Fungus Gnats

[JohninWI]

I'm having a bit of a problem with fungus gnats.

I'm growing in a home-brew soil mix. It's about 50% peat, 10% vermiculite (really coarse--about 1/2" pieces), 5% perlite, and mushroom compost and local "landscaping compost".

I supplimented it with blood meal, bone meal, Chickety DooDoo (love that stuff!), some epsom salt and some agricultural lime.

The runoff pH has been stable at about 6.6. Nice green growth--plants seem to be happy and healthy. Temps are a little on the cold side (in my basement in WI!), and swing from about 72F in the day time to maybe 60F at night.

My problem is that I live away from the room all week, and only can tend to it on the weekends. So to help with water stress, I've had luck using "water crystals" as prescribed on the package. That limps them through so that they have not yet wilted after 5 days under my 400W HPS.

I'm wondering how people have succeeded in getting rid of fungus gnats? I've searched and searched, and everyone contradicts everyone else. Some say drench in Neem, some say it kills your plants. Some say nicotine is the best way to kill the larvae, some say hydrogen peroxide...

The plants are about 10 days away from going to 12-12, so I guess it would be ok if I used something aggressive--it should be flushed out by the end of flowering.

What do you think about this for a treatment plan. I could use the hydrogen peroxide soil drench (they are saying 3 parts 3% H2O2:5 parts water) to hopefully knock the larvae back. Then 2 days later, use a nicotine soil drench to take care of the rest. Maybe treat again in a week or two. That should take care of at least 1 entire life cycle of the gnats.

I don't think that over watering is causing the problem--not by watering every 5 days, when the pots are really getting light. So I'm wondering if the water crystals are causing this? Or if maybe I innoculated the whole deal by using mushroom compost? Whatever the deal is, I want them dead!

I'd be willing to buy a product, but only if it's going to work.

 

[4u2sm0ke]

Dieotsearth(sp) mix this into top 1 inch of your soil..bottom feed for the next couple weeks End knat issue DEAD!!!...and can be used upto Harvest...only issues ive seen is watering from top and useing too much dieos..the adult knats are not the issue..its the larvae feeding off the roots..your plants seem to grow slower when ya have this issue?...kill them buggies..Hope this helps..


take care and be safe:bolt::bong:

 

[cmd420]

Dieotsearth(sp) mix this into top 1 inch of your soil..bottom feed for the next couple weeks End knat issue DEAD!!!...and can be used upto Harvest...only issues ive seen is watering from top and useing too much dieos..the adult knats are not the issue..its the larvae feeding off the roots..your plants seem to grow slower when ya have this issue?...kill them buggies..Hope this helps..


take care and be safe:bolt::bong:

exactly.. if you're in soil, they're easier to get rid of..

the "diamataceous earth" (google it) that 4U was talking about is what you need..

on a microscopic level it is glass and cuts them to shreds when they try to walk on it..

yay

 

[trillions of atoms]

yup...DE IS THE C H I T! .....till the soil with a fork to help aerate and kill the larvae. the oxygen drys the babies up before they can hatch.

 

[JohninWI]

I don't mean to doubt anyone--but have you guys used DE? I was about 1 click from buying some off of HTG supply last night, but there was a lot of conflicting info on google about it.

I know they do use it for long-term storage of food and animal feed. It slices the little critters and bugs to pieces--they just sprinkle a little and mix it in with the soil. But as long as you don't get it in your lungs, it's ok for mammals.

I'd be all for giving it a try. I got to get this taken care of before they really start chewing up my roots!

 

[4u2sm0ke]

I use it religously my friend...I use to fight those turds and was told of DE by Hick here a few years back. and have used ever since..its also organic so that was a plus for me...we not telling ya to smoke the stuff..lol...sprinkle it and turn into your soil...just remember not to water from top for a few feedings and you will be fine...Now why would ya wanna google something you have better info from a MJ site..perferably this one...I realy dont know of many peeps here that would stear ya wrong..well not without the folks here chiming in...now go get some DE and Kill those Bastards:hitchair:

take care and be safe:bolt::bong:

 

[ArtVandolay]

I use it, too :hubba: I also hang sticky tape fly catcher things to catch the flying stuff :hubba:

 

[mojavemama]

I'm so glad you posted about this. I have been battling them for a year, and yes, they do stunt the growth tremendously. I was shocked to see how FEW roots my plants had after I harvested them. These are nasty little buggers. I'm going to get some DE now. I have read about it, but because it's so dry here in the desert, felt it would not be good to inhale for us or the animals. But now, I've clearly lost the battle. I'm going DE. Thanks for the great info!

