fungus gnats

i put a layer of sand on top of my pots cause i read it will stop fungus gnats. how long until i can get rid of the layers of sand? how long is the entire life cycle for the fungus gnats. i read something like they cant lay eggs in the sand or the larva cant reach the surface or something like that. how long do i have to wait?

I cannot help with that but assume at least it stays on for equiv of a few gens of the buggers? but suspect that many would simply leave it in for duration rather than take the time to try and scoop it all out again!? I wrote cause I think I am having similar issue but am having a hard time confirming its a gnat issue- any chance you have pictures of the damage or symptoms they leave behind?

I never tried that method, I know you need to kill the larvae in the soil also, I read the best method is too soak some tobacco in water for a few hours strain all the tobacco out and pour the water over the sand the nicotine will kill the larvae in the soil.

I never tried this method I found a bunch of sticky fly paper to do the trick.

Sterilise your soil in an oven before planting.

skiweeds said:

i put a layer of sand on top of my pots cause i read it will stop fungus gnats. how long until i can get rid of the layers of sand? how long is the entire life cycle for the fungus gnats. i read something like they cant lay eggs in the sand or the larva cant reach the surface or something like that. how long do i have to wait?

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I don't think you ever get rid of the sand. Your supposed to remove the first 2 inches of soil then replace with sand.... Fungus gnats are a bitch to get rid of..

The adults live about 3 days. I can't remember exactly how long the 'egg-larvae-adult' phase takes, but I think it's about a week. At any rate, if you wait close to 3 weeks, then scoop out most of it, by hand, you should be good to go. It doesn't take that much sand to deter them from laying eggs, so as long as you leave a thin layer of sand(like 1/8"), on top of the soil, afterwards, they shouldn't be back. Also, it doesn't take that much sand in the beginning, either. Go with just enough so that the soil isn't visible, and that'll do. Add much more than that, it the sand starts to become a watering nightmare, as you might've noticed.lol

I've used it once, in the Spring, and it worked great. Haven't seen one since.

jawbrodt said:

The adults live about 3 days. I can't remember exactly how long the 'egg-larvae-adult' phase takes, but I think it's about a week. At any rate, if you wait close to 3 weeks, then scoop out most of it, by hand, you should be good to go. It doesn't take that much sand to deter them from laying eggs, so as long as you leave a thin layer of sand(like 1/8"), on top of the soil, afterwards, they shouldn't be back. Also, it doesn't take that much sand in the beginning, either. Go with just enough so that the soil isn't visible, and that'll do. Add much more than that, it the sand starts to become a watering nightmare, as you might've noticed.lol

I've used it once, in the Spring, and it worked great. Haven't seen one since.

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Yeah no doubt, you have to water from the bottom up thru drain holes if you put too much sand in..

303 said:

Yeah no doubt, you have to water from the bottom up thru drain holes if you put too much sand in..

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Exactly, and that's asking for trouble, IMO. When I used sand, I ended up scooping most of it back ouit, the first time I had to water them. I started with about an inch, left about 1/4", then mixed it into the top layer of soil. It was still a bitch watering, though. I had to add water, wait 10 minutes or so, for it to soak, stir around the soil, then finish watering. I was glad to see those little bastards gone, lemme tell ya.lol

jaydag71 said:

I cannot help with that but assume at least it stays on for equiv of a few gens of the buggers? but suspect that many would simply leave it in for duration rather than take the time to try and scoop it all out again!? I wrote cause I think I am having similar issue but am having a hard time confirming its a gnat issue- any chance you have pictures of the damage or symptoms they leave behind?

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they are not causing any visable damage. but i've had them for a while, been using neem for about 2 months and its not stopping them. im afraid to make the neem too strong cause i dont want it to damage the roots or coat them to the point where it blocks water intake. i also have fly paper all over, it does help. i did find one good thing with the neem though, i no longer have that thin layer of fungus on top of my soil which is probably what they liked to eat. besides the gnats i also have their larva all over in the soil. those little white worms. then also the pupa, they look like mites but they're really just baby fungus gnats. i know they're not spider mites. already had that problem and took care of them. damn was that a bitch. even though the fungus gnats are not causing any visible problems and my plants are doing fucking great, i still want any visible bugs in my soil dead.

Spanishfly said:

Sterilise your soil in an oven before planting.

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i use fox farm ocean forest and they dont recommend that. this quote is taken from their website
"Are your soils sterilized?
No, we don’t sterilize our soils because that would kill the very beneficial microbes which are critical in making nutrients available to plants. Your soil should be alive, not sterile! Our mixes contain beneficial fungi and micro-organisms that help plants become more disease resistant and grow healthy root systems. FoxFarm soils and fertilizers are specially formulated to build massive microbe populations."
although im sure a lot of those beneficial microbes and especially fungi are dead from all the neem since neem is an excellent fungicide. but at the same time, im sure my fox farm big bloom replaces a lot of the microbes.

thanks everyone for the info. i will rep u all.

