Ask a Question forum: How to get rid of fungus nats\soil flies

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Name: Alex Junge
MN st paul, (Zone 4a)
Plantsmylove
Mar 10, 2017 12:20 PM CST
I noticed that I have large numbers of flies gnats in my room and am told I need to get rid of them I know moisture helps them but I have plants which need moist soil such as joboticia and banana shrub and corpse flower.
Is there something I can add to the water to kill the flies.



Thanks
Name: Karen
NM (Zone 7b)
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plantmanager
Mar 10, 2017 12:27 PM CST
Here is a previous article with a lot of information.
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Name: Philip Becker
Fresno California (Zone 8a)
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Philipwonel
Mar 10, 2017 1:26 PM CST
1 part 3% peroxide to 4 parts water.
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Name: Tiffany purpleinopp
Opp, AL 🌵🌷⚘🌹🌻 (Zone 8b)
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purpleinopp
Mar 10, 2017 1:33 PM CST
Gnats live in soil, so repotting, removing the old soil & replacing with new would be an instant solution.

Aside from that, killing the larvae w/o replacing the soil can easily be accomplished by adding BTi to the water given to plants. It kills the larvae in the soil and breaks the cycle. Products called mosquito dunks & mosquito bits are popular for this.
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[Last edited by purpleinopp - Mar 11, 2017 9:00 AM (+)]
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Name: Baja
Baja California (Zone 11b)
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Baja_Costero
Mar 10, 2017 11:16 PM CST
This came up recently on another thread and I spoke up in favor of a low tech solution: flypaper. I have tried chemical and biological agents (which do work) but have come back to good old fashioned sticky flypaper, which works for longer and leaves visible results.
Name: Barbalee
Amarillo, TX (Zone 6b)
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Barbalee
Mar 11, 2017 7:44 AM CST
The problem as I understand it is that the fungus gnats feed off the roots of plants. If the roots are tender (as in seedlings), the gnats can kill them quickly. I tried growing plants from seed last spring and lost most of them to the darn gnat problem. Fly paper will grab the adults, but the ones in the soil would be unaffected.
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Name: Elena
NYC (Zone 7a)
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bxncbx
Mar 11, 2017 8:01 AM CST
Barbalee try a combination of yellow sticky traps for the adults (they like the color) and Bt for the larvae. I bought Knock out Gnats (Bt) and they give you so much it's a lifetime supply for me.

You just have to make sure you use the Bt at the right time. When I notice the population of adults is falling off I start watering with the Bt. You may need a couple of their life cycles to get them all but it does work. I get them every year when I start seeds and so far I have not lost a single seedling despite a fairly bad outbreak.
Name: Karen
Southeast PA (Zone 6b)
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kousa
Mar 11, 2017 8:16 AM CST
I agree with Elena. I used most of the suggestions above before Bt but still had problems from daylilies seedlings dying off. Gnatrol (Bt powder form) when applied as directed eliminated enough gnats population that I saw improvement on my daylilies seedlings within 3 days.
Name: Baja
Baja California (Zone 11b)
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Baja_Costero
Mar 11, 2017 10:57 AM CST
No, the fungus gnats do not feed off the plants. They are not vegetarians (the hint is in the name). Other than the annoyance of little flying insects everywhere, the problem is that fungus gnats can rapidly spread soil-borne diseases from one plant to another. They serve as excellent vectors for plant pathogens. They are never going to kill your plants on their own.

The flypaper only kills the flying adults, meaning the larvae in the soil will continue to grow, so it will never totally eliminate the fungus gnat population. But it will control it in a very useful way. The stuff you put into the soil does not last forever (imidacloprid or Bt) and once it washes out you have to re-apply to continue to have control. The flypaper takes a really really long time to stop working, which you can basically tell by looking at it. I have tried each of these things and observed the results, so I speak from experience, not conjecture.

