How to get rid of a gnat infestation quickly?

master kusher · Jan 17, 2017

I've got a fairly heavy gnat infestation and have been doing what I can to get rid of the lil buggers. (without damaging some of the plants I have flowering) hanging the sticky fly traps from the ceiling but it dosent seem to be working...they get full top to bottom in 5-7 days and I have two in the tent but I need to go pick up another pack, because I only have one hanging. I also recently started putting potatoes in the soil and I saw some dead dried up larvae cling to them but not as many as I thought I was going to see...HELP?! things are getting a little bit crazy lol

MJPassion · Jan 17, 2017

Use 3% hydrogen peroxide mixed 4:1 w H2O for a soil drench.

This will kill some of the adults & a bunch of the larvae turning them into plant food. It will not eliminate the gnats, however.

You may have to do this a few times before you are satisfied.

Also, place the sticky traps, sticky side up, next to or on top of your containers.

You will notice a significant difference in the number of flyers the first day after the drench.

BOMBAYCAT · Jan 17, 2017

I have had pretty good luck using mosquito dunks found at stores like Lowes/Home depot. I crumble 1/4 TSP and place it on the top of the soil and also by the drain holes at the bottom of the flower pot. It is not instant but it takes a couple weeks and no more gnats. The cat likes to chase them, but for me they are a nuisance.

Chevy cHaze · Jan 17, 2017

Hey Master Kusher,
Look for any product that contains "bacillus thuringiensis israelensis" or short BTI and do a watering with it. They're bacteria and will kill off the larvae pretty quick while not harming anything else.I think that stuff might be in mosquito dunks too. Key is to drench the soil with it once and au revoir gnats. works like a charm.
Not sure where you are and what products are available, but it should be easy to find out for you if you do a web search.
all the best,

CC

DemonTrich · Jan 17, 2017

Promis
2ml/gal solo cup clones
10ml/gal up pots

Ru5tyNaiL · Jan 17, 2017

If you have a lot of fliers use a vacuum to suck them up every time you're in your room, and use mosquito dunks to get the larvae.

If you get the dunks, I suggest crumbling them up and putting them in your water for your next watering but you need to let them soak in it atleast a couple hours first. I usually use it in every watering for a few days afterwards to make sure. That usually does it for me.

If you're an organic guy be careful of the h2o2, it will harm your micro herd.

yts farmer · Jan 17, 2017

Use sticky traps and see if you can buy a product called neudomück. Its a german product its very cheap and its is very concentrated so a little goes a long way.

1 small bottle sorry cant remember the correct size but about 50mm can treat 1000 litres of water.

Have a look on amazon and you might get lucky that a seller might stock it.

When i bought mine years ago it cost less than £10 and thats delivery included.

Peace.

Muleskinner · Jan 17, 2017

Assuming you want to stay organic....I use Gnatrol to kill their asses, purchased in 2-pound bags off eBay for $80. A watering of 3-4 teaspoons/gallon of Gnatrol will knock them down by 90% in a couple days and 100% after further waterings.

A great way to kill them all instantly is a soil drench with Neem oil. At somewhere around 1/2 to 1 tablespoon of Neem oil per gallon one watering kills them all. However they will come back over the next couple weeks without further doses and I find that Neem can hurt the plants when used as a soil drench. Some can take it, some can't.

Another quick killer is to cover the top of the soil and the tray under the container in a layer of diatomaceous earth. You have to wait until the top layer of soil has dried out like a crust, the DE will stay dry and they will all get killed. Next time you water the DE gets wet and stops working however, this solution gets messy quickly. It's quite satisfying though, as you spoon the DE powder onto the soil they desperately struggle and flail to get away and die.

moses wellfleet · Jan 17, 2017

Beneficial nematode steinerama feltiae. Problem neutralized!

Within 30 minutes all larvae will come up to the surface and die!

chronosync · Jan 17, 2017

moses wellfleet said:
Beneficial nematode steinerama feltiae. Problem neutralized!

Within 30 minutes all larvae will come up to the surface and die!

