How do I get rid of Fungus Gnats?

My little seedling plant is about 7-8 days old. Yesterday i noticed a small fly on my plant. Thought it was only one but I noticed that when I shake up my soil, more start crawling out and flying around. Fuck. So it seems like there have to be some fungus gnat larvae in my soil. My plant also seems to grow reeeeeally slow lately, I don't know if that stands in any relation to the gnats. It still looks healthy but I'm worried that it won't stay like that. I put up a few yellow traps for the gnats, and they actually do catch all of the gnats flying around, but as you probably know, it's the larvae that cause problems since they feel off of the plants roots which will eventually kill my plant.

What can I do about this? It's my first grow ever. I stopped watering and I'm now waiting for the soil to dry up, but I'll still have to water my plant in a couple of days. What can I do to completely get rid of gnats and what can I do to keep them away in the future so I don't have to deal with this again?

If it's of any importance, I'm using 4 CFL's in a cupboard, they're all about 10 centimetres away from the plant.

Thanks for your answers, I really appreciate it.

For future reference try the Search! There are too many threads on Fungus gnats to count!

Fungus gnats aren't that detrimental to plants; although they can affect really young plants. They mostly eat the dead, decaying matter in the soil but may potentially feast on fine root hairs. Usually they aren't a huge problem unless you let them get out of control.

They could come from outside, other houseplants you have, and I've even seen them fly out of the auxiliary/overflow drains in bathroom sinks (suggesting they lay eggs there as well).

The best solution is a biological control called Bacillus Thuringiensis israeli, a bacterium that makes a narrow spectrum toxin which kills mosquitoes, blackfly and fungus gnat larvae. Many products contain Bti, including Gnatrol. The most commonly available Bti product is Mosquito Dunks (or Mosquito Bits) which is sold at virtually every hardware/garden center.

If all you can get are the Dunks, break one of them up, soak it in a gallon of clean water for about a day and then water it in. Repeat every couple weeks. Mosquito Dunks/Bti is perfectly safe for seedlings.

Nullis said:

For future reference try the Search! There are too many threads on Fungus gnats to count!

Fungus gnats aren't that detrimental to plants; although they can affect really young plants. They mostly eat the dead, decaying matter in the soil but may potentially feast on fine root hairs. Usually they aren't a huge problem unless you let them get out of control.

They could come from outside, other houseplants you have, and I've even seen them fly out of the auxiliary/overflow drains in bathroom sinks (suggesting they lay eggs there as well).

The best solution is a biological control called Bacillus Thuringiensis israeli, a bacterium that makes a narrow spectrum toxin which kills mosquitoes, blackfly and fungus gnat larvae. Many products contain Bti, including Gnatrol. The most commonly available Bti product is Mosquito Dunks (or Mosquito Bits) which is sold at virtually every hardware/garden center.

If all you can get are the Dunks, break one of them up, soak it in a gallon of clean water for about a day and then water it in. Repeat every couple weeks. Mosquito Dunks/Bti is perfectly safe for seedlings.

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Thank you very much!

Cheap way to get the adults is to mix some coca cola with dishwasher soap in an open container and place with the plants. This does nothing to the larvae though

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Cover your medium with a few inches of play sand. The larvae won't be able to get through it to mature and reproduce. End of gnats!

OPU said:

Cover your medium with a few inches of play sand. The larvae won't be able to get through it to mature and reproduce. End of gnats!

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But how am I supposed to use fertilizer (not the liquid one) when there's a layer of sand on top? Any suggestions on that?

SuperKaktus said:

But how am I supposed to use fertilizer (not the liquid one) when there's a layer of sand on top? Any suggestions on that?

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Not sure what kind of fert you're using but you can just water though the sand.

Just buy some mosquito dunks at wal mart and soak them in your water and then water......they contain the Bacillus Thuringiensis that Nullis mentioned

Fungus gnats tell you that you over water. They follow the composting process not poor little roots. What you need to do is figure out how to keep your soil from composting. The answer is usually water way less often. I've had my issues with them and another trick I like is to put 2-sided tape on the rims of my pots. Works like a charm. If you spend 30 minutes applying tape, and forgo watering any of your plants until they look wilted, you'll noticed those flies gone in 7 days my man.

Thank you so much to everyone for all the awesome answers! I really appreciate it, I've never done this before like I said

Apical Bud said:

Fungus gnats tell you that you over water. They follow the composting process not poor little roots. What you need to do is figure out how to keep your soil from composting. The answer is usually water way less often. I've had my issues with them and another trick I like is to put 2-sided tape on the rims of my pots. Works like a charm. If you spend 30 minutes applying tape, and forgo watering any of your plants until they look wilted, you'll noticed those flies gone in 7 days my man.

