How Do I Get Rid of Gnats in My Potted Plants?

Last Updated on March 14, 2022 by Grow with Bovees

Having gone to the trouble of investing time or money, or both(!) in a beautiful houseplant(s) to complement your home, the last thing you want is pesky bugs spoiling their appearance.

If you’ve started noticing tiny, fly-like flying insects around your home, particularly around your houseplants, then you’ve very likely got a fungus gnat infestation!

However, when it comes to getting rid of fungas gnats, there’s good news and bad news.

The bad news is that both fungus gnats and their larvae can absolutely destroy your houseplants quickly if you’re not vigilant, and allow them to spread like wildfire.

The good news is that fungus gnats in houseplants cause less damage than a lot of other pests, and you can get rid of your fungus gnat problem by following the following tips.

Fungus Gnats or Fruit Flies?

Even though fungus gnats and fruit flies are considerably similar in terms of looks, there are a few distinct differences that set the two apart.

Identifying the two will make it easy for you to employ the right solutions to get rid of the appropriate pests.

Fungus gnats are black in color with black eyes, whereas fruit flies have bright red eyes and a brownish head and thorax.

While both insects have small bodies that measure between 1/16th to 1/8th inch in length, fungus gnats have disproportionately large, gangly legs that are similar to those of tiny mosquitoes, which is one of the reasons they are able to jump and fly away quickly.

Fruit flies mostly hover around fruits, and fungus gnats around houseplants and potting soil.

In fact, the excess moisture in potting soil provides the perfect conditions for fungus gnat larvae and adult gnats to thrive on the roots and organic matter of your houseplants, a favorite treat for them that helps them grow and survive.

If you have unused potting soil hanging around, be sure to properly store left over potting soil, as it will attract gnats.

Contrarily, the flies thrive on ripe fruits and vegetables lying around on your kitchen counter, and in your garbage bins.

These flies can be harmful to humans due to certain bacteria they carry, which is why it’s important that you wash your fruits and veggies before consumption.

Some species of fungus gnats can bite humans, resulting in tiny red bumps that can be itchy and irritating, yet another reason to get rid of them.

What Types of Fungus Gnats Affect Houseplants?

Fungus gnats are a broader term that includes six different families of insects — Sciaridae, Mycetophilidae, Ditomyiidae, Bolitophilidae, and Keroplatidae.

Out of these six families, there are just two — Mycetophilidae and Sciaridae that are regarded as pest gnats in houseplants.

While the adult gnats don’t usually cause long-term damage, it’s the larvae that you have to watch out for and get rid of.

The life cycle of these houseplant pests is made up of four stages, namely eggs, larvae, pupae, and adult gnats.

They tend to have a short lifespan, about a week or so as adults, but they can do a lot of damage during this time.

Female gnats lay eggs in rich, fertile, and moist soil or potting mix located at the base of your houseplants. The larvae emerge approximately four to six days after the eggs are laid.

You may not notice the gnats in houseplants in their larvae stage because they are extremely tiny, but they increase in size rapidly as the larvae feed on the organic matter in the soil.

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The pupal stage starts after the larvae have reached their maximum growth, and lasts for three to four days.

Owing to this quick and rapid growth life cycle, fungus gnats in houseplants can be present in many stages at the same time, so you have to get rid of fungus gnats in larvae and adult stages.

Where do Fungus Gnats Come From?

Fungus gnats can start taking up residence in your house in several ways. But the most common way these pests get into your house is through newly purchased bagged compost or soil, and /or potting mix that you bring indoors.

Apart from potting mix and soil, they can even enter your home through houseplants that were previously outdoors during the summer and can fly in through an open window or door.

Preferred Habitats for Fungal Gnats

While there are several areas of your home that can serve as a breeding ground, the fungal gnat larvae and adult flies love moist and rich soil that is generally a bit over-damp.

Adding to this, soil mixes that are rich in peat moss or coconut coir can also encourage female gnats to lay their eggs and breed.

A gnat problem is not limited to the summer months but is also evident in warmer areas of your home and garden, such as greenhouses during the winter.

Greenhouses are actually a much better breeding facility for gnats because the plants in there do tend to contain rich soils, and have been watered regularly.

Fungus gnats love to munch on the roots of your house plants, but will also feast on your plants themselves when there’s a lack of organic root material in your house plants.

Furthermore, there are certain plants that are more susceptible to fungi gnat infestation than others such as geraniums, poinsettias, carnations, and African violets.

Some exotic plants like Philodendrons, Peperomias and Caletheas have also been known to attract these pests.

As mentioned earlier, fungal gnats can appear in both the summer and winter months but tend to strike during the fall.

Will Fungus Gnats Kill Plants?

The short answer is no – fungal gnats will not kill your houseplants but they are definitely a nuisance!

However, a heavy fungus gnat infestation can cause extensive root damage which will certainly negatively affect the health and therefore appearance of your plant.

On a brighter note, these pests will only eat rotting roots.

One of the biggest reasons to get rid of fungus gnats is because of their ability to fly which means they can quickly spread themselves all over your house and that is really annoying.

How to Kill Fungus Gnats?

There are many different ways to get rid of gnats, but it may be a bit difficult if you have a multitude of indoor plants.

Just like plant flies, adult gnats only live for a few days, but in that time, they can fly from plant to plant, laying a LOT of eggs wherever moist soil is present.

1. Control soil moisture

Since moist soil is the preferred breeding habitat for fungus gnats, the easiest way to control the problem is by refraining from overwatering your houseplants.

But this is a fine line to tread as you also don’t want the potting soil of your houseplants to dry out completely.