 

[JohninWI]

Excellent information guys! I've never had to deal with these little beasties before.

I have a hilarious story from today. I work at the University (as a chemist), and made friends with a botanist--crazy old hippy chick. We've never "talked" about anything, but I'm sure she's cool (you just kind of know. stone-ar!).

Anyway, today I said I was having "some kind of insects coming out of the soil in my houseplants".

Without missing a beat she said "Oh, I had fungus gnats when I used to grow pot in college--go steal some Celite from your lab and rake it in".

So I googled it--Celite (this filtering medium we use) is actually just diatoms that are carefully cleaned (and way over priced).

So there you have it folks--I got the ok from a real PhD botanist!!

Anyway, are the chances for recovery good, if I can kill those little son's of boomers?? At the moment, the plants look healthy, so I hope I can treat them for the gnats, and maybe veg an extra week to hopefully repair some of the damage.

Thanks again--man, this whole thing has been a real drag. My DE is on the way, should be in by Thurs.

 

[mojavemama]

Great story, John! Can't believe none of the nurseries or hydro shops here carry it. There is only one place in our state that does--an animal feed store. So at least I don't have to pay for shipping. Getting some tonight.

 

[mojavemama]

John--I never saw any damage. My plants looked healthy, they just were stunted, much smaller than they normally are, so really reduced yield. The real damage wasn't seen until I harvested them and emptied the pots. The I saw how short the roots were, how they never filled out. My 5 gallon pots had plants with a root system of those in a 5" pot. Seriously.

 

[JohninWI]

YIKES! Well Mama, hope the folks over here gave us the magic bullet for treating them. So far I haven't noticed any delayed growth or signs of injury--maybe I'll get lucky and catch it before anything goes REALLY wrong.

Good luck on your end.

 

[4u2sm0ke]

I use it, too :hubba: I also hang sticky tape fly catcher things to catch the flying stuff :hubba:

I tried those and kept walking into them in SHed:doh:...I read they attracted to the color yellow too....Maybe get a bright yellow bowl from dollar store...maybe spray some addhisive inside ..lol...Im stoned never mind

take care and be safe :bolt::bong:

 

[mr. b]

well i too battled the little turds for years, until i got mosquito dunks threw one in water crushed it up the next day and poured the mixture in my soil tote and mixed it in, i have now been about 6 months without seeing one again, (this is the longest i ever went without) now every time i bring in new soil i just do the same before using it, as i was getting them every time i brought in new soil, i used the de on the existing plants and all the new ones have the dunks, i found that info on another site and posted it before. but after our web troubles i have to start over again

 

[mojavemama]

4U, I can't help but laugh about the yellow mosquito stickies. Oh, man, they are DEADLY around me, with the powerchair. I run over them, pull them off the tires, and there is still enough sticky left on the tires that I roll through the house picking up dirt and dog hair like you'd roll a snowman. That stuff is HORRIBLE! And every time I moved a plant, I'd lose leaves from the stuff catching on the leaves. When I got stuck on a bud, I decided to throw that stuff out and never use it again. It requires someone with a bigger brain than mine to use it.

 

[mojavemama]

Mr. B, glad to know the mosquito dunks worked for you! I grow organically, so I don't use pesticides, but man, if you got rid of them, I'm thrilled for you. Nasty little buggers. Now, this picture should make you sick: it's of my root system on my last grow. They were all in 5 gallon pots. What you see is what's left of the roots when I unpotted them. Sickening, isn't it?

View attachment FungusGnatDamage.jpg

 

[JohninWI]

Actually, most of the mosquito dunks are made from bacteria (Bacillus thuringiensis israelensis) that kill the mosquito in it's larvae stage. hxxp://www.epa.gov/pesticides/health/mosquitoes/larvicides4mosquitoes.htm

I don't know if it qualifies as "organic"--but it doesn't contain synthetic pesticides.

I'm guessing that the bacteria kills the fungus gnats in there larvae stage too? I think with mosquitos, the bacteria bores in there and soaks up the larvae juice for food.

Yum-nice larvea juice.

 

[mojavemama]

John, that's handy info to know! Thanks so much.

 

[gchristo]

Mosquito dunks worked for me as well. I grow drip in rockwool, and fungus gnats wrecked havoc on a WhiteWidow grow last year. Threw one dunk into my resouvoir and in short order the gnats were gone. However they could cause a problem. As they slowly dissolve they break up and create a mess in your res. If I ever need them again, I will place the dunk into a fine mesh bag to capture all of the floating bits of the dunk that make for an unsightly res container. Just a little bit of extra cleanup when you must do necessary maintenence, but be aware of the potential for a pump clog, or a drip or mister clog.
Cheers.