Fungus Gnats

Does anyone have a good solution to getting rid of fungus gnats. At least I think they are fungus gnats. I started some tomatoes and peppers on my kitchen counter under a grow light and there are what look like fruit flies on the soil. I had them last year and bought an over the counter bug repellant (I don't remember what it was called) but it didn't work very well. I have heard of cinnamon for fungus, but I don't know of anything to get rid of the gnats.

Can someone give me some direction please?
Thanks
Ruth

Hi Ruth,

Mosquito Dunks are also effective against Fungus Gnats because they are both "flies"and susceptible to the same things. The Fungus Gnats lay eggs on your soil, which hatch out into maggots that feed on things in your soil, including plant roots. The maggots are what do the damage. The maggots pupate, which hatch out into more adult Fungus Gnats, to continue the life cycle.

I currently use Imidacloprid to prevent Fungus Gnats in my indoor plants, but before Imidacloprid I used the Mosquito Dunks. If you are an organic gardener, you will want to use the Mosquito Dunks and not the Imidacloprid, which is a broad spectrum insecticide.

ZM

So if I have a fruit fly trap (never tried one before) do you think they will go into it? I set it out this afternoon and all I see on it is a Japanese beetle.

My tomatoes are a little wilted, is that a symptom of having fungus gnats? How thick to do you it on the soil, enough to cover? I think this is what I used last year and it didn't work very well, maybe I wasn't using enough.

Hi Ruth,

I am unfamiliar with the "fruit fly trap" you have, so I have no idea whether the fungus gnats will go into it. Fungus Gnats are not Fruit Flies. Or what the significance is of a Japanese beetle "on it".

However, it is not the Fungus Gnats themselves that damage your plants, but their maggots. Their maggots burrow under the surface of the pot medium, or soil, if that is what you are using in the pots. The Fungus Gnat maggots eat your plant's roots.

I am not sure I know what you mean by "How thick to do you it on the soil.."Are you talking about the Mosquito Dunks? If so, you powder a piece of dunk and mix it in water and water your plants with the Mosquito Dunk liquid. The Mosquito Dunk liquid will soak into the pot medium (soil?) and kill the maggots that are burrowing around in potting medium (soil?) in the pots.

We seem to be having a communication problem here. Maybe it will help if you just read this Wikipedia page:
https://en.wikipedia.org/wiki/Fungus_gnat

ZM

Hi Ruth,

I am unfamiliar with the "fruit fly trap" you have, so I have no idea whether the fungus gnats will go into it. Fungus Gnats are not Fruit Flies. Or what the significance is of a Japanese beetle "on it".

However, it is not the Fungus Gnats themselves that damage your plants, but their maggots. Their maggots burrow under the surface of the pot medium, or soil, if that is what you are using in the pots. The Fungus Gnat maggots eat your plant's roots.

I am not sure I know what you mean by "How thick to do you it on the soil.."Are you talking about the Mosquito Dunks? If so, you powder a piece of dunk and mix it in water and water your plants with the Mosquito Dunk liquid. The Mosquito Dunk liquid will soak into the pot medium (soil?) and kill the maggots that are burrowing around in potting medium (soil?) in the pots.

We seem to be having a communication problem here. Maybe it will help if you just read this Wikipedia page:
https://en.wikipedia.org/wiki/Fungus_gnat

ZM

Hi Zen Man
Sorry to take so long with a response.

I got some Mosquito bits and sprinkled them on top of the soil. I haven't seen as many fungus gnats since then. I was just unsure of the Mosquito Dunk, if you put it on top of the soil or mixed it with water. I think the bits are taking care of it.
Thanks

Hi Ruth,

Yes, I think the Mosquito Bits have the same biological "fly killer" that kills Fungus Gnat larvae. I encountered Fungus Gnats many years ago before the availability of Mosquito Bits, so I powdered the Mosquito Dunks to get something I could use. I added some of the powdered Mosquito Dunks to a gallon of water, and applied that water to the growing medium in my pots. It takes a week or more to break the life cycle completely, but the biological kill of the larva is prompt, and they, not the flying gnats, are the actual problem. You could add the Mosquito Bits to some water and apply that water to your pots. But applying just the Bits works too, as you have discovered.

ZM

Thank you ZM, I always appreciate any advice. People with experience are the best source.

I have used Mosquito Bits but then after a while the gnats came back in my house plants. So I just used Diatomaceous Earth on the plants and it seems to be working. I just sprinkled the DE on the soil surface and now just a few bugs are left flying around and going to put on another application and I think that will do it. DE is a powdery rock that kills bugs but perfectly safe for humans you can even eat it. I would try this plus you can sprinkle it around your house if you have ants or any bugs!

Thank you dancer!! The mosquito bits worked for a while, but I noticed a few gnats again the other day. My tomatoes are pretty sick looking, don't know if it's from the gnats or something else. I will try the DE.

I seem to be having success with drenching the top 1/2 inch of soil with hydrogen peroxide (using a spray bottle) as well as coating the top of the soil 1/4 inch of with perlite, but you can use vermiculite and COURSE sand(not sandbox sand) from what I hear.

Too early to tell if it's going to work long term, but seems to be. The peroxides does something to the maggots and makes them not turn into adult flies from what I understand.

I do not know about indoor use but I have these around my outdoor pond each year. I use a product called Gnatrol. It is a bacillus that is mixed with water and poured over the soil in the affected area. It kills the larvae which eat the roots of plants. The gnats themselves that have matured only live a few days . Once the eggs and larvae are gone, they will die off. As I mentioned, I do not know about indoor use.

I think that the Gnatrol, Mosquito Bits, and Mosquito Dunks all contain the same bacillus as an active ingredient. I am not a fan of Diatomaceous Earth -- some grades of it are potentially harmful if you should inhale any of the dust. The peroxide probably should be diluted, although the commercial version is already diluted to 3%. The Perlite, Vermiculite, and coarse sand might be unfavorable to the maggots, but that could be expensive if you have a lot of pots. The bacillus method is probably the most cost effective solution.

I use Imidacloprid systemic insecticide to start off the season with my indoor zinnias, to prevent aphids, and thrips, as well as fungus gnats. In the absence of outdoor enemies, aphids and thrips can have population explosions indoors in indoor zinnias. And I prefer prevention rather than cure for fungus gnats.

ZM

I guess this thread is complete.

ZM