“I would very much appreciate an answer to my question… specifically… which of your Black Gold soil products contain perlite/vermiculite as I have learned this is best [for fungus gnat problems]. I am also aware that organic soil may perpetuate the fungus gnat problem as well. Since I have been having a terrible problem with fungus gnats as a result of having many plants, I need soil which would not promote these flies. I have eliminated all with the use of sand but must soon do replanting and am apprehensive about purchasing the wrong type of soil. After having read that peat moss is not the best for this problem, I would like to know which of your soils you would recommend.” Question from Barbara
Answer: Fungus gnats are so annoying with their root-eating larvae and pesky adults! They are a common problem that most indoor gardeners experience. They come in through open windows or doors, open potting soil packages, or newly potted plants.
Fungus gnat management is a cultural matter and not soil dependent. All potting soils must contain organic matter, be porous, and hold water well for effective root growth, and any soil that’s moist and high in organic matter will attract fungus gnats. But, don’t despair! Follow these simple cultural guidelines, and you can easily stop fungus gnats from breeding on the surface of your potting soils.
Fungus Gnat Deterrents
First, you need to know what deters fungus gnats:
- Dry soils;
- Fast-draining soils with inorganic additives, like perlite, vermiculite, and sand;
- Inorganic soil covers, like pebbles, coarse sand, chicken grit, or diatomaceous earth (Some swear by the gnat-killing power of diatomaceous earth!);
- Pyrethrin sprays approved for organic gardening.
Fungus Gnats Management
Now that you know what fungus gnats dislike, let’s talk management. The yucky larvae feed on plant roots and soil surface algae only in the first 1 to 1.5 inches of surface soil, so this is your management target area. They also breed quickly, going from eggs to adults in as fast as 17 days, depending on the temperature (they like warmth). Follow these home integrated pest management (IPM) steps, and you should see results quickly:
- Repot badly infested plants in fresh mix. Black Gold All-Purpose Potting Mix and Cactus Mix are both good, fast draining choices;
- Spray soil surfaces with pyrethrin spray;
- Cover the soil surfaces with at least 1-inch of inorganic soil cover (I recommend diatomaceous earth.);
- Bottom water all of your plants to keep soil surfaces dry and encourage deep rooting;
- Allow plants to dry somewhat between watering;
- Use yellow sticky traps to trap adult gnats.
I hope that these tips help you manage your fungus gnat problem.
Happy gardening!
Jessie Keith
About JESSIE KEITH
Plants are the lens Jessie views the world through because they’re all-sustaining. (“They feed, clothe, house and heal us. They produce the air we breathe and even make us smell pretty.”) She’s a garden writer and photographer with degrees in both horticulture and plant biology from Purdue and Michigan State Universities. Her degrees were bolstered by internships at Longwood Gardens and the American Horticultural Society. She has since worked for many horticultural institutions and companies and now manages communications for Sun Gro Horticulture, the parent company of Black Gold. Her joy is sharing all things green and lovely with her two daughters.
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This site may contain content (including images and articles) as well as advice, opinions and statements presented by third parties. Sun Gro does not review these materials for accuracy or reliability and does not endorse the advice, opinions, or statements that may be contained in them. Sun Gro also does not review the materials to determine if they infringe the copyright or other rights of others. These materials are available only for informational purposes and are presented “as is” without warranty of any kind, express or implied, including without limitation warranties of merchantability, fitness for a particular purpose, and non-infringement. Reliance upon any such opinion, advice, statement or other information is at your own risk. In no event shall Sun Gro Horticulture Distribution, Inc. or any of its affiliates be liable to you for any inaccuracy, error, omission, fact, infringement and the like, resulting from your use of these materials, regardless of cause, or for any damages resulting there from.
FAQs
A peroxide solution apparently kills larvae and eggs on contact, effectively killing off all infant gnats and disrupting the lifecycle. You should be able to buy hydrogen peroxide from any high street pharmacy or online. Mix 1 part 9% hydrogen peroxide with 6 parts water.
What kills fungus gnats instantly? ›
A peroxide solution apparently kills larvae and eggs on contact, effectively killing off all infant gnats and disrupting the lifecycle. You should be able to buy hydrogen peroxide from any high street pharmacy or online. Mix 1 part 9% hydrogen peroxide with 6 parts water.
What mixture kills fungus gnats? ›
Mix four parts water with one part hydrogen peroxide and soak your soil with the solution. Neem oil can also be diluted with water and applied to the soil to kill larvae. You can also use neem oil as a spray to kill adult flies on contact.
