Ive got four autoflowers that just sprouted from the soil in 5gal fabric pots. Ive been cooking this soil for three weeks before planting my germinated seeds in a base soil core the size of a red solo cup. I have them under CFL lights until they are strong enough for my QB 260. Today I noticed flying bugs that I assume are gnats. Ive only seem a few, but i want to get on top of things before they breed if they haven't already. My soil contains crab meal which through my research contains chitin a natural pesticide. Is there anything I can do that will help kill/control the gnats without hurting my seedlings and not damage the microbiology of my brand new soil. I plan on picking up some neem meal and top dressing, but how much should I use this early on in the grow. Ive also read about mosquitoe dunks? Will these destroy my soil? Any help/advice is much appreciated.
The dunks are fine, it is an organic larvacide, so it shouldn’t hurt anything but the larva. diatomaceous earth is good as a top dressing and neem oil just a couple sprays to coat the top the soil
Place a layer of sharp sand on the top of the dirt. The sand cuts up the bodies of the gnats as they come out of the soil. I’m organic and that’s what I do.
It does the same thing, it cuts the bodies of the bugs so that they dehydrate and die . Pretty nasty but pretty effective lol
Like enough to cover all the top layer of soil, but do it after ur next watering. Cuz the thing with DE is, it doesn’t work after it gets wet, and it gets a lil messy, it goops up. So I usually let ur soil dry out a bunch to rid some of the gnats then put a mosquito dunk in ur next watering jug the day before you water, then water them, then top dress with the DE. And I would Not use DE when it begins to flower because it blows around to easily and I don’t know how good it would be to smoke fossilized algae, seeing as how it’s autoflowers and your five galllns are probably your finishing pots, I’d see if I can find that. “Sharp sand” stuff maybe it won’t blow around as bad but idk. Either way ull be fine before flower just spray leaves down with water Mist and don’t use it again
Cut out a dry sheet of cardboard that covers the top of your pot with a hole for the stem in the middle. Cut it into 2 pieces with 1/2 the hole on each half. Cover your soil with the cardboard. The gnats will not lay eggs on the dry cardboard.. Remove the cardboard to water. Gnats usually mean your soil is too damp on the top. You can use the cardboard with any of the methods mentioned above. Pop on by my auto thread and say hi. The gang was chatting about gnats yesterday. Cheers Os
Sit a small cup of straight up apple cider vinegar (works better than regular vinegar) On the soil. cover the top in plastic wrap so it is sealed and poke holes in the plastic with a tooth pick or knife. The suckers can’t resist and crawl in and die. I love doing this method because I don’t have to add anything to the soil. They lay eggs in the soil and hatch over time I just sit and wait. works like a charm.
Also in the future, I would suggest waiting for your soil to compost down fully before use. Your patience will be rewarded!
A layer of dry mulch (dry leaves, straw or carboard as @Organic sinse mentioned) and a fan blowing air on top of the soil is all you need to stop them from landing and laying eggs. Actually the fan itself is usally enough to prevent them from landing. I could take an gnat infested pile of compost and clear it of gnats in 24 hours just by training a fan on it so they cant land.
my layer of straw is 3-4" deep. when i water, the straw gets wet but dries out quickly and stays moist below. i think having an extra thick layer of straw helps keep the humidity from the soil less so the gnats don't realize there's moist soil underneath. fan works great! just don't have it on too high if they're still super small. the gnats don't need a strong breeze.
Hi. Just read about the cardboard trick, interesting! Just wondering if the cardboard could be substituted with a layer of TYVEK. It's a moisture barrier which allows air passage. Might work well against the gnats and let air exchange between soil surface and grow room air. Just an idea?