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Did you know that there is a tiny little creature that can make your gardening experience a nightmare? No, we are not talking about spiders or snakes. We're talking about fungus gnats. These small, dark insects are biological pests that can invade your garden and wreak havoc on your plants. They feed off of the decaying organic matter at the bottom of your potting soil. They tend to swarm around your indoor plants and can be a real nuisance. But don't worry, there are ways to get rid of them. In this blog post How To Get Rid of Fungus Gnats, we'll discuss some of the best tips and tricks that will help you say goodbye to those black flies for good!

Based on our years of growing experience, we will cover in this article:

  • How to identify fungus gnats
  • What causes fungus gnats
  • Effects of fungus gnats on plants
  • How to prevent fungus gnat infestations
  • Ways to get rid of fungus gnats and
  • Top tips for keeping fungus gnats away from your home and garden in the future


Let's dive in!

What Are Fungus Gnats and What Do They Look Like?

Fungus gnats, also known as sciaridae, are very small flies. They have a narrow, long, and black body and large wings. They are generally found in moist soil where mushrooms or decaying matter is present. These tiny pests lay their eggs in the soil, feed on fungus, and destroy the roots of plants. The eggs hatch immediately into immature insects that feed and develop into fungus gnat larvae before they become pupae and, finally, adult flies. 

The whole process of the lifecycle can roughly take up to 55 days, with adult flies living only for around 10 days. They tend to be smaller than fruit flies in size at around one-quarter of an inch long. Fungus gnats can cause damage to many plants, including African violets, azaleas, banana trees, papaya trees, orchids, roses, and Schefflera. Fungus gnats can carry over 100 different pathogens, like E-Coli, which is transmitted through the feces of insects. Those pathogens can lead to infections in both humans and plants.

How Long Do Fungus Gnats Live? 

The life cycle of a fungus gnat is roughly one month long in warm conditions and just over 3 weeks in cooler conditions. There are four different stages: egg, larva, pupa, and adult.

Fungus Gnat Eggs

After mating, the female lays her eggs on moist soil in potted plants or around the edges of indoor fountains or fish tanks where there is still water present (the larvae prefer moist soil).

Fungus Gnat Larvae

After about three days, the eggs hatch into larvae that are approximately 1/8 inch long. They are legless with tapered ends and are worm-like in appearance. The larva develops through four distinct stages called in-stars before entering the pupal stage.

Fungus Gnat Pupa

Late in the fourth larval in-star, the larvae will spin a loose cocoon of silk around itself where it will darken in color while developing inside its casing for two to five days. Once the adult is fully formed, it will leave behind its old skin, which looks like an empty exoskeleton. Adult fungus gnats can live 4-6 weeks on average after emerging from their pupae cases.


The adult fungus gnat is small (about 1/10 inch long) and has long slender legs. The adults are weak flyers that resemble tiny mosquitoes.

Can Fungus Gnats Bite? 

No, unlike mosquitoes that feed on human blood, adult fungus gnats do not have mouthparts, so they cannot bite or eat solid foods, so they feed only on liquids such as plant nectar. Females can use their piercing mouthparts to lay eggs in plants and leave holes in the leaves of young plants! But don't worry, even the female ones are harmless to humans and pets.


What Causes Fungus Gnats to Form? 

A major reason why fungus gnats are found inside homes is that they have been attracted by the humidity of the house. They are most likely present in dark, damp areas such as basements and cellars, especially if they contain items such as wood. They are also attracted to moist vegetation and fresh cuttings. The larvae live in the soil or feed on fungi, which makes them most likely to be found where there is decomposition, such as compost piles with lots of decaying organic matter.

As we have already discussed, fungus gnats thrive in warm climates where the growing season is long enough for plant material to break down into organic matter that can serve as food for fungus gnat larvae. Because of their short life cycle - about 10 days at 70°F - fungus gnats reproduce quickly. This rapid growth rate makes it difficult to control large populations once they become established.

Since fungus gnat infestations are normally first detected by adults gnats flying around houseplants, many people choose to control them by spraying insecticides on houseplants. However, controlling adult fungus gnats will do nothing to get rid of the gnats already in the home. So you have to end them from the source. And, some insecticides may not be safe around small children, so they should only be applied according to label directions or an exterminator's advice.

If you are looking for a safe alternative, you can always use Flower Shield from Humboldts Secret Supplies, as they are 100% safe for both your kids and plants.

Effect of Fungus Gnats on Young Plants

Fungus gnats pose a serious threat to seedlings and young plants because their larvae feed voraciously on tender root hairs while disrupting nutrient uptake needed for healthy growth. This leads to slow growth, yellowing leaves, low yields, and eventually plant death. The damage that they cause is not immediately visible but can have a significant impact on your crop yield if they are left untreated.