I started to see them flying around the room. I never saw any larva in the soil. I covered the top of my soil about 1/2" for a week. I did not water unless the plant was wilting. They never did. After a week I dumped the sand out and watered as usual. Try to increase your fresh air and lots of air movement to help dry out the soil. Do not overwater. I haven't had a problem since. I was using molasses at the time and that's when I started to see them. I will start molasses again soon and may find they come back? I have heard of some using H2o2 to kil the larva but that will also kill all beneficial bacteria so its not recommended.

venacular said:

I started to see them flying around the room. I never saw any larva in the soil. I covered the top of my soil about 1/2" for a week. I did not water unless the plant was wilting. They never did. After a week I dumped the sand out and watered as usual. Try to increase your fresh air and lots of air movement to help dry out the soil. Do not overwater. I haven't had a problem since. I was using molasses at the time and that's when I started to see them. I will start molasses again soon and may find they come back? I have heard of some using H2o2 to kil the larva but that will also kill all beneficial bacteria so its not recommended.

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thanks. yeah before i made the noob mistake of overwatering. i sterilized with scalding hot water some sand from a lake michigan beach. it's been on the surface of the plants for about 3 days now. the layer is about 1/4 to 1/2 inch thick. i will keep posted on how everything is going. i use fox farm's; ocean forest potting soil, grow big, tiger bloom, and big bloom. advanced nutrient's overdrive. also schultz neem oil extract. thanks again everyone for the info

Spanishfly said:

Sterilise your soil in an oven before planting.

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No need to.

303 said:

I don't think you ever get rid of the sand. Your supposed to remove the first 2 inches of soil then replace with sand.... Fungus gnats are a bitch to get rid of..

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skiweeds said:

i put a layer of sand on top of my pots cause i read it will stop fungus gnats. how long until i can get rid of the layers of sand? how long is the entire life cycle for the fungus gnats. i read something like they cant lay eggs in the sand or the larva cant reach the surface or something like that. how long do i have to wait?

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First, you don't use regular sand. You go to home depot or whatever, and use landscaping sand..this is the stuff that you sweep in between the cracks when you're laying pavers (bricks). You don't need to remove any soil, but you do apply it AFTER you water, so that the moisture gets absorbed by the sand, and make sure there's no soil visible on the top. When it drys, it will get hard and prevent them from laying their eggs...the only thing is, they like to sometimes hide just inside the container on the bottom where the drainage holes are, especially if you have side holes.

But it does work and I do it from time to time, and you can easily remove the hardened sand the next time you water, and if you want, reapply it again, but usually after two treatments you've got 'em. gl

I didnt read the whole thread so i dont know if this was already said but this is what i did and it worked like a charm.

covered all the pots wit an inch or two of playsand from home depot to kill the larvae and put up HOT SHOTS NO PEST STRIPS to kill the flying adults.

hot shots pest strip link----------> http://www.google.com/products/catalog?client=safari&q=hot+shot+pest+strips&oe=UTF-8&cid=4393286466863082832&ei=k3C_TPIrpbiLBNOAzdkD&sa=image&ved=0CAgQ8gIwADgA#p

Worked like a charm and still dont have any gnats

Hope i helped

Punk said:

First, you don't use regular sand. You go to home depot or whatever, and use landscaping sand..this is the stuff that you sweep in between the cracks when you're laying pavers (bricks).

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is there really much of a difference? the sand from the lake michigan beach i went to is real fine. barely any other bullshit in it at least at a macroscopic level. im sure its not as pure but thats why i rinsed it all real good with scalding hot water before putting in the pots. the house i grow at doesnt have a scold guard for the faucets so it's almost like boiling hot water coming out(shhh dont tell the building inspectors, it's against code). i made sure no soil was on top. im probably gonna have to water in a few days so i think i'll just take it out and reapply it. probably best to have it on there at least a week or 2. im also still spraying neem oil on the surface of the sand. thanks, i reped everyone that i havent yet.

yea i dont know i get the play sand from home depot cause its rinsed and sifted. if you got to the beach for sand you risk bringing in more bugs that will probably fuck shit up worse. but its up to you. But home depot sand that im talkin bout is like 5 bucks so it up to you

i spray about once a month with azamax and i spray the dirt is that ok? i dont have a gnat problem now but at what cost to my golden nuggets?

a larviecide will help end the cycle but they can get in the holes on the bottom of the pots and lay eggs too

the fungus gnats flying are not harmful,but the eggs they lay will eat your roots and put tremendous stress on your plants.I bet when you water, it sits on top of the soil and takes a while to drain.Try mosquito dunks.They work great!they are $10 at lowes or home depot.Just put a couple dunks in a bag and crush with hammer.Then spread generously all over top soil.When you water,it activates and will kill the larvae thats in your soil.No more new ones flying around.Just wait about 3-4 days and they should be gone or dead.Reapply with new mosquito dunks every 3 or 4 weeks so they dont return.Its an easy fix using this method.

also if you have spider mites and a sealed room those hot shots no pest strips kill mites

coreyb760@yahoo.com said:

also if you have spider mites and a sealed room those hot shots no pest strips kill mites

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thank god i got rid of them fuckers a long time ago. assholes nearly destroyed an outdoor sweet tooth clone i had. my dumbass not first inspecting the plant, brought it inside and it started infecting my other plants. i got rid of them by removing all the damaged leaves. then with some schultz insecticide, the active ingrediant was pyrethrin. used a whole bottle on my crop then got schultz neem oil extract and sprayed the shit out of the plants every few days. fuckers been long gone ever since. the fungus gnats survived the onslaught but probably cause i wasnt spraying the soil nearly as much as the plants.