You will continue to have fungus gnats arrive in your container garden nearly constantly if you're like me and they arrive with new soil every time you pot a new plant up, or repot an existing plant. I think they are present in the potting soil. The steady trickle of new arrivals through this point of entry means they are always only a few generations away from a swarm. Smiling
[Last edited by Baja_Costero - Mar 11, 2017 11:02 AM (+)]
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Name: greene
Savannah, GA (Sunset 28) (Zone 8b)
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greene
Mar 11, 2017 11:04 AM CST
Baja_Costero said:No, the fungus gnats do not feed off the plants. They are not vegetarians


I agree with most everything you said Thumbs up except for the above quote. While the adult fungus gnats may not, the larvae do feed off the roots of plants.



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Name: Baja
Baja California (Zone 11b)
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Baja_Costero
Mar 11, 2017 11:05 AM CST
Okay, I stand corrected. Thank you. I have never observed this behavior with the plants I grow. Fungus gnats are certainly capable of thriving in soil with no plant roots whatsoever.
[Last edited by Baja_Costero - Mar 11, 2017 11:09 AM (+)]
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Name: Barbalee
Amarillo, TX (Zone 6b)
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Barbalee
Mar 11, 2017 11:10 AM CST
bxncbx said:Barbalee try a combination of yellow sticky traps for the adults (they like the color) and Bt for the larvae. I bought Knock out Gnats (Bt) and they give you so much it's a lifetime supply for me.

You just have to make sure you use the Bt at the right time. When I notice the population of adults is falling off I start watering with the Bt. You may need a couple of their life cycles to get them all but it does work. I get them every year when I start seeds and so far I have not lost a single seedling despite a fairly bad outbreak.


Whether the gnats fed off the roots or allowed some other pathogen to enter, I don't know. I used the Bt, but maybe not at the right time. That I don't know either! I used the yellow sticky paper, and it got most of the adult ones. All I know for sure is that I had a lot of gnats and most of the seedlings died. They were about 3-4" tall when the growth turned brown and fell off at the soil level. Either way, I lost most of them! But that's okay...lots of people have dealt with much worse.

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Name: Baja
Baja California (Zone 11b)
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Baja_Costero
Mar 11, 2017 11:13 AM CST
Damping off is one of the things that fungus gnats can facilitate as a vector.
[Last edited by Baja_Costero - Mar 11, 2017 11:14 AM (+)]
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Name: Cheryl
Texas (Zone 9a)
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ShadyGreenThumb
Mar 11, 2017 8:55 PM CST
I had fungus gnats in my tortoise habitat. I could not use insecticide. I used a mix of vanilla extract and water, and placed a small cup of it where Sheldon could not reach. I stirred up the soil and sprayed it lightly. I also wiped the glass walls with it. Gnats are gone.
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Name: Tiffany purpleinopp
Opp, AL 🌵🌷⚘🌹🌻 (Zone 8b)
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purpleinopp
Mar 12, 2017 11:19 AM CST
Bt (or BT), and BTi, are 2 different things, BTi is the one the kills FG larvae. I don't think anyone has said it's a 1-&-done, it may need to be used prophylactically/periodically, on a case-by-case basis.

If one is using a type of soil gnats like to lay eggs in, and new plants are brought in, or plants are put outside, they can come back. Gnats can fly in when someone opens a door. If left unchecked, an infestation will likely result in a dead plant, regardless of of a chain of events or not.

Aside from no longer killing plants, I don't have gnat issues since I stopped using peat moss.

I stand by repotting as the easiest, most economical instant fix, if it's just one plant. If one has a massive number of pots, treating the soil would probably be.
👀😁😂 - SMILE! -☺😎☻☮👌✌∞☯🐣🐦🐔🐝🍯🐾
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☕👓 The only way to succeed is to try.
Name: Baja
Baja California (Zone 11b)
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Baja_Costero
Mar 12, 2017 11:40 AM CST
purpleinopp said:Bt (or BT), and BTi, are 2 different things


Technically Bti is a type of Bt, in the literal sense that they are the same species of Bacillus. But Tiffany is right that it is the best type of Bt for this purpose. Mosquito dunks should work.
[Last edited by Baja_Costero - Mar 12, 2017 11:40 AM (+)]
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Name: Philip Becker
Fresno California (Zone 8a)
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Philipwonel
Mar 12, 2017 3:11 PM CST
I read that a layer of washed sand will take care of fingus gnats.
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