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This is BS, and you should not (and don't have to) deprive your plants of water because you have fungus gnats. All potting mix contains some kind of organic matter. Decay or organic materials/microbial metabolism is always going on (should always be going on) in soil/potting mix and you shouldn't try to keep it from doing that. Microbes are important for plant roots and plants.

This is correlation versus causation at its best. IF you over water, AND you have fungus gnats it will exacerbate the fungus gnat problem; still having fungus gnats does not = "you're overwatering". Guess what, the plant roots really need moisture too. Microbes that associate with the plants, also need moisture. If you 'solved' your fungus gnat problem by keeping water from your plants, it was at the cost of the plants (e.g. slower growth).

A single adult female fungus gnat can lay over a hundred eggs at a time. With no predators more of them are likely to survive to adulthood and themselves lay eggs. From personal experience I can tell you that underwatering is not an ideal way to "solve" a gnat issue. It isn't likely to help, without depriving the plants of water as well.

All the fungus gnats I have seen will continue laying their eggs in bone dry soil. Their offspring will reduce in number and likely be physically smaller in size. Watering properly and using Bti is more effective and better for the plant long-term though.

SuperKaktus said:

Thanks for your answers, I really appreciate it.

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This solution has yet to be suggested. So the gnats live in the soil and are not inside your plants?
Do you have the money to buy new soil?
Plants are much stronger than many people realize, you can pull them out of the soil and restart. If you think about hydroponics, plants don't even need the soil to survive.

This may take some time and effort but I would try getting rid of all old soil, cleaning everything, including the plants roots, and replant them in fresh soil (your plants are in a controlled indoor environment right?). I would avoid introducing strange bacteria or predators if I could.

I hope I helped.

What do you mean the solution has yet to be suggested?

The solution is Bti/Mosquito Dunks. Other, auxiliary solutions were recommended (yellow traps, gnat gnix). It isn't a "strange bacteria" it is a very good bacteria, from a very common genus as far as bacteria go (Bacillus sp.; e.g. subtilis, pumilus, licheniformis). You know, there can be about 1 billion bacteria in just a teaspoon of healthy soil. Scared of anthrax or something?

I mean, what I am hearing there is essentially "these plants are so much stronger than people realize"..."but you should totally just rip them out over a few pesky fungus gnats". Why avoid treating the soil with something harmless by and large?

Nullis said:

What do you mean the solution has yet to be suggested?

The solution is Bti/Mosquito Dunks. Other, auxiliary solutions were recommended (yellow traps, gnat gnix). It isn't a "strange bacteria" it is a very good bacteria, from a very common genus as far as bacteria go (Bacillus sp.; e.g. subtilis, pumilus, licheniformis). You know, there can be about 1 billion bacteria in just a teaspoon of healthy soil. Scared of anthrax or something?

I mean, what I am hearing there is essentially "these plants are so much stronger than people realize"..."but you should totally just rip them out over a few pesky fungus gnats". Why avoid treating the soil with something harmless by and large?

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he should be glad if they are just gnats, now aphids is a whole other story.

Nullis said:

. IF you over water, AND you have fungus gnats it will exacerbate the fungus gnat problem.

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I couldn't have said it better myself. Since you have fungus gnats, don't overwater or it will exacerbate the fungus gnat problem. You'll have this happen where some people say one thing and some say another. If I were you I'd just try each method on different plants so as to see for yourself which works. For me, if I've had fungus gnats it's meant I've been overwatering, and if I've let them go to wilt it has cleared up the fungus gnat problem.
Drying the soil won't kill the microbe spores. Nullis was right when he said the microbe flora is important to the roots (that is, if your roots have the right microbes to form mycorrhizae, which is the state your roots are in when they're white and fluffy) but most of the microbes in the soil don't help your roots they just compost it. The fungus gnats feed on blooms of these microbes. So if you want the fungus gnats to go away you can't have blooms of composting microbes. Also, taping your rims works really well, but overwatered plants don't grow as well as properly watered plants anyway so why not do it the easy way?
THE solution for the fungus gnat problem is to let the soil drying out. Every time you do the fungus gnat population dwindles almost to zero. You will know the soil has dried out when your plant droops. It doesn't hurt the plant to dry out, but it does hurt the fungus gnat population. If you over water for awhile the population will pop back up again. I hope this clarification helps. Good luck!