus Gnat Treatments?

Fungus gnats thrive when their food is wet or decaying, so make sure you avoid overwatering any indoor house plants during winter to prevent an outbreak from happening at all. One way to control fungus gnats as well as other pests indoors is by regularly cleaning up fallen leaves, fungus, and other decaying organic matter from the bottoms of houseplants.

If you do find fungus gnats on your plants or in a greenhouse, it’s important that you take action quickly to get rid of fungus gnat populations before they grow out of control—because getting rid of fungus gnats can be difficult once their population is large enough to spread throughout an entire room.

You’ll need insecticidal sprays labelled for indoor use against fungus gnats. If there are only a few adult flies present, these sprays may not kill them immediately but will decrease future reproduction rates if applied consistently over time.

decaying plant material

Natural Ways to Get Rid of Gnats

When it comes to fungus gnat control, the first step should always be natural control methods. While chemicals are sometimes required as a backup, natural and organic treatments are typically the least harmful and disruptive to your plant and home. If they’re detected early enough, most fungal gnat populations can usually be prevented and eliminated naturally. Keep in mind that one plant container can house up to four generations of bugs, so multiple applications of your chosen technique are likely required. Here’s how to get rid of gnats in your houseplants:

Avoid Overwatering

As mentioned above, overwatering your houseplants can significantly increase your chances of developing a fungus gnat infestation. Before watering your houseplants, allow the top few inches of soil to dry out. Not only will this prevent fungus gnats from selecting your plant as their new home, but it will also hinder their reproductive cycle and assist reduce populations that have already arrived.

overwatering houseplants

Sticky Tape

One fungus gnat treatment that can be used indoors is putting down strips of double-sided sticky tape around the base of your houseplants. The fungus gnats will get stuck on it, preventing them from getting to your plants and laying eggs there. This method won’t kill fungus instantly, but instead, prevent future generations from hatching or growing in size. This could be a good natural fungus control option for you.

yellow sticky traps

Cider Vinegar Traps

Place equal quantities of cider and vinegar in a shallow dish or can, similar to how you might catch fruit flies. Place the trap near the afflicted plant or even on the soil surface within the container. The pests will be drawn to the mixture, but once they fall into it, they will drown.

Want to know how you can make your own natural vinegar spray for aphids? Have a read of this article we wrote that covers this. 

vinegar kills fungus gnats

Nematodes

Controlling pest numbers may sound like a bad idea, but it’s actually quite simple. Nematodes are teeny-tiny wormlike creatures that are typically so tiny that they can’t be seen with the naked eye. They attack fungus gnats and other insects in their larval state, releasing bacteria that consume the pest from the inside out. It’s unpleasant to consider, but not as awful as allowing gnats to kill your beloved plants!

Dealing with Fungus Gnats Using Insecticides

If you don’t have any luck using organic methods, insecticidal sprays and preparations are always available to combat insect infestations. There are several treatments that target the larval stage or adult stage, but either is acceptable. You should be able to eliminate these horrible plant flies in a few weeks if you successfully target one phase of their lifecycle and reapply on a regular basis.

fungus gnat eggs

Neem Oil Spray

Another fungicidal spray that’s safe enough to use on indoor plants is neem oil. Neem oil should only be applied directly to soil as an added preventive measure against fungus gnats since it can damage plant leaves when diluted incorrectly—and never apply neem oil near water sources like ponds or streams.

Hydrogen Peroxide

Hydrogen peroxide is an excellent method to destroy larvae on contact, eliminating them instantly. Soak your soil in a solution consisting of four parts water and one part hydrogen peroxide. The fungus gnats will be killed upon contact with the water, and any fungus gnat larvae that come in contact after this initial treatment may also die.

Although fungus gnats aren’t known to cause illness in humans, their presence in your home may have a negative influence on your houseplants. Your plants will repay you by providing a lovely, healthy appearance to brighten up your space with these pests eliminated.

larvae feed

Other related questions

Does Cinnamon help with fungus gnats?

Chamomile and cinnamon are effective natural fungicides that destroy the gnats’ major food source, making the soil uninviting.

Are gnats attracted to coffee grounds?

Although fungus gnats don’t enjoy coffee grounds for food, the fungus in the soil might. Coffee is an effective fungus control method to get rid of fungus and fungus gnat infestations.

Are gnats attracted to poop?

Fungus gnats and fruit flies are the most common offenders. Both like moist locations, such as a litter box or a scooping container. The type of litter you choose may also be an attraction.

cat litter

Do fungus gnat bites itch?

No, fungus gnats do not bite humans or pets at all. They’re just an unsightly pest that feeds on fungi found within plant pots and home environments. This feeding causes the adults to lay eggs inside moist dirt, where young maggots will eventually hatch into adult fungus gnats before dying shortly thereafter without causing any harm to anyone other than our houseplants!

What is the difference between fungus gnats and fruit flies?

The colour of fruit flies varies from tan to black. Fungus gnats are dark grey or black in colour. Fruit fly bodies are rounded, similar to a smaller version of the common housefly. Fungus gnat bodies, on the other hand, have dangling legs and lengthy torsos that make them appear like tiny mosquitoes.

fruit fly

What smell do gnats hate?

Both fruit flies and fungus gnats, also known as “gnats,” are guided by their excellent sense of smell. You may utilize repellents that they despise, such as peppermint, lemon, eucalyptus, vanilla, lavender, citronella, and deet to deter gnats.

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