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How to Get Rid of Fungus Gnats safely

Get rid of fungus gnats now!  Personally, I have tried every other method recommended but with no success.  See how I get rid of fungus gnats effectively and safely!

How to get rid of fungus gnats is easy, natural but ongoing.   I tell you why you are never free of these plant gnats and I have links to what I use. But first…

What Are Fungus Gnats aka Plant Gnats

Fungus gnat adults are the grayish black, delicate little winged critters that resemble fruit flies or tiny mosquitoes.  They love humid and moist conditions. 

The adults are harmless yet so annoying. But they lay eggs and when they hatch the larvae feast on fungi, plant root hairs and other organic materials.  They are very harmful to seedlings, young plants and cuttings you are attempting to root. 

You may notice adults flying up when you water your plants.

Terra Cotta pots on window sill, how to control fungus gnats

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Related: Grow in the Dark, plants that grow in very low light

Why Fungus Gnats Persist

Fungus gnats persist because new plants you bring home and potting soils all have them. That is why you can’t get rid of fungus gnats once and for all.

Gardeners can’t get away from it.  It is part of the great circle of life, especially if you are an organic gardener.

Potting soils purchased at garden centers, big box stores and so on are all stored together. The potting soils are moist and full of conditions fungus gnats love to breed in. 

It is no ones fault.

If you have a fungus gnat problem it is not because you over water.  I roll my eyes each time I see someone say that.

Case in point, I was rid of the fungus gnats in my home. I suddenly noticed I had them again and wondered what was going on. I water on a consistent schedule and adjust as the needs of plants change because of environment and season.

Then I remembered I had brought home some herb plants that were on sale at a great price at a big box store and had placed them on my kitchen window sill until I could get them re-potted and into the greenhouse to grow on.

Sure enough they were infested with fungus gnats.

Sanseveria plant, Mother In Laws Tongue, Snake plant, how to control fungus gnats

What hasn’t worked to get rid of fungus gnats

When researching how to handle fungus gnats I came across many methods that sounded good but did not work for me when I tried them. (others may have found them effective, but I did not)

Letting the soil dry out. 

This did not work because a few of my plants got stressed and showed signs of it by getting brown leaf tips like my Peace Lily (Spathiphyllum)  Peace Lilies like constant moisture.

Also new cuttings just rooted and planted need to be kept moist to grow best so letting them dry out to the first two inches would be a death sentence for them. We are talking moist, not drenched but they do need the constant moistness to thrive.

Removing top soil and replacing with sand.  

If you get potting soil that is already infested then the larvae are deep enough to be noshing away. 

Sand is supposed to discourage the adults from laying eggs and continuing the cycle but if you read above on why fungus gnats persist you will see why this is just added work.

I did try it though but did not get the results I wanted. The rascals started to go in along the bottom drain hole instead of on top.

There are a couple things I have not tried which are an organic pesticide soil drench (Neem, I have it but don’t use it for plants in my home as I don’t care for the odor of it) or beneficial nematodes.

Seeds sprouting, how to control fungus gnats, FlowerPatchFarmhouse.com

What works to get rid of fungus gnats.

Crazy as it sounds sometimes I pasteurize my soil if I notice an excess of fungus gnats before potting up sensitive plants and cuttings.  Do I always do this?

No, but it has been effective for so many problems.

Buying sterile seed starting mix takes care of the need to pasteurize but I was starting seeds on a larger scale and wanted to use my own compost mix.

Not only does it get rid of the larvae present in just about any potting soil out there but it will also get rid of the pesky bacteria that can cause damping off when you start seeds. 

This temp is enough to get rid of the bad organisms without killing the good. 

How to Pasteurize Soil

Note: I no longer bother with pasteurizing when just repotting plants, I tell you why at the end of this article.

Pre-heat your oven to 200 degrees Fahrenheit. Pour up to 4 inches of your potting soil into a large baking pan (I like the large aluminum ones you can get at the Dollar Store) and put a meat thermometer in the center of the tray, deep into the dirt. Place the tray in the oven and keep an eye on the dirt’s temperature. Once the center of the dirt reads 160 degrees, bake for 30 minutes. Allow the dirt to cool thoroughly before using.