To avoid risky guesswork, you can use a soil moisture gauge to render the accurate level of soil moisture to get rid of fungus gnats easily. You can also buy an indoor watering device to water your plants easily and automatically.

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2. Water plants from the bottom

The top inch of the soil is where fungus gnat larvae tend to thrive, which also tends to be a pretty moist area, given that most people water their plants from the top.

By switching to watering your plants from the bottom, you stand a better chance of maintaining their overall health, by keeping the soil dryer at the top which is perfectly fine because the roots are below the surface anyway.

You can water your plants from the bottom by pouring water into the bottom drip tray, and allowing the plants to soak up the water through the available drainage holes.

But it’s highly important that you get rid of any excess water from the drip tray after around 30 minutes of soaking, otherwise, you risk overwatering your plants.

3. Use yellow color houseplant sticky stakes

The color yellow is a very useful tool in garden pest control, because both young and adult gnats, along with other plant pests, are naturally attracted to bright colors.

However, it’s worth mentioning that putting yellow sticky traps will only be effective at controlling the adult gnat population, and is not a permanent pest control solution to get rid of them for good.

These yellow traps will however keep the numbers of adult fungus gnats down and hopefully prevent them from flying all over your house, and onto other plants.

4. Apply organic pest control products

To get rid of a gnat problem, you should try and use organic pest control products, because remember that these insects live in your house, so applying poisonous chemical pesticides could risk unwanted areas of your home becoming contaminated and harming children and pets.

You can make your own cheap organic solution to eliminate gnats by mixing a few drops of dish soap with vinegar and baking soda in a spray bottle.

Then simply spray the mixture in areas where the gnat population is evident.

Another proven concoction for killing fungus gnats is a mixture to a ratio of; two tablespoons of apple cider vinegar, six drops of liquid dish soap and a tablespoon of sugar.

Neem oil, if you can get hold of it, is also a great way to get rid of gnats, and also helps prevent any future occurrences.

5. Mosquito dunks can help get rid of fungus gnats in houseplants

Mosquito dunks are used to keep mosquitoes and their larvae away from populating fishponds, animal troughs, and other small bodies of water.

Mosquito dunks contain a dry pellet called Bacillus Thuringiensis, which is a beneficial bacteria that infects and kills larvae of soil gnats, flies, and mosquitoes.

Using mosquito dunks is quite straightforward, when you fill up a gallon of water, toss one of the dunks into it.

For best results, you can break up the mosquito dunk into smaller pieces, before putting them into the water. Let the mosquito dunk soak in water at least overnight, after which remove it from the water, and spray or pour this water over the soil surface or plant roots where fungus gnats are present.

6. Use Steinernema Feltiae for large or uncontrollable fungus gnat problems

Steinernema feltiae, also referred to as insect parasitic nematodes have been used extensively for many years to control fungus gnats.

These microscopic non-segmented roundworms kill fungus gnats by entering into their systems, usually through their mouth or anus.

You can buy Steinernema Feltiae online or at your local garden center, and then use it to kill any gnats in houseplants, tropical plants, greenhouses, and grow rooms.

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7. Remove the fungus gnat infested soil

Since fungus gnat larvae and adults are generally found on the top layer of potting soil, removing this layer and replacing it with new soil before you even use any of the above methods, will accelerate your efforts of getting rid of fungus gnats.

However, keep in mind that the fungus gnat eggs and larvae are still present in the soil that you have removed, so make sure you dispose of it accordingly in the trash.

8. Use soil covers

Soil covers not only add a nice, decorative touch to your houseplants but also suppress the reproduction of fungus gnats.

Given that fungus gnats need moisture to survive, they will not be able to grow under the soil covering. Soil covers also contribute to the fertility of your soil and are available in a plethora of different options.

9. Cover the soil with stones

Putting rocks on top of potted plant soil will make things much more difficult for the gnats to creep in to lay their eggs. The rocks are also a nice addition to the decor.

Will Treating the Soil with Hydrogen Peroxide Kill Fungus Gnats?

You’ve probably already used hydrogen peroxide to treat cuts and burns at home, but the big question is can it be used to control gnats? And the answer is, yes it can.

Hydrogen peroxide feeds on fungi and loves moisture, two of the primary food resources for fungus gnats.

Rain actually has small traces of hydrogen peroxide that help cleanse and oxygenate your plants growing outdoors so it makes sense that it can benefit your indoor plants as well.

Diluted correctly Hydrogen peroxide is safe to use on plants and around your house and garden as it doesn’t harm pets, humans, or any of the more favorable insects such as ladybugs.

To use it to spray fungus gnats, mix one-part (3 percent) hydrogen peroxide with four parts water. Allow the top layer of your soil to dry, and then water your plants as you normally would with this solution.

Your soil may fizz for a few minutes after application, but this is normal and indicates that the hydrogen peroxide is reacting.

How To Stop Gnats Spreading To Other House Plants

Firstly, the best way to prevent fungus gnats from spreading is by quarantining your infected plants away from the other houseplants. (A course of action we are all sadly, very familiar with these days!)

Secondly, stick a couple of sticky yellow stakes in any infected plants so that if any new fungus gnats hatch, they won’t get very far.

Final Thoughts

We choose to have houseplants in our homes primarily for aesthetic purposes.

While fungus gnats aren’t going to destroy your house plants completely, they will affect the overall health and appearance of your plant.

They are also unpleasant and irritating to have flying around your house!

If you act quickly as soon as you spot them, then a cheap, homemade solution is all that you need to keep them at bay and for more serious infestations there are more serious remedies widely available.

There is definitely no need to live with fungas gnats in your home!

We hope you’ve found this article helpful.

Yours in House Plant Happiness,

Lizzy & the Bovees team