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Old 10-06-2016, 06:14 PM
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Join Date: Jan 2016
Posts: 328
Default How can I get rid of fungus gnats?

It's been an extremely rainy summer and fungus gnats are thick outside and have found thier way into medium.
Each time I feed I see 4-10 per container coming up out of sides where medium meets sides of containers.
I'm at the end of week 7 and they're not up on leaves or in colas,I keep air moving at all times and hopefully this helps keep them at a minimum.
I've read they are more of a nuisance than harm causes but bugs can attract bugs.
I've read to use dish soap and water folarly,neem oil,hydrogen peroxide,but it's my first pest problem and with harvest just around the corner I don't want to cause more damage or spray colas with something that won't wash back out.

What can I use and how do I apply it and wash it off if I spray colas?So far colas and plant look uneffected and evert gnat I've seen is either on or around medium.
Also,could I be over watering in coco?
I'll get a few house flies but this year it's rained so much the ground outside has never dried and it's a bugs paridise.

Last edited by Indi; 10-06-2016 at 06:21 PM.
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Old 11-05-2016, 04:29 AM
Join Date: Jul 2013
Posts: 39

Put an inch or so of the corsest sand you can buy on the top of each pot. You may need to put a saucer down, so when you water, the stream doesn't drill through it! The adults can't lay if the substrata is dry! Sand is dry, so when the current larvae hatch into flies, they ll disappear. Easy. Combined with a drench, it ll be fixed in days!
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Old 11-05-2016, 02:17 PM
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Join Date: Nov 2015
Posts: 922

What craig said works.

I personally just removed all infested soil from my space and let it completely dry out or just threw it away (the cheap garden soil which caused the infestation I threw away, the good supersoil I made myself I let dry out in a separate room for the duration).

What craig said is the solution if you don't want to do what I did.

What I would add:
Yellow strips to catch the grown up "flyers". This way you also thin out the existing grown up gnat population and there are less attempts to lay eggs.

Worked quick for me. After hanging the strips and getting rid of the shitty soil, I would say 2 days or so and I had no visible flyers anymore.
The odd one appears here or there even weeks after now but I am talking 1 or 2 flyers and no soil for them to infest. I think they come from the compost pile of cut down males
But that stuff is also so dry now, I doubt any more will show up.

I hang yellow strips in all chambers now just to be safe and catch the odd critter.
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Old 11-05-2016, 02:48 PM
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Join Date: Jan 2016
Posts: 328

I am using organic dia earth something,it's a very fine sand,and BTI bird bath strength.
I'll take a look at corset sand also.
The larva were thick enough that their waste started effecting drainage or just root damage.

I just know I don't want them again and used medium will get thrown in garden and winter should kill the grubs.

Hydro shop said to use BTI for a whole cycle and sticky traps for adults.

Thanks for replies.
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Old 01-19-2017, 04:15 PM
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Join Date: Nov 2016
Posts: 3

i have found that the mosquito dunks work very well... if you put one in a larger reservoir of water, like a 50 gal tank, and then use that water to irrigate your pots/plants, it will usually clear up the gnats in a month or so. it is an all organic product and the active ingredient is : Bacillus thuringiensis israelensis

some people say that the granulated product that they make is better for a top dress, but if you read the label you will see that the dunks have a much higher concentration of Bacillus thuringiensis israelensis....
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Old 01-20-2017, 01:56 PM
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Join Date: Nov 2015
Posts: 922

I might have spoken too soon.

I have bascially been watering with BTI for more than a month now and even though I felt like it was working, I recently popped another small batch of seeds and the high humidity in the propagator seems to have caused an explosion of gnats ...

There were so many again.

I continued watering and letting them dry out considerably and also top-dressed with diatom. earth.

It doesn't seem to get rid of them, just to control their numbers.

I have very few flyers now but when I water after letting them dry out and applying diatom. earth, there's immediately a hand full of flyers in the air again.

I will probably just finish this grow and then scrap everything, clean with bleach/chlorine everywhere, let the soil dry out 100% and begin fresh.

Let's see if I can save a clone or two so I get a head start after the reset.

But having battled these gnats for more than 2 months now, I am not willing to continue and just "control their numbers". I want to get rid of these bastards for good before I continue.
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Old 01-20-2017, 06:54 PM
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Join Date: Feb 2013
Posts: 114

For potted plants mosquito bits works really well. Plus it's easy to use sprinkle some on top of the soil and as you water it works!
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Old 01-24-2017, 04:20 AM
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Join Date: Jan 2016
Posts: 328

I'll have to try mosquito bits.

BTI bird bathe was ineffective maybe because cultures were expired.
Azmax did seem to help .
Spraying with dog flea and tick shampoo worked fast and highly noticeable.It has phenothrin in it which is made from flowers and used on many edible crops by dust croppers.

I had swarms above medium at all times and after just one application of phenothrin they were gone for 4-5 days.
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Old 01-24-2017, 05:55 AM
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Join Date: Jun 2014
Location: Great Southern Land
Posts: 680

Im grateful that I have never had to wage battle with these little buggers. My organic friends use a thick layer of insect frass and then place a layer of gnat nicks (sp?) As the insect frass breaks down an enzyme called chitonese is produced which in turn breaks down the shell of then eggs laid by the gnats. Gnat nicks is fine ground recycled glass that works as a dry layer that literally cuts up any gnats trying to get to the moist layer to lay eggs. Then with the addition of predator nematodes in the media which eat the larvae that do hatch. Apparently this works well in combination with sticky traps so that you are then targeting each of the gnats stages of life. A bit if googling should yield you suppliers of each of these products.
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Old 01-24-2017, 06:29 AM
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Join Date: Dec 2010
Posts: 727

Would wrapping the pots with a mosquito net help?
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