Will coffee grounds kill fungus gnats? ›
Coffee grind is great at removing gnat infestations. Dry the grind thoroughly – this will prevent mould from forming – and spread it over the potting soil. A thin layer will keep the female gnats from laying their eggs. Additionally, the coffee can fertilise your plants.
What repels fungus gnats? ›
The only way to get rid of gnats without killing them is to repel them with scents they don't like: vinegar, vanilla, pine oil, peppermint, lemon, eucalyptus, and lavender. Even dryer sheets could help. Of course, the first line of duty would be to get rid of the infestation's root cause.
Will hydrogen peroxide hurt my plants? ›
Hydrogen peroxide is effective in eliminating existing infections, but if used too much it will “sterilize” the entire potting soil killing not only the “bad” organisms but also the “good” ones and can even burn the roots if not diluted.
How to get rid of gnat infestation? ›
Here are six methods to try if you need to eliminate gnats in your home:
- Place Sticky Traps.
- Trap Them With Apple Cider Vinegar.
- Use Your Fresh Fruits or Red Wine.
- Turn on Your Fan.
- Clear Your Drains and Garbage Disposal.
- Hire an Exterminator.
Believe it or not, the solution to your fungus gnat problem may already be sitting inside your medicine cabinet. A diluted solution of Hydrogen Peroxide and water poured directly onto the soil will kill fungus gnat larvae on contact and help stop the gnats' life cycle.
How do you make homemade fungus gnat spray? ›
Homemade gnat killer spray: A mixture of half a cup of water, half a cup of isopropyl alcohol, and a teaspoon of dish liquid can be filled in a spray bottle. This mixture can be sprayed on the gnats directly to kill them.
Does cinnamon get rid of fungus gnats? ›
How does cinnamon deter gnats? 'While cinnamon conjures up memories of Christmas and gingerbread for most, the smell repulses gnats and other insects like ants and spider mites,' says Garden Bench's expert Chris Chan. 'It is a humane method of getting rid of gnats in the house, as it won't kill them.
Steinernema feltiae is more effective against fungus gnats than other commercially available nematode species. Mix Bti or nematodes with water, and apply as a soil drench, or spray onto media using a hand-pump spray bottle or other spray equipment, following label directions.
What eats fungus gnats? ›
Parasitic wasps (Synacra flies) are a natural enemy of fungus gnats and may be seen on yellow sticky cards, especially in unsprayed greenhouses. Entomopathogenic nematodes, soil dwelling predatory mites, rove beetles are all part of a biological control program for fungus gnats.
Will baking soda kill fungus gnats? ›
Fungus gnats are also sensitive to baking soda. An ideal household remedy. Sprinkle some baking soda on the soil and then moisten it. The larvae that are in the soil absorb the baking soda and die over time.
Can you get rid of fungus gnats forever? ›
Eradicate your fungus gnat infestation for good with the following method: Put up a bunch of sticky traps, top-dress the soil with sand and do nematode soaks every 10 to 14 days until the problem is resolved. Also, stop overwatering your plants and eliminate any unnecessary sources of moisture. That's it.
Do dryer sheets repel gnats? ›
Fungus gnat adults are highly attracted to moist growing medium; however, dryer sheet repellency, as demonstrated in experiments three and four, clearly overcame any attraction to the moist growing medium.
What smells do fungus gnats love? ›
Gnats are fond of certain pleasant smells as well. These include sweet and fruity scents like those used in many shampoos, lotions, and perfumes.
Is neem oil or hydrogen peroxide better for fungus gnats? ›
Neem oil is a natural pesticide that's pressed out of the seeds of neem trees. Just like hydrogen peroxide, neem oil can be diluted with water. Unlike hydrogen peroxide, neem oil solutions also kill mature fungus gnats and thereby speed up the process of eliminating the pests for good.
Can you spray vinegar on fungus gnats? ›
If you just have a couple scouts checking out the accommodations—as in, the gnats aren't swarming yet—fill a spray bottle with a cup of water, a tablespoon of vinegar, and a few drops of liquid dish soap and give it a good shake. Spritz gnats in flight to put an end to the infestation before it begins.
What is a natural spray for fungus gnats? ›
Homemade gnat repellent spray: A mixture of dish soap, water, baking soda, and vinegar can be filled into a spray bottle. The mixture should contain a few drops of dish soap, a tablespoon of vinegar, and baking soda per cup of water. A few sprays of this mixture is an effective gnat repellent.
