What Are Fungus Gnats? How To Get Rid Of Them Easily


Picture of a Fungus Gnat resting on a leaf

House plants are not only refreshing, but they also breathe life into your space and add a pop of color. However, having some unwelcome insect infestation around your houseplants is the last thing you would want to experience. Fungus gnats mostly appear when you water your plants, and they are particularly harmful to young plants and very annoying to humans, especially indoors.

Fungus gnats are common plant pests, usually, fruit fly-sized, and mainly affect indoor house plants. You will mostly notice these insects when the harmless adults start flying around the house plants. Although the flying adults are a nuisance, the larvae stage is harmful to plants since they feed in the soil, damaging their tender roots.

Fortunately, you can get rid of fungus gnats naturally.

  • Since the larvae are in the soil, make their natural habitat inhospitable by drying out the soil since they need it in moist conditions. Letting the soil dry out completely before watering it will help eliminate the larvae and discourage the adults from laying eggs.
  • Alternatively, you can use a mixture of soap and water with a few drops of liquid dish soap. Spraying the top of the soil using this mixture kills the larvae, but you’ll also need or repeat the process after a few days to ensure that you’ve killed all of them.
  • You can also set up traps using yellow note cards covered in a sticky adhesive. To make them more effective, cut them in small squares, attach them to skewers just above the soil, or place them on top. The cards will trap the adult fungus gnats as they crawl or fly onto the card. The yellow sticky cards attract the fungus gnats.

If you enjoy having houseplants but do not fancy having fungus gnats, this guide will significantly help as we expound further on these annoying insects and how best to get rid of them for good.

How to Identify Fungus Gnats?

Initially, I thought that my house plants had fungus gnats, only to discover that they were actually fruit flies. It is essential to know the pests that have infested your plants to employ the proper extermination methods and prevent them from attacking your plants in the future. This is how I identify fungus gnats on my houseplants:

Size

The adult fungus gnats are the first sign that most people notice in their homes. They are usually tiny, like fruit flies with sizes ranging from 1/16th to 1/8th inch long. Their larvae have a length of about 1/8 inch.

Appearance

Adult fungus gnats are either black or dark grey with see-through wings. They have long antennae and long legs that make them have a mosquito-like appearance, although they are still smaller than mosquitoes. On the other hand, the larvae have a pale or white see-through complexion with a thin body. Also, the larvae have small blackheads, usually at the tip of their body.

Activity

Typically, fungus gnats will fly in the house but will mostly stick around potted plants, which becomes their new home. Since they aren’t strong fliers, they tend to walk along with the soil and then fly into short bursts near drainage holes and on the outer edge of the pot.

Also, since they lay their eggs in the houseplant soils, they tend to stay close to these areas, although they are easily distracted by light, just like other insects. Therefore, you will also notice them flying around your light bulbs, windows, computer monitor, or your TV. I noted that their flight is much more erratic and also slow, acting like mosquitoes.

These insects are sometimes annoying as they can also fly into people’s faces and fall into your sugary and sweet drink. However, they are entirely harmless to humans.

Causes of Fungus Gnat

Although it’s a good idea to know how to get rid of fungus gnats, knowing the preventative methods ensures that you never have to encounter these annoying insects in the future. You, therefore, need to understand what causes these insects to attack house plants in the first place.

As earlier stated, you will find fungus eggs on overly moist plant soils. People with extensive outdoor gardens may have also noticed these insects in the damp rotting wood. If the decaying matter is moist with fungus growing on it, mainly on the topsoil, it will attract these insects fast. Therefore, the earlier the intervention, the better to try and eliminate fungus gnats.

Therefore, if you notice any adult fungus gnats flying around, no matter the number, act fast by implementing any preventative measures highlighted above. Note that the life cycle of fungus gnats is incredibly fast, so you will need to act quickly.

The adult fungus lives for at least one week, but they can lay up to 300 eggs within this short time. In four to six weeks, the eggs hatch, and the larvae start snacking on the roots on your house plants in the moist, rich topsoil. Within three to four days, the pupa larvae become adults, so these insects’ populations can explode quickly.

Possible Damage Caused by Fungus Gnats

When fungus gnats are in small numbers, mainly indoors, they tend to be annoying but don’t actively harm humans or plants. However, when you allow them to thrive and become a large enough colony, you’ve got a bigger problem to deal with.

