fungus gnats - please help!!!

squeeziemonkey(z5 Chicago)April 18, 2006

Fungus Gnats are invading EVERY pot I have! I am sprouting seedlings and now they are getting into them as well!

There are some really expensive Fungus Gnat products but I canÂt spend that much and donÂt want to kill the worms in my pots!

Does anyone know how to get rid of these G.D. Bugs??


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Tell us what plants you have and their size. I'll help you switch to subirrigation in soil based media or clay pebble hydroculture. It's easy to do and will cost very little...mostly some of your time. I'll post some how-to-do-it pictures.

If you change to measured subirrigation you will never have fungus gnats again. Promise!

    Bookmark   April 18, 2006 at 6:03PM
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Squeeziemonkey, IÂm a hydroculture addict myself but in case youÂre not ready (or interested) in switching methods right now and simply asking for some advice, IÂll oblige as best as I can.

Below is a copy of a recent post I made (too lazy to retype the same stuff :)

"You don't need to use any special chemicals or treatments with these pests because no matter how you treat this problem, if you don't cut down on the watering, they will return...again and again and again...

If you're looking for a natural remedy, the most natural (and highly successful) one is dehydration. You don't have to stop watering plants but you have to only water when they really need it. The top layer of soil (about 2 - 3 inches, sometimes more depending on pot and plant) should feel dry.

Fungus gnats favour the top soil. If you keep it constantly moist they will keep coming back. And it's not the adults that are a problem. They don't cause much damage beyond flying up your nose. But their pesky offspring can be quite detrimental, especially to the roots of the plant in question. Since fungus gnats multiply rapidly - terribly rapidly, in HUGE numbers - it's best to try to control the situation before the arrival of the next generation and the next... When there's no wet soil on top, the fungus gnats start to vanish because they dehydrate.

So no matter how you look at it and whether you do or do not use chemicals, sprays and treatments, if you don't improve watering methods you'll be treated to sequels of "The return of the Fungus Gnats".

A well-draining soil is best as well. If you're using a heavy, rich, black soil you may want to change that too. Thick, slow-draining soil holds too much water for too long and is an invitation to bugs and rot."

In summary: Dehydrate the little ^&%&%&%!

Hope that helps!

I have a question: "You have worms in your pots? Earth worms?? If so, why?" Just curious... :)

And just for the record, when greenscaper says youÂll never have fungus gnats again with the hydroculture method, heÂs right. Never, ever, ever again You will never see them again, youÂll never see any soil bugs again...never, ever...

    Bookmark   April 18, 2006 at 9:09PM
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"Gnatrol" is not too expensive and contains a natural bacteria harmful only to the gnats (it is not a chemical pesticide). I have used it with great success. :)

    Bookmark   April 18, 2006 at 10:46PM
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I had them everywhere several months ago. I just repotted into a better soil and stopped watering so much, and mine went away. If you search here, though, you'll find some easy, natural remedies, including putting yellow papers with vaseline around to catch them, and cups of apple cider (I think that was it...) Anyway, try searching the forum!

Good luck,

    Bookmark   April 19, 2006 at 12:25AM
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Further don't really need to make any radical changes. Merely subirrigate your soil based plants by installing them in a watertight cachepot with a pad of polyester backing (aka batting) material (an "Aquapad") at the bottom. This will wick the water up into the soil system by capillary action. The key is to use a measured amount of water and never add so much that the soil surface is wet or moist. It should remain dry at all times.

Subirrigation encourages healthy root growth in the lower section of the container. The soil surface dries out but not the root system so there's no loss of turgor pressure. The result is the plant is happy but the fungus gnat larvae are not. They're d.e.a.d. No problem!

NL mentioned the worms which I overlooked. I hope you're not using outdoor native soil ("dirt") for containerized "houseplants". That's not a good idea and the worms are best left outdoors where they will do some good.

Dehydrating the fungus gnat larvae is a good idea but with top watering there's also a high risk of dehydrating the plant too. It is not a good idea to "dehydrate" a plant to the point of wilt. It is very easy to damage the plant tissue when turgor pressure is lost this way.

    Bookmark   April 19, 2006 at 10:18AM
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squeeziemonkey(z5 Chicago)


I put the Worm's in the pots so that they can produce the great "Worm Castings".

I went to a store and got a container of Bait Worms which, according to my research, are great little buggers to keep in compost piles and such.

I save up all my tea bags, a handful of shreaded paper now and again, used (Bitter's Removed) Coffee Grounds, some egg shell's I grind in a coffee grinder, (For the plants that like high calcium levles.) and add them to the top 2 to 3 inches of soil once and a while for them to eat.

I know that they are happy because when I see them at the bottom hole of the pot sometimes and have found baby's in the bottom of the sink when I water in the bathroom sink once and a while and I then move the new one's to different pots inside or into my outdoor plant's.