Effect of Fungus Gnats on Houseplants

Indoor plants that are grown in soil or placed near standing water (such as fountains, fish tanks, or indoor potted plants) can easily become infected with fungus gnats due to the moisture content of the growing medium. This is especially true for houseplants grown in hydroponic setups like aeroponics, where there is no soil at all!


How Can You Prevent Fungus Gnats From Breeding and Multiplying in Your Environment?

Fungus gnats are attracted to water, so they often congregate around container plants. To reduce the number of these tiny flies in your home or garden, you have to eliminate them from their breeding grounds. You must completely drain standing water from planters and don't overwater indoor plants or seedlings. Also, make sure that any drains located in the soil of your potted plants have holes big enough for air to enter and prevent standing water from forming at the bottom of the plant. If you're growing herbs indoors during the winter, place them on a tray with pebbles instead of soil, so excess moisture doesn't settle at the bottom of the pot.

Check your plants for aphids or mites - these bugs attract fungus gnats because they secrete a sticky substance that gets stuck in their legs and around their mouthparts while feeding on plant juices. If your plants have either of these pests, then spraying with neem oil could help kill off any adults hanging out there! 

It's also important to stop watering your plants straight from the tap; this will encourage breeding instead if it hasn't already started happening. You should use bottled water when watering for about two weeks until all larvae have died off naturally.

Ways To Get Rid of Fungus Gnats

There are many different ways to get rid of fungus gnats, some more complex than others. Below is a list of the most common methods used by most gardeners. Some may require a larger investment than others, but all should help you control these annoying insects no matter what stage they are in their life cycle.

Remove Standing Water

Fungus gnat larvae live and breed in soggy soil that has collected too much water. By adding sand or gravel to the soil mix, you will help prevent this from occurring. You can add additives like Sweet and Sticky to your garden, so your plants don't get affected by the accumulation of sand or gravel. Sweet and Sticky is a source of carbohydrates, energy, and microbe food, needed for healthy growth in plants.

Using Yellow Sticky Traps

Yellow sticky traps are an inexpensive way to monitor the presence of fungus gnats indoors. Fungus gnats are attracted to white surfaces, so using yellow sticky traps in your potting area may tempt them in but not let them out. Place them on windowsills or near potted plants where you have noticed gnat activity. After you have caught a few adults on the sticky paper, you should see a significant decrease in the number of fungus gnats over time. These types of traps can be purchased in most local garden centers, hardware stores, or online.

Add Beneficial Nematodes

There are many different species of nematodes that prey on crawling insects, such as fungus gnats and other pests like ants and termites. They often only attack the larval stage of their life cycle, so they pose no threat to humans and other animals. These nematodes should be applied directly into the soil where the fungus gnat larvae live. They will kill the larvae and then die on their own. 

These beneficial nematodes can be purchased at most local garden centers, online, or from mail-order catalogs.  These stores provide a vial of 300 million nematodes plus an application syringe to facilitate dispersal throughout your container.

Make sure to cover all areas of exposed soil in your grow room with the nematodes directly applied to them because they need direct contact with the pupae to work effectively! Replace this layer of nematodes every 2 weeks as needed to maintain a fungus gnat-free environment.

Add a Layer of Sand to the Topsoil

This is an inexpensive way that can prevent fungus gnats from breeding in your potting soil. A thin layer of sand applied over the top before watering will allow water to pass through but will not create a growing environment for fungus gnats. This method may cause problems if you do not water correctly, so you have to be cautious!

Use a FIFRA 25(b) Pesticide

The use of a FIFRA 25(b) pesticide from Humboldts Secret Supplies like their Flower Shield can help control fungus gnat infestations indoors and outdoors. This solution is made from ingredients exempt from EPA registration, so it will not pose any threat to humans but will definitely help you get rid of pests. However, it is recommended to always read the label carefully before applying as some pesticides require specific application techniques for best results.

How to apply Flower Shield by Humboldts Secret Supplies?

As we have already discussed that flower shield is an efficient way to get rid of flies, you will be pleased to know that it is also a very effective method to kill mites and their eggs and other soft-bodied insects that infest with the growth of your plants while also controlling powdery mildew. Apply this mixture 1-3 times weekly to create a barrier between your plants and pests. The best thing is that, unlike other fungicides or pesticides, Flower Shield has no immunity build-up, which means fungus gnats – small or adults won't develop immunity against it. Follow these steps to apply it correctly:

  • Shake the bottle 1-2 times to thoroughly mix the ingredients.
  • Now measure out the 2oz of liquid and dilute it with a gallon of water for the initial application. You can tone it down to 0.5/per gallon after 2-3 weeks. 
  • Put this diluted the Flower Shield mixture into any spray bottle and shake it well for a couple of minutes before applying it to your plants. 
  • Apply it to the plant's foliage to prevent the growth of fungus gnats and other pests that creep into the plant and disrupt healthy growth. (Never apply it directly to the roots of plants)
  • Don't forget to wear gloves before application.
  • Always apply the flower shield early in the morning or in the evening, or when your main grow lights are off and allow adequate drying time before the sun comes out or main lights are back on.