(in coco dtw)

yo, while youre here,i am definitely getting some predators but i dont want them to go into a death trap (sm-90, h2o2)

ive been trying to kill them with sm-90 and h2o2 but id rather use BT and nematodes, how long should i wait to apply some nematodes?

honestly i would just flush everything and start clean but my roots cant handle it? im working on some roots but the gnats are making my plants sick and not one of them is giving me the kind of root growth im used to seeing.

not to de-rail a thread but maybe this will help OP too

FireIn.TheSky · Jan 17, 2017

Dunks don't work, they seem to get wise to yellow sticky traps too.

Gotta wipe them out with a soil drench.

brown_thumb · Jan 17, 2017

Liquid BTI worked for me. I just added it to the liquid nutrients when I fed.

chronosync · Jan 17, 2017

FireIn.TheSky said:
Dunks don't work, they seem to get wise to yellow sticky traps too.

Gotta wipe them out with a soil drench.

i watched a gnat land on a yellow sticky today. it struggled, got free, landed back on the card, and of course i watched it struggle as it pulled itself off and flew away....

of course i will still use them, they are catching plenty, but i think im going to ask for a replacement.

moses wellfleet · Jan 17, 2017

chronosync said:
(in coco dtw)

yo, while youre here,i am definitely getting some predators but i dont want them to go into a death trap (sm-90, h2o2)

ive been trying to kill them with sm-90 and h2o2 but id rather use BT and nematodes, how long should i wait to apply some nematodes?

honestly i would just flush everything and start clean but my roots cant handle it? im working on some roots but the gnats are making my plants sick and not one of them is giving me the kind of root growth im used to seeing.

not to de-rail a thread but maybe this will help OP too

If you can't flush I am guessing you could use the nematodes after a couple days. First prize would be to ask the supplier.

Btw I never saw results from BTi. But I really recommend those nematodes. Follow directions exactly! Good luck!

MJPassion · Jan 19, 2017

I've never had good luck with bti either.
It works but it does not eliminate gnats.

The only time I've ever seen gnats completely disappear is with a H2O2 soil drench followed by nematodes... Even then, it only lasted a few months.

Dog Star · Jan 19, 2017

You give them "cinnamon challenge" but literaly...

surface of your soil top dust and sprinkle with a cinnamon before watering,then water..
and later enjoy whithouth any larvae inside soil..

off course stays those that fly but for them sticky straps is best..

RB56 · Jan 19, 2017

I never had luck with nematodes. BTI works (I used Gnatrol) but you have to do 2 or 3 drenches, a few days apart. Literally smells like shit.

You have to understand their life cycle. They only live for a week, but you have eggs, larvae and fliers. Nematodes and BTI only kill larvae. That leaves fliers laying eggs in the medium and existing eggs hatching.

I had infestations every spring and summer for the first few years I was growing indoors. I've completely eliminated the problem by preventing them from moving between air and medium. Here's what I do:
https://www.icmag.com/ic/showthread.php?t=290400
Started in soil but switched to coir a few years ago and it works just as well. I reuse the screens and pea gravel so there's very little ongoing cost and effort. Also prevents washouts during watering.

brown_thumb · Jan 19, 2017

BTI killed my fungus gnats after a few drenches but I still have some other kind of really tiny gnats that BTI and neem oil have little or no affect on. I think I'll tie a layer of pantyhose over the top of the soil as a barrier.

Sativan · Jan 23, 2017

Find some Microbelift BMC. It works wonders. After about 2 weeks you'll find you have your plant back to yourself. I had a large infestation and hit them with Microbelift and I haven't had a problem in six months.

Jhhnn · Jan 23, 2017

It's near impossible to eliminate gnats entirely, I think, but they're easy to control with Microbelift BMC or Gnatrol. I just follow the instructions w/ gnatrol- drench the medium w/ 1 tbsp/gal once a week for 3 weeks. Even a single application beats 'em down to almost nothing. Good shit, Maynard.

I use fly ribbons as an indicator. When I see more than a few stuck gnats it's time to dose the plants. Don't wait because the population can explode quickly. Low populations are merely a nuisance but high populations can cause root damage & open the plants up to fungus & bacteria.

How to get rid of a gnat infestation quickly?

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