So I’m at a point with my indoor grow that I’m gonna have to use sand to take these fuckers out. I tried sticky strips, watering less, and a little neem oil on the soil surface since all my autos are in flower and I don’t want to spray them with anything. Only reason why I haven’t used sand yet is because I have some top dressings I’d like to do still. My question is, is it cool to top dress on top of the sand? Should I remove the sand first then top dress when needed or shouldn’t the nutrients leach through the sand? Wasn’t looking forward to all the messiness with the sand, but I know it will take care of my problem and I’d rather not have bug buds when I’m done.
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Not even kidding, have you tried something like this?
So if you top dress on top of sand, your just creating new habitat for your fungus gnats. Try spraying your soil with cannacontrol from mammoth p. It’s a mix of corn and thyme oils with a little oleic acid. It’ll put a hurt on them. Or I like dusting perlite with diamataceous earth and using that mix instead of sand, that worked really well for me when I tried it. But if your using soil, fungus gnats are kind of a part of life. I’ve been fighting them for over a decade.
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I use the Mosquito Bits. Works for me. Much easier and less messy than almost anything else.
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It only works for a few months though in my experience, then they seem to become immune. Spinosad is amazing, but not for use during flower
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I topdressed with 2 inches of sand, they still stick around for 1 or 2 weeks, but after that they were all dead. I can probably take out the sand right now, but still didnt.
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That’s interesting, and the first I’ve heard of immunity to the bacterium.
Is it possible that the BTI just needs to be refreshed? I know Mosquito Dunks advertise lasting for about a month. I keep them in the water barrels I water my garden from, and usually add another every few weeks. There is always a gnat or two around if I really look for one, but the MD’s have kept the population too low to worry about for quite a while.
I use gnatrol powder which is just a soluble bti mix. So I mix it whenever I use it
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You’re definitely going to want to scrape the sand away before top dressing. I sprinkled some insect frass on the top layer of my outdoor plants and it worked really well!!
wrap pots in pantyhose and yes the sand on the top. The only thing is they crawl down the stems and in the cracks as the sand dries and seperates from the pot/stalk as well leaves a entry crevice
I use a mix of karanja and neem pellets, this has worked wonderfully, but can’t speak to longevity, have only had it in for a bit over a month.
I’ll look that up - I assume you can also spray the solution as well?
Yep, I buy it on eBay.
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I use a layer of perlite as a barrier.
Needs to be a complete layer, thicker the better.
I cover the holes on the base of the pots too.
Takes a bit of time for them to disappear.
I wash the perlite 1st to remove the fine dust and always wear a mask while working with it.
Once the gnats are gone, I phase the perlite out of use.
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Sand here. Had a lot when I switched to Coco from dwc. Tried neem (hate the smell), tried the yellow stickies…
Sand works great and it’s way cheaper. I just pick up the stuff by the lake! 
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I use what @Seamonkey84 is showing and yellow stickys, the BTi takes care of them fast, the yellow stickys are only there to let me know the gnats are there and how bad
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Appreciate all the help everyone. I’m gonna try Mosquito Bits out first. I’m pretty sure I was overwatering too so I cut my watering in half.
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Gnatrol and yellow sticky traps staked into the pot and hanging in dead zones where your fan insn’t blowing will eliminate these pest. Use the combo and you’ll be good.
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I’m with ya on the Mosquito bits. A grower of 30+ years turned me onto it a year or so ago. Usually one application during pot up and no more gnats again.
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So I gotta fucking tea bag the damn Mosquito Bits
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