When I am in a hurry, I pour boiling water through the soil, in a wire sieve and let that do the work.

My Easiest and Main Weapon to combat Fungus Gnats

Yellow Sticky traps can be found here. 

Yep, these simple little yellow pieces of sticky paper.  They keep the population of adults down so they cannot lay eggs and repeat the circle of fungus gnat life.

Sticky trap on terra cotta pot of rosemary, how to control fungus gnats

They come with little wire spikes to stick them into the soil but I don’t use those. I peel one side of the paper off to reveal the sticky stuff.

Then lay it, sticky side up, on an edge of the pot that I have noticed gnats swarming up from when watering.

On my plants inside the house I see an outbreak typically the end of February and beginning of March so I set out traps.

After a few days I see them starting to pile up on the traps.

Fungus gnats on sticky traps on potted lavender cutting, how to control fungus gnats

To control fungus gnats inside my greenhouse I keep sticky traps out all year around. 

My greenhouse is where I re-pot plants, start seeds etc and I have my bags of potting soil or mix my own from my compost so fungus gnats get brought in constantly.

(I don’t like the odor of Neem drench so I don’t use it in my greenhouse either)

It sounds too simple but that really has been the easiest and most effective method to control fungus gnats.

I purchase my sticky traps at a local garden center. They can also be bought from Amazon and box stores.

Not only do they work for Fungus Gnats but also White Fly, Aphids and Leaf Miners.  More bang for the buck!

Some people make their own but the traps are so inexpensive that it is not worth the bother to me.

Some have mentioned that the traps can catch beneficial insects too but I have not had that be an issue.  Mostly I only catch the fungus gnats and recently a spider.


Be gone you pesky gnats!

Fungus gnats on trap, Control fungus gnats

Get Rid of Fungus Gnat Larvae With This

This is an update to this article.  I found out about this a couple of years ago and it works! 

Use these mosquito bits, it kills the larvae of the Fungus Gnats.

When you use the yellow sticky traps and the bits together you have a well rounded method to get rid of both the adults and the larvae.  Mix the bits into any new potting soil you use and you should see a dramatic reduction in any fungus gnats problem. 

So now I skip the pasteurizing if I am just re-potting some plants. Last year I did an experiment testing seed starting mix against my DIY potting soil. The results may surprise you, press here to see how it turned out!

A great garden read: Compact Plants for Small Gardens

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Potted plants with fungus gnats, how to get rid of fungus gnats

Happy Gardening!

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Luna

Thursday 1st of April 2021

Hello ! Thank you sharing this information. I just planted Dahlia flower bulbs and I noticed these tiny flies. I’m completely new to planting flowers, i am in need of much information and help I can get. Will the mosquito bits in the soil affect the newly planted flower bulbs? Thank you 🙏

Pamela

Saturday 3rd of April 2021

No, they won't harm the dahlia tubers or animals.

Raewyn

Saturday 6th of March 2021

I have a Peace Lilly and am starting again growing it because of Gnats and Neem Oil is horrible I used extra potting mix and repotted my plant but not right to the top has to grow again it is outside at the moment but I have these yellow sticky thing's they are good

Barbara

Friday 5th of February 2021

I love all your idea. I will be using them.

Linda Speers

Thursday 26th of March 2020

I tried this idea I found online - same idea as the sticky strips I brought some iris inside to get started for my daughters new home, so could have come from out side or the garden soil that was in the garage Combine 1/2 warm water, 2T apple cider vinegar, 1 T sugar and about 1/8 t Dawn dish washing liquid The cider vinegar attracts them, and the soapy water traps them Worked really well. I used a shallow container,.

Jayne Cambra

Sunday 24th of November 2019

I'm so glad I found this post. I have a spearmint plant that was attracting those gnats; actually I think it was the soil that I brought in from outside.

So to get rid of the gnats I ended up putting the plant (roots) in water instead. Now, I know what to do. Thank you again for this info.

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