Soon, the larvae will start feeding on your plants, and you will start noticing some considerable damage, especially on young plants with few delicate roots. Still, the fungus gnats can spread plant pathogens that lead to damping off and then cause the death of seedlings. The damage caused by fungus gnat appears somewhat similar to any other root-related problem like root rot.

The plants’ growth will mostly slow down significantly or even stop entirely, and the lower leaves can start turning yellowish then drop. In worse cases, the plants might start wilting and then die since the roots are heavily damaged.

How to Prevent Fungus Gnats Infestation in Your Plants?

While there are several ways to get rid of these annoying insects, you can also utilize a few tactics to prevent fungus gnats’ infestation from getting to your houseplants. Besides, you don’t want to start the process of getting rid of the insects once again. Here are ways that you can implement to prevent fungus gnats infestation with nearly zero effort:

The video below will show multiple ways of dealing with many garden pests including fungus gnats.

Thoroughly Inspect Houseplants Before Purchase

Suppose you notice a fungus gnat flying from the potted plants while at the garden store, reject it immediately and the other plants around it. An essential technique that I learned while purchasing house plants is to turn up about an inch or so of the soil in the potted plants to see if you can spot any larvae.

Keep the Extra Potting Soil in an Airtight Bag

In most cases, people keep the excess potting soil in the packaging bags they come in. However, there is a high possibility of fungus gnats getting in these bags and laying eggs. Therefore, you can opt for airtight containers such as a bucket with tight-fitting lids to keep fungus gnats at bay.

Watch Your Watering

These insects like moist areas, so you should ensure that your containers have good drainage. Also, only water the plants when the top one or two-inch soil gets dry, especially during the winter when plant growth tends to slow down. Maintaining dry topsoil discourages these insects from laying eggs.

If necessary, add perlite to the potting mix to improve drainage for those who tend to overwater their plants. Still, you can water the plants from the bottom, so the topsoil remains dry while still keeping the plants hydrated and happy. You also need to empty all the excess water on the saucers under the container plants.

Make Sure You Cover the Drainage Holes

While you may pay more attention to the topsoil portions, fungus gnats will seek out the drainage holes because of the moist conditions that encourage them to lay eggs. Therefore, you will need to cover them too. Look for a synthetic fabric to cover the drainage holes to ensure water still passes through and won’t rot.

You can use rubber bands, tape, or glue to keep the fabric in place. Keeping the bacteria in the soil will stop these annoying insects from going through their normal life cycle in your houseplants. As a result, there won’t be any adults flying around or young larvae harming the roots of the small plants.

Minimize Debris

Decaying organic matter is the perfect place for the fungus gnats to lay their eggs. Therefore, it’s essential to keep any plant debris away from the soil around the house plants. This can include flowers, fruit, fallen leaves, and other debris. If these insects are ever-present around your houseplants, you can opt for a potting mix that doesn’t come with ingredients such as bark fines, actual compost, and processed forest products.

Use gravel or sand

Another clever method that I learned was replacing the top inch of the soil in your house plants with gravel or sand. Since fungus gnats will only lay their eggs on the topsoil, gravel or sand takes away the rich nutrients they usually munch on. With their food source taken away, the insects won’t lay eggs on your plant’s soil.

Introduce the Fungus Gnat Predator

Some of the aforementioned preventative methods may not be fully effective for the fungus gnats for those with a large-scale garden. In this case, you can incorporate a predator into the mix while also utilizing other measures.

The Stratiolaelaps scimitars is a good predator as it seeks out these frustrating fungus gnats’ larvae and other insects that may be in your garden. You can order these mites from several stores, and they come in bottles that can contain up to 25,000 of them. With the many mites that you can receive, it’s not advisable to try this method on plants within your home.

Conclusion on how to get rid of fungus gnats easily

To completely eradicate fungus gnats, stop the eggs from hatching to stop the larvae from developing. Failure to proactively fight these insects in their early stage means that you’ll keep dealing with the adults every time.

Besides, the leading cause of fungus gnats infestation, whether indoors or outdoors, is primarily due to a lack of people playing their part. You must attack these insects in at least two early stages of their life cycle to ensure that you get rid of the replication.

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Tony O'Neill

I am Tony O'Neill, A full-time firefighter, and professional gardener. I have spent most of my life gardening. From the age of 7 until the present day at 46. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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