I’ve battled gnats a few times in my grows, currently have them on run at the moment. Fingers crossed!
I’ve used a few things to keep them in check, but I don’t think I’ve ever got rid of them completely.
I’ve added Hypoaspis Miles, they work great on the lava, nematodes (watered in with a watering can rose, as a pressure spray will smash them around too much and kill a lot of them).
Then there’s Neem oil, which works well as a deterrent. Ive used gnatrol with mixed results too,
And the last thing I’ve tried was a dry down of the top soil. I hadn’t intentionally done this, but I was away at hospital and meant I didn’t water for like 6 days. That seemed to kill off a load of them. But it’s not ideal for living soil as it’ll also kill off a lot of the biology in that top layer… it’ll come back again though.
Ive dealt with gnats constantly for at least 20 some odd years and at times I can get some really tough to deal with infestations. It would take too long to expand on every approach that I’ve taken to combat them but in my experience :
The gnats that I get are not affected at all by neem and actually seem to enjoy it.
Diotemaceous earth does nothing other than pose a health risk to the person applying it.
Drying out pots will kill the plants way before it ever kills gnats. These are in 1 GAL pots keep in mind. In a 20 gal pot where you can allow the top few inches to dry out for some time it would be different.
Predatory mites are good at controlling the larvae I agree. In high quality compost they often times show up naturally as well. I’m not using high quality compost. To be most effective I feel you need to use a combination of mites + nematodes , bt or something else.
Nematodes are great but sadly I just checked today and my local garden center that has them confirmed they are 6+ weeks old. Don’t really want to waste money gambling on viability. Also don’t want to pay for shipping in the middle of summer on nematodes either so I may skip nematodes this time.
Bottom watering is a semi viable strategy but I still get gnats in the bottom of the pots / holes. Also don’t really want the feeder roots to completely die out.
Just got home and rushed into shower so I can check on the plants, going to have to cull a few males and will update again.
I hope my posts don’t come across as dismissive or know it all, I’ve just been down this road with gnats so many times and a lot of the conventional wisdom doesn’t line up with reality from what I’ve observed in my climate. Nearly every suggestion for gnats I have encountered but still appreciate the posts just in case it happens to be something I haven’t seen or considered. Love the yellow folder idea for the tanglefoot…
It’s all good! Don’t worry about it, I knew when I shared my attempts at taming the gnats, that you’d have likely tried them all already at some point.
Just thought I’d chip in, as I’m constantly battling them too
Me too! Haha. I read it on IC I think? Read it a few years ago when supplies were scarce, been tryin to repeat it as often as possible ever since. For the cost of 2 packs of sticky cards, you can make dozens of plastic folder ones. And as you already know, tanglefoot is boss. In times of desperation, I paint it on the rims and bottom couple inches of pots, and the rims of saucers. If it gets real bad the pots looks velvety from all the flies stuck to them. And when you forget and grab a pot from a sticky spot, that’s pretty gross too. But it works!
There are many days when the area is in the mid 90s which to me still doesn’t sound ideal. Plus the container it was in is transluscent and not the tightest seal on the lid (cheap plastic folgers coffee can)
I can only assume this applies to Gnatrol as well. I think it’s just my crappy storage of it, plus I’ve had it for over a year. I assume my “main supply” of it will be more effective. At least I hope haha.
Why not just store it in the fridge? I mean, if “extreme cold and even freezing temperatures will not reduce the effectiveness,” seems like the fridge would be a good place to keep it. I might even move my Gnatrol into the seed fridge after reading that.
Just being lazy or doing what’s convenient. Often times I have to rush in there before / after work to water and I like having the gnatrol close by. My larger supply of gnatrol was kept in fridge-like conditions and am going to start using that now. May change my practices too, probably not… Will probably just keep a smaller supply of gnatrol in there (1 month rather than 1 year…)
Here’s a blurry old phone shot of the tent SSDD bottom left , C next to it, everything else A:
They thrive in moist conditions, especially in the presence of decaying organic matter. The medium doesn’t have to be over-watered or waterlogged though. Over-watering creates an even more hospitable environment for them for sure. Occasionally I do have to correctively water to runoff in the saucer when I go in there, they are wilting, and I’m going to be gone the whole day. By the next time I go in there the pots are bone dry and very light. I’m probably going to have to water a couple of the pots sometime tomorrow, it is what it is.
I don’t want to open up a can of worms with shifting to moisture requirements in organics, pot size, or any of that really. I like growing in water-only organic soil-less mixes and in small pots. Am all ears if there is a good watering solution for my current style ( many 1 GAL pots, water only). I kind of just half-ass it and usually rely on BT / nematodes / mites to prevent outbreaks, but this time I got caught slipping with the gnatrol.