I know you can BUY worm casting's so I figured why not put them into the pot with "worm food" and let them live happy lives in controled environments? Then they add oxigen to the soil and fertilize year round (In the indoor plants at any rate) while doing what worms do best...Digging and eating!

They have been kept alive and breeding for more then a year now!!!

I'm gonna start a "worm" post for people to give me their opinion on this...

Thanks again guys!

    Bookmark   April 19, 2006 at 10:36PM
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ara133(central PA)

Sorry, I realize this is old, but if you're still having the problem - try hot water! I just had an awful bout with these buggers, and nothing worked until I replanted almost all of my plants into a high sand mixture for better drainage, and watered with hot water. There are some studies reported online that state the fungus gnat larvae die at lower temperatures than what will kill the plant roots. I've just been using water that is warm to the touch. The gnats have been cut down considerably! Good luck :)

    Bookmark   February 4, 2007 at 4:43PM
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ara133(central PA)

Oops - forgive me, I didn't realize you had "good" worms in your pots also :) Maybe the hot water isn't a great idea, but if you have any plants that don't have helpful worms, give it a try!

    Bookmark   February 4, 2007 at 4:44PM
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squeeziemonkey, you have two great projects: growing plants and raising worms, but you will never, never be successful doing them together. To keep the worms happy, you have to keep them in a large container and feed them things that will definitely draw gnats. No way around it! I keep cheesecloth over my worm container to keep the gnats from invading my house. Then when you have enough worms to produce castings, you can separate the worms from the castings and feed your plants with the great castings. There is a great book out called "Worms Eat My Garbage". Sorry I can't remember the author. This a a great help for anyone that wants to raise worms.

    Bookmark   February 6, 2007 at 3:25PM
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CINNAMON from your kitchen cupboard will be the killer !! I hate using chemicals so I chose this option . I guess I was over watering and the result for that WAS fungus gnats . ICK !!! Somewhere in one of these fungus gnats forums, Peggy suggested cinnamon . All though she had never tried it , I did . I already knew cinnamon is a natural fungicide and very good for humans but not for plants . It was available and ready to use . When I eye-balled these little buggers I was watering my plants . They come to the surface for air due to the water . I had no idea what they were or how they got in the soil . I hopped on-line and found out right away . I handled the problem by sprinkling quit a bit of cinnamon on the surface of the soil , then used the handle of a spoon to mix it into the soil . Also I sprayed a paper towel with water, then sprinkled cinnamon on the towel and wiped the rims and inside edges of each planter. ( Use a separate towel for each pot ). I love an experiment so I was on my way . I then had to wait for all of my 10 plants to dry out quit well . Some took a few days longer due to the size of the planter . In all about 3-weeks . I sprinkled cinnamon again on the surface ,not too much this time , then watered only half the amount that I had been watering . My plants are very happy now , they are loving every minute of it !!! Also they all have new growth . Thanks to this forum , Peggy and a little research , the buggers are GONE !!!!!!

    Bookmark   February 3, 2008 at 12:07PM
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paul_(z5 MI)

vinniegirl, just a clarifying point -- the cinnamon didn't kill off the gnats. As you mentioned, cinnamon is a fungicide. What occurred is the fungus growing in you soil was killed off depriving the gnat larvae of their food source [that's what fungus gnat larvae eat -- fungus] Either way though your results were the same. :)

Personally I rather miss the lil buggers. Used to have a bunch in my bog terr. Then my butterworts and sundews grew up. End of gnat population. Now my poor lil cps have had to go over a year without a meal. :)

    Bookmark   February 5, 2008 at 8:58AM
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rhizo_1 (North AL) zone 7

Fungus gnat larvae eat organic matter. Much of the stuff our original poster was piling on top of the poor plants encouraged well as the worm castings. Also,most potting mixes are composed largely of peat moss, which the larvae will also feed on. And of course, the tender roots of our plants!

    Bookmark   February 5, 2008 at 1:15PM
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Put Mosquito dunks in your watering can. It contains BT which is safe for you and your pets but kills the larvae. That and sticky traps keeps mine in control.

    Bookmark   February 6, 2008 at 9:31PM
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i use Cigarette tobacco, 1 cup Cig. tobacco 2 qrts water, soak 24hrs strain and squeeze strained tobacco into container, water plants., works great and not harmful., works for alot of Dif. pests also

    Bookmark   December 3, 2012 at 1:37PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

Hi Rivvers, welcome to Gardenweb.

    Bookmark   December 3, 2012 at 5:49PM
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diatomaceous earth food grade is an excellent source to get rid of gnats ants roaches waterbugs bed bugs and safe for humans and pets not harmful to earth worms but any bug with exoskeleton it will dehydrate them

    Bookmark   August 6, 2013 at 12:31PM
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