Fungus Gnats: the Cause, the Problem and the Answer

By Chad Garbet
Published: September 1, 2016 | Last updated: April 23, 2021 03:02:56
Key Takeaways

Nothing is worse than finding pests in your garden or your growroom, and it’s no different when those pests are tiny fungus gnats.

Fungus gnats are a common nuisance to many gardeners. This tiny black creature with a slender thorax (much like a miniature mosquito) is annoying when in the area and its larvae eat away at precious root growth, destroying plant structure.


Even the smallest amount of fungus can attract them, and infestation can happen quickly—often before most can notice. The larvae—translucent, greyish-white mini worms with black heads—hatch from small grey silk-like cocoons.

Any signs of any of these creatures can stress gardeners out, and most people will immediately think of turning to pesticides. Now, that might be a good option, but one should always remember that a pesticide is a poison. So, that being said, pesticides should always be used as a last resort.


Luckily, we have other options. There are now natural-based gnat products on the market. Also, as humans have dealt with pests naturally for thousands of years, it is possible to take things into your own hands. Pesticide-free options are almost always an easy fix and, being the busy gardener that I am (like most gardeners), easy sounds like it saves some of that precious time.

First, you have to think like the gnat. Be the gnat. Now, that we are gnats: aren’t you kind of hungry? After all, we see that there’s a bunch of hungry gnats out there on our plants, so now we have to figure out what they eat and how to get rid of that. They are called fungus gnats so that saves us some brainstorming. Fungus is the primary food source for gnats. These little buggers are attracted to it like the scourge.

Fungus might not even be apparent at the time, but these pests smell it out. Small amounts of fungus are easy enough to clear out. In bad fungus cases, we might want to move directly out of the growroom. For small fungus infestations, an easy solution is baking soda. It’s in most refrigerators, cupboards and pantries, so it saves us a bit of time and some money.


Mix about a level tablespoon of baking soda and a single drop of dish detergent per quarter gallon of water, remembering to shake well. Spray this on your plants lightly about once every three days for about two weeks. The baking soda raises pH, thus causing fungus to stop its growth, and the detergent makes sure the area is clean, thus stopping anymore fungi from forming.

Now that the fungus gnat’s main food source is gone, hopefully no more fungus pests will be attracted. After this, the current population’s numbers will start to dwindle down. You might find the few stragglers, but this is okay; home remedies sometimes take time.


Now, like Superman, the fungus gnats have a kryptonite. It’s cinnamon. Those little guys can’t stand it. You can see them squirm when you lightly dust the soil with the cinnamon. Also, the same effects are present when you water with chamomile or spearmint teas. (I personally think the cinnamon works the fastest.)

Gnats will literally flee the scene, leaving only a few egg sacks. However, you have to be persistent and repeat a few times or they will multiply and come back. After a few weeks of treatment, you will see the fungus gnats are not present. To make sure the little pest’s don’t come back, make sure your garden or growroom is always clean.

For heavily effected plants, these home remedies might not work and pesticides might have to be applied. Remember, this is only a last resort; try to do the all-natural ways first. Still, there is another way to get around pesticides and home remedies. Mother Nature provides us with more bugs to fight against the pests.

Bugs that eat other bugs… seems pretty neat to me. Nematodes and hypoaspis miles are two great warriors to use to get revenge on the fungus gnats. The nematode is a parasitic round worm that enters the pests’ larvae and release a bacterium into the host, killing it within 48 hours. Hypoaspis miles is a preditory mite that also feed on the young of the fungus gnats. Another bug that can work is ladybugs; if no aphids can be found, these guys will resort to other pest (they’re also a fun bug to have around).


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Written by Chad Garbet

Profile Picture of Chad Garbet
Chad Garbet considers plants to be the most fascinating things on our planet. Trying to get information about growing plants out to the general public is his goal. Chad wants to see jungles inside our major cities and on every corner on every street.

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