Fungus Gnats - Why are they a problem?

Gotrox · May 2, 2014

Just cover the tops of your poor seedlings containers with an inch or so of dry sand and bottom water.

Gets rid of them in a week or so.

willard3 · May 2, 2014

I grow in aero and have fungus gnats in my compost.

No problems at all from fungus gnats at all.

hottoddy · May 2, 2014

Also, when I see fungus gnats indoors on seedlings, aphids and mites soon follow. I think they help spread them.

solid7 · May 2, 2014

hottoddy said:
Also, when I see fungus gnats indoors on seedlings, aphids and mites soon follow. I think they help spread them.

Not sure about that... For all the fungus gnats that I have, I've never had a problem with either aphids or mites. I suppose it's possible, but I'd be more inclined to believe that other pests would be attracted to a wounded or compromised plant, more than the likelihood of a symbiosis with fungus gnats.

Valleyman · May 2, 2014

Jeff H said:
MX is pretty much right on target. Gnats vs. seedlings = plant death. gnats vs. larger plants. = no real issues if there aren't too many.

I've pulled dead seedlings that have been attacked by the gnat larva. There isn't much more left than their stem. Roots are all but gone.

I have/had the same issue. Plants were not growing as quickly as expected and learning about the larva, I pulled my plants and just about all the hair roots were gone and only the larger main roots were still there. I re potted in soiless mix. Hopefully that will get the plants to be teenagers

solid7 · May 2, 2014

Valleyman said:
I re potted in soiless mix. Hopefully that will get the plants to be teenagers

I would watch it close. The one and only time the larva got me, was when I used the foam grow plugs. As I theorized earlier, I think they may pose the biggest problem when the least amount of organic material is available. Whether that's synthetic materials, or small seed trays...

John1234 · May 2, 2014

solid7 said:
Not sure about that... For all the fungus gnats that I have, I've never had a problem with either aphids or mites. I suppose it's possible, but I'd be more inclined to believe that other pests would be attracted to a wounded or compromised plant, more than the likelihood of a symbiosis with fungus gnats.

I believe what he meant, was that a plant that is stressed (say, larvae perpetually chewing roots/potentially spreading disease) is more likely to be a target for other pests. Fungus gnats are easily large enough to hitchhike other bugs around, whether pest or bene.

rory · May 13, 2014

Interesting, I myself have a particular dislike for fungus gnats, mainly because they have spread to all my potted pepper plants. Growth has slowed and any healthy root hairs have been replaced by brown, root rot, root tips.
I am in need of help, something homemade and something which wont affect my organic grow medium.

Thanks

Weed · May 13, 2014

Break a mosquito dunk in half and soak it in a gallon of water. Water plants with that. Hang sticky traps.

D3monic · May 13, 2014

I had issues with them indoors in soil. Seemed like no matter what brand soil I bought it was loaded with them. Mosquito dunks, diatomaceous earth and thick layer of sand on top pot help keep the pop down. Nothin worse than a bunch of gnats in the house...well spider mites but still

solid7 · May 16, 2014

rory said:
Interesting, I myself have a particular dislike for fungus gnats, mainly because they have spread to all my potted pepper plants. Growth has slowed and any healthy root hairs have been replaced by brown, root rot, root tips.
I am in need of help, something homemade and something which wont affect my organic grow medium.
Thanks

Where exactly are you located? Are you growing indoors or out? I'm only aksing because my growth has slowed, too, but it's because of the heat...

Since fungus gnats only live in the top 2-3" of soil, a potted plant with decent growth should not be slowed down a bit by fungus gnats. Are you sure there isn't another culprit?

Valleyman · May 22, 2014

Back again. After repotting my almost root less seedlings, now they go back and forth from the greenhouse to outside getting fresh air and sunshine, though still not planted they are still alive but growth is extremely slow. Their root systems have barely recovered so I just ordered Dyna Gro K-L-N rooting concentrate. They claim it'll help weak root systems. Under 10 bucks, at this point I'll give it a try.

Fortunately, roughly 65-75 % of my plants are fine but now I'm on a mission to get the remaining guys back. Working against the clock now too. I want to plant in a couple of weeks.