Fungus Gnats being a Bitch!!!

I grow with Rockwool cubes as my medium. At this point I have a heavy fungus gnat problem. I've tried Gnatrol and fly strips but I need to get rid of them permanently. I can continue to milk it until after harvest but does anyone have any tips to avoid this problem in the future? This is one of the worst shots and from the looks of it my yield won't be affected but I don't want to smoke the shit.

i recently defeated gnats. you're keeping your medium way too wet on at least one girl--my problem was coming from just one air-pot (soil grow). in addition to really changing how i watered, i utilized yellow stickies, gnatrol, and nematodes...also sprayed CB-80 (great stuff) and covered the one infested air-pot in tanglefeet. won the war.

undercovergrow said:

i recently defeated gnats. you're keeping your medium way too wet on at least one girl--my problem was coming from just one air-pot (soil grow). in addition to really changing how i watered, i utilized yellow stickies, gnatrol, and nematodes...also sprayed CB-80 (great stuff) and covered the one infested air-pot in tanglefeet. won the war.

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Thx for the reply. With a flood and drain style grow like mine my options are limited when it comes to the medium getting too wet. I've minimized the time of the flood cycle to as least as possible. My only other thought was switching to a medium that doesn't retain water as well. Maybe rocks or something.

I posted this here because I figured some of you water guys have had to run into this problem. Any other suggestions.

enfamil said:

Thx for the reply. With a flood and drain style grow like mine my options are limited when it comes to the medium getting too wet. I've minimized the time of the flood cycle to as least as possible. My only other thought was switching to a medium that doesn't retain water as well. Maybe rocks or something.

I posted this here because I figured some of you water guys have had to run into this problem. Any other suggestions.

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sorry-i saw you're in rockwool and i know it's not the same as soil. the CB-80 though is a great spray that knocks out the adults in the air. you definitely need to get them under control. good luck on your quest to defeat the gnats!

stickies, mosquito dunks. At the sacrifice of some trichomes I,m thinking a vacuum cleaning could help.

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I put the sticky strips up, tried scooping most of the gnats out that were walking around my soil, and i added dry soil on top, and then just let my room get a little cold when the lights were off, they died in a few days. They'll randomly come back but when the temp gets a little low, they die. And its not low enough to hurt the plants or anything.

In addition to mosquito dunks, I'd recommend setting out shallow saucers or bowls of soapy water. You'll catch a lot of adults that way. I grow in soil but if your system can tolerate being 'shocked' with a treatment of hydrogen peroxide, that might work. I just pour about an ounce of the food-grade peroxide in a gallon of water and apply it to the medium that the gnat larva are infesting.

Finally, if you can't get all of them, buy a few carnivorous plants like the sundews, butterworts or pitcher plants. Not Venus flytraps because they won't bother to even try to catch something as small as a gnat, usually. That way, you can have the pleasure of watching the little bastards struggle to escape while the plant slowly digests them. Carnivorous plants are a trip, just make sure you start out with the 'beginner' species because some of them are really sensitive to the slightest little variations in environmental factors like humidity, pH, adequate light, temperature (day and night) etc.

crack open a bottle of apple cider vinegar and let it sit out open.... Better yet, put a small amount in a 20oz soda bottle, Poke a couple holes big enough for some straw pieces....


They flock to the scent and can't escape.... Totally great idea....

Thx everyone for the replies. @undercovergrow How did you apply the spray? To the air or directly on the plants or on the medium? @docter I haven't tried the dunks yet because they claim it is essentially the same as gnatrol but I'll try it. Believe it or not I have tried a vacuum...Then I sucked a couple buds right into that fucker. lol @chelcito787 What kind of temps we talking?

@enfamil in flower, i kept the spray aimed toward the containers/dirt and the ground at lights out. FYI do not spray near seedlings. sprayed just a few sprays at lights out and damaged a few leaves on a few babies in veg... they are recovering but i won't use it again (in the veg tent)-no problems with it at all in flower area. i'm still being diligent with watering, etc. seems to be all working together well now.

I like the dunks for the fact they are available anywhere locally I have to pay shipping for gnatrol. Sorry about your fallen soldiers. Good luck.

initially my problem with the gnatrol was i wasn't wetting it sufficiently enough and now that i've adopted better watering habits, i'm really noticing a difference.

Thats good to know.

enfamil said:

Thx everyone for the replies. @undercovergrow How did you apply the spray? To the air or directly on the plants or on the medium? @docter I haven't tried the dunks yet because they claim it is essentially the same as gnatrol but I'll try it. Believe it or not I have tried a vacuum...Then I sucked a couple buds right into that fucker. lol @chelcito787 What kind of temps we talking?

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maybe in the 60's, we had a few cold random days in June at night that ended up killing the gnats. I do it inside but not using the heat and having the AC on got the room pretty cool

Try DE ( Diatomeaous Earth ) - Food Grade and sprinkle over top soil. It is an insect desiccant that will kill the insects , don't dust the leaves because this stuff will stick to the triches. This can be used with other methods described by others.

Budzbuddha said:

Try DE ( Diatomeaous Earth ) - Food Grade and sprinkle over top soil. It is an insect desiccant that will kill the insects , don't dust the leaves because this stuff will stick to the triches. This can be used with other methods described by others.

Click to expand...

Can you use DE in a ebb and flow setup using rockwool?

Is is safe to run a fogger in the veg room? Does anyone think it'll help? I figured after this run I'd clean the shit out of the flower room (as always lol) and use foggers all over the place. I remember what life was like without gnats and I'm just trying to get back to that point without killing everything off and starting over. I'm just nervous because I see the larvae crawling in the rockwool of my new babies and if I don't figure something out soon I'll be they may be worst next time.

The problem with gnatrol or dunks is when the system floods the gnats that were hanging out in the medium fly up to the rim of the pot and crawl around until the medium drains. I would love to place those sticky cards on top of the medium but given how wet it gets I doubt they'll last much more than a day. It seems the best approach will be a multi-headed approach so I'm trying to formulate a good game plan to execute in the next couple of weeks. Once again thx everyone for your replies.

Dude, using a fogger for gnats is like killing gophers with hand grenades. You can do it, but there are a dozen other things to try first.

"The problem with gnatrol or dunks is when the system floods the gnats that were hanging out in the medium fly up to the rim of the pot and crawl around until the medium drains. "

Any gnats that can fly are adults, and they're really more of an annoyance than a serious problem. Which is why you need something that will kill the larvae in your medium before they turn into adults. Mosquito dunks are supposed to do that, and H2O2 will kill the larvae and eggs as well .. just make sure you dilute it enough that it won't harm your plant roots.

There are a couple of organic predator solutions that will work for you. Predatory Nematodes are added to the water from a little tiny sponge. They enter the Gnats in the larva stage and eat them from the inside out. There are also Fungus Gnat Predators too. I've always bought my predators here: http://www.naturescontrol.com/index.html

What's nice about predators is that it's truly an organic solution. The predators eat all the pests and eggs then when they run out of food, die. No toxic man made chemicals are ever needed if you use predators. I love praying mantis! They are just plain cool to have around your yard and make great garden "body guards".

One of my mentors taught me to always let the soil/medium completely dry out between watering. Almost to the point the plant starts wilting. Most pests spend part of the their lives in whatever medium you are using. As long as you give them a warm wet place to grow they will thrive. Let it dry out and the larva die...