Prevent a Fungus Gnat Infestation

Fungus gnats can be troublesome in the late summer and early fall when your plants are most vulnerable to infestation. Taking proactive steps such as applying a layer of sand on top of your soil before watering will help prevent an outbreak before it occurs! But it doesn't mean that your plants have to suffer because of that. You can use additives like Plant Enzymes to rejuvenate the soil and add Calmag & Iron to help with common plant deficiencies like calcium, magnesium, and iron. 

Other Treatments 

Insecticidal soaps and oils are also effective for eliminating fungus gnats, but you have to apply them directly to your plant leaves, not just on top of your growing medium. Both natural chemical surfactants like insecticidal soap and horticultural grade oil formulations like Neem Oil provide an effective means of controlling fungus gnats on plants without damaging their buds or roots! But you have to completely soak the top three inches of the plant with neem oil for this method to work efficiently.

Insecticidal Soap or Oil?

Both soaps and oils can be effective at controlling fungus gnats, but what you use depends on the situation. Insecticidal oils are more useful for soilless growing mediums like coco coir because they spread out evenly over all exposed areas of the growing medium, effectively depriving fungus gnat larvae of an adequate supply of nutrients to survive! Oil also acts as a non-selective pesticide that will kill any insects that come into contact with its residue after 2-3 days. This is a great method for preventing fungus gnats from reestablishing their populations in your greenroom! 

On the other hand, insecticidal soap is most useful when applied directly to your plant's leaves as it will kill fungus gnats that come into contact with its contents! Soap is best used to treat infestations as they occur because, unlike oil, soap doesn't leave a residual pesticide and won't repel fungus gnats away from your plant if applied at an adult stage.

There are several organic and chemical pesticides registered for use with the EPA, including pyrethrins, and BT (bacillus thuringiensis), that can be effective at controlling fungus gnat populations. However, if you choose to use any type of pesticide, we recommend treating your grow room as a full-cycle indoor grow area. This means you should never begin growing in this same space ever again since harboring even a low fungus gnat population can potentially cause devastating problems with your future yield!

Top Tips For Keeping Fungus Gnats Away from Your Home and Garden in The Future

Fungus Gnats can be quite difficult to control once populations reach adulthood, but there are several steps you can take before they ever become an issue. Here are some steps that you should follow to keep fungus gnats away from your garden.

  • Always keep indoor plants on trays of sand or gravel and never water directly from above. Instead, start by pouring your nutrient solution over your plant through a drip irrigation system or a sprinkler sled for even distribution. This will eliminate the chances of standing water and ultimately reduce the formation of fungus gnats.
  • Fungus gnats also enjoy light, and they congregate around windows and doors whenever they're available. To prevent further infestations, seal up any cracks or holes that could allow light in your home.
  • A mixture of one part apple cider vinegar and one part water can be sprayed on the soil surrounding your houseplants to prevent a fungus gnat infestation. The vinegar will kill fungus gnats and any larvae before they can grow into adult flies and lay eggs.
  • Avoid wetting the top of your soil or growing medium during watering and always keep indoor plants on trays filled with moist peat moss.
  • Fungus gnats also need a moist environment in order to live. If possible, try to reduce the humidity levels in your home or yard.
  • Gnats usually attack the drainage holes of plants and start laying eggs at the bottom of these pots. It's best to cover the holes with some synthetic fabric and tape or rubber bands. This will not only seal in the moisture and act as a barrier for gnats' growth but also kill off any larval activity in the soil.
  • Use a mixture of mosquito dunk to prevent the fungus gnat's growth. You can mix mosquito dunk with one gallon of water and let it sit all night. In the morning, water the plants using this mixture, and you won't have to deal with fungus gnats ever!

Tip: Those who want to avoid the hassle of going through the ingredients and preparing different mixtures can always use Flower Shield to protect their house plants. This is not only an effective method to knock down the pest but can also save tons of effort and time, allowing you to enjoy your freshly grown fruits and veggies to the fullest. 


It can be difficult to find the source of fungus gnats. But there are some easy ways you can get rid of these pests for good, starting with checking your plants' soil and drainage systems for any debris, build-up, or moisture that might attract the insects. You should also use Flower Shield from Humboldts Secret Supplies on all flower pots or hanging baskets to ward off pesky gnats while they drink nectar. 

This solution creates an invisible barrier around your plants that prevents fungus gnat larvae from getting into them while they grow. Plus, this product is fragrance-free, so it won't interfere with what's already blooming! You may also want to consider using this product if you have problems with other types of pest infestation on your property or even for indoor use as giving up is not always necessary when it comes to solving garden woes! 

We hope this article has helped you learn how to get rid of fungus gnats, let us know if you've tried any of these techniques in the comments below!

1 comment

  • Having a huge problem with fungus ghats what do I’m growing my plants organic soil don’t want to harm the plants or the soil

    Gord Elias

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