The issue in my mind was created by topdressing with a low quality store bought worm casting and relying on gnatrol that was stored improperly.
It’s highly probable that that’s the reason this time, but it just seems like fungus gnats are always gonna be an issue, most of the time haha, to varying degrees, no matter what you do.
I will say that I quit top dressing the seven-gallon pots with EWC/Bu’s Blend a while back because that was a guaranteed hardcore infestation (still use it in my soil mix, though). Which is weird, because I didn’t have a problem with gnats for the first few years of growing, even though I always top dressed with either the EWC or the Bu’s. They just appeared one day. And I still always see a few gnats around no matter what, but if I water with Gnatrol within a couple days of the first few showing up, they go away, usually only takes one watering as long as I do it before shit gets out of hand.
Right but a few fungus gnats staggering around is easier to handle before it snowballs into an outright infestation. I agree with you though, BT tends to be effective at putting an end to future generations. I feel like this go around BT was not effective because of the way that I foolishly stored it. Just because I do things the way I do them doesn’t mean I think it’s the best way, there’s compromises everywhere. I also think if I just had 1-2 inches of straw the gnats would not be as severe. I was worried about the TS not having enough root space by mid-late flower and impulsively went with worm castings.
I was helping my friend make adjustments to his non-cannabis greenhouse in 2010~ and remember taking down a bunch of bug zappers that were hanging. I know he wasn’t thrilled with them and now relies on predatory mites almost exclusively, nematodes would be his next choice. They never got rehung or replaced.
Don’t think I’ve ever tried them in one of my tents, definitely not in a flower tent and not within the past 15~ years. Seems at best it’s like a more attractive sticky trap. I’m not sure fungus gnats are even attracted to the UV light in them and even though it’s probably safe I still probably wouldn’t feel comfortable having a UV light on in the tent during the dark cycle. Been a while since I’ve read up on crytpochrome or phytochrome, but I’m more thinking about just the general stress being a potential trigger for intersex issues rather than being a light-cycle interrupter.
Have you used a bug zapper in a flower tent before? If so what are your thoughts on it?
I have not. I have thought about it though. Could probably run it for 10-15 mins as soon as the lights go out and be fine. That way the light cycle isn’t messed with too bad. Might help make more trichomes too.
Possibly. I mulch with straw every grow and the fungus gnats still show up (briefly). The worst infestation I ever had was the one grow when I switched from barley straw to composted bark mulch, but I dunno if that had anything to do with the type of mulch I used that grow.
I actually haven’t had an issue with gnats during this current grow, didn’t wanna mention it because I don’t wanna jinx myself haha. I saw a few when I was vegging in the half-gallons, watered with Gnatrol and the OG Biowar Foliar pack and they disappeared. Pretty surprising, really, because I usually have to water with BT at least once after I’ve transplanted into the seven-gallons.
I did put one little scrap of a yellow sticky trap in each seven-gallon pot, just as a sorta preventative, and there’s a few bugs stuck to some of them. They don’t look like fungus gnats, though. I dunno what they are. And that’s actually making me kind of nervous haha.
Would you hang it? Or would you somehow place it near the soil line or tops of the pots or whatever? Because fungus gnats don’t really fly super-high, they seem to kind of stay around the soil, except for the occasional random gnat or two. Hanging it seems like it would be kind of pointless; keeping it near the tops of the pots, almost ground-level, sounds a little dangerous.
To my mind it would have to be at the soil level. I don’t want to attract gnats into the canopy level where they can get stuck on more buds on the way, or have them die and fall into the buds haha. A gnat stuck to a trichome is still a gnat stuck to a trichome no matter how it died.
Ahh, OK I didn’t even consider there are plugin bugzappers. I’ve only remember seeing the battery ones that hang. Now that I think about it I think the greenhouse ones did have wires attached to them… Not sure though. I’d probably buy one for outside the tent if I had more space for the floor area, already a pretty tight squeeze though. Seems like it could be a cool layer of defense actually.
Also about to take my dogs for an adventure but am going to make up some sticky traps with tanglefoot when I get home… No more procrastination… I already have the pieces made!
I agree, although you’d probably need more than one zapper, even at ground level. I feel like it’d only be effective for the portions of the pots that it was closest to, so having several spaced around both the “insides” of the pots and the “outsides” of the pots, relative to where they are in your tent, would be the most efficient use of them.
This sounds like it’s getting spendy haha, although I really have no idea how much those zappers cost, haven’t even seen one of those since I moved away from Florida like 27 years ago haha.
Bust out the traps and water with some BT, I’m sure they’ll go away.
I have a bug zapper bulb 4 or 5$. I havent tried it out yet but if it does work. They would easier to hang one in the upper corner and one under canopy in opposite corner than the larger units.
