Fungus Gnats: Identification and How to get Rid of Them?

Al Ardh Alkhadra > Blog > Gardening > Fungus Gnats: Identification and How to get Rid of Them?

fungus gnats

Fungus Gnats belongs to the families Mycetophilidae and Sciaridae.

These are common pests of plants that you grow indoors, especially when the humidity and moisture are high.

There are often first notices when you notice the harmless adults flying around your house plants or gathering them at nearby windows.

These non-biting adult gnats can also become a flying nuisance.

However, it’s the larval stage, feeding in the soil that can damage the tender plant roots.

Moreover, fungus gnats can quickly become an issue in your home if an infestation gets out of your hands.

However, with the help of consistent management and prevention techniques, you can make sure there is no recurrence of infestation in your house plants.

Keep on reading to learn more about fungus gnats.

Fungus Gnats

Fungus gnats are fruit-fly-sized insect pests that usually affect indoor houseplants.

These pests are attracted to the moisture of potting soil while the adult gnats lay their eggs up to about 200 on organic matter near the soil surface.

After about 3 days, the eggs hatch into larva, which then burrow into the soil to feed on fungi and decaying plant material.

Two weeks after, adults gnats emerge from the soil to repeat the process and they live for about one week.

It is important to note that fungus gnats are completely harmless to humans as they are unable to bite and do not spread diseases.

fungus gnats 2

However, they can be a problem for your houseplants when their population increases and their larvae start to feed on the thin roots of the plants.

Moreover, fungus gnats may also spread Pythium.

It is a group of plant pathogens that causes ‘damping off’ in seedlings.

Once you have fungus gnat infection in your home, using consistent management and prevention is the key to ending them.

Identifying Fungus Gnats

To identify fungus gnats, consider the following:


Adult fungus gnats are tiny and their size ranges from about 1/16 to 1/8 of an inch in length or 1.5 to 3mm.

This is about the same size as that of a fruit fly. Moreover, their larvae may be up to 1/8 of an inch in length.


Adult fungus gnats are greyish-black and have gray or see-through wings.

fungus gnats 1

Moreover, their long legs and long antennae give them a mosquito-like appearance, though they are much smaller in size.

In comparison to a fruit fly, fungus gnats have a thinner body with long legs and antennae, while larvae have a small, black head, and a thin or see-through body.


It is important to note that fungus gnats tend to spend most of their time on the surface of the soil of potted plants.

However, you can also see them flying around the outer edge of the pot or near drainage holes as well.

They are not strong fliers, so they have a tendency to walk along the soil and fly only n short bursts.

Furthermore, their flight is erratic and they tend to be much slower than fruit flies, acting more like mosquitoes while flying.

Annoyingly, they also have a tendency to fly into the face and drink the people.

Though they are completely harmless and few-placed swats will show them what’s what.

Damage Fungus Gnats Causes

In small numbers, fungus gnats are more of an annoyance than anything.

In fact, the adult gnats will not actively harm the plants or people.

However, if the population gets out of the hands, the larvae can start feeding on plant roots, causing notable damage.

Moreover, this is particularly bad for young plants, like seedlings, which only have a few delicate roots.

damage to the plants

Fungus gnats are also capable of spreading the plant pathogen that causes damping off and the eventual death of seedlings.

Furthermore, fungus gnats damage tends to appear just like that of any root-related issues like root rot.

Lower leaves may turn yellow and drop, and the growth of the plant may slow down or stop completely.

In particularly bad cases, wilting of the entire plant can take place following the death of the pant if there is extreme damage to the root.

Controlling Fungus Gnats

Getting rid of fungus gnats is all about consistency while catching the adults in gnat traps is fairly easy.

However, as the adult population comes in the cycle, you will need to make sure that the traps are refreshed regularly.

For the best results, use a combination of the following items as well as additional preventive methods in the subsequent section:

Stick Card Traps

These traps consist of yellow note carb that is covered in a sticky adhesive.

Moreover, they are most effective when you cut them into small squares and place them directly on the top of the soil.

Or when you attach them to the skewers just above the soil.

Adults gnats will fly or crawl onto the card and will be trapped in the glue.

It is important to note that fungus gnats are attracted to the color yellow, so make sure to use yellow sticky cards rather than blue ones.

You can buy both at most hardware or garden stores, as well as online.


Cider-Vinegar Traps.

These are simple and effective, cider-vinegar traps.

It consists of a shallow container with a small amount of apple cider vinegar, water, and liquid dish soap.

To make a cider vinegar trap, follow the steps below:

  • find a shallow container, eg, a tuna can be perfect for this
  • fill it with equal parts water and apple cider vinegar, and make sure that the liquid should be at least 1/4 inch deep
  • put a few drops of liquid dish soap into the mixture and stir gently
  • place the trap near the base of the affected plant
  • or you do place it inside the pot on top of the soil
  • make sure to check it every few days to refresh new vinegar and water


Flypaper ribbons like those you bang in horse barns to catch outdoor flies can also be used to catch fungus gnats.

However, these traps often overkill the gnats and can easily get stuck to things you do not want them sticking to.

These can include furniture, hair, plants, and so on.

Preventing Fungus Gnats

You can use the following prevention techniques in tandem with the traps mentioned above for the best results:

Keep the Soil Dry

It is important to note that fungus gnats seek out moist soil.

Therefore, allowing your houseplants to dry out a bit between watering can help to slow down or stop an infestation.

Moreover, let the top inch or two of the soil dry out before watering again, and try to go as long as possible between waterings.

Gnats may be deterred from laying their eggs when the soil is dry on the surface.

Mosquito Dunks with beneficial Bacteria

You can use mosquito dunks to keep mosquito larvae from populating fountains, animal troughs, fish ponds, and other small bodies of water.

Furthermore, the product consists of a dry pellet containing a type of bacteria: Bacillus thuringiensis.

It is the subspecies of isrealenia which is beneficial bacteria that infects and kills the larvae of flying insects including:

  • mosquitos
  • fruit flies
  • fungus gnats

To use mosquito dunk, follow the steps below:

  • fill up a gallon jug or watering can with clean water and toss in a mosquito dunk
  • it is a good idea to break up the dunk a bit before placing it in the water
  • or you can wait for it to soften before breaking it apart
  • let the dunk soak in the water for as long as possible at least overnight
  • remove it from the water, you can also reuse the dunk
  • use this water for fungus gnats-infested plants

The bacteria present in this will leech into the water and will infect and kill the larvae that come in contact with it in the soil

Make sure to repeat this process every time you water your plants for at least a few months.

Other Prevnetion Tips

Some other prevention tips are:

Cover Drainage Holes: Though gnats often remain near the tops of the pots, they may find their way to the drainage holes on the underside of the pot.

And there they can start laying eggs too.

If this happens, cover the drainage holes with a piece of synthetic fiber to prevent the gnats from getting in or out of the hole.

however, also let water pass through freely. make sure to attach with tape or rubber bands.

Cover Exposed Soil with Sand: Some people report that covering the soil of their houseplants with a layer of about 3/4 inch of thick sand can help prevent fungus gnats from accessing the soil and laying eggs.

This can also be an effective remedy deterrent if you use it in conjunction with other preventive methods above, especially covering the drainage holes.

Final Thoughts

Fungus gnats are small flies that feed on rotting organic matter and are a part of a healthy balanced ecosystem and harmless insects. However, in case their population increases, they can cause damage to your houseplants. With the help of preventive measures and consistency, you can control the infestation.

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