Fungus Gnats


Well-Known Member
I have been seeing alot of posts about people seeing little black bugs all over their soil. Often times these are fungus gnats and they can even come in top end soils. Especially ones that dont sterilize their soil.

This link describes exactly what these are:

fungus gnat.jpg

Luckily these are very easy to get rid of if, and there are many ways to rid your garden of these pests. As long as you catch it before full a on infestation.

Heres what to do if you only notice one or two.

Good thing you caught it early. If you notice one of these little buggers crawling around on your soil, stir up some soil and see if more come out. This will give you an idea of how bad it is. If you can only see a few, add a layer of sand or perlite. This prevents the adults from laying more eggs. Then, let your soil dry for an extra day or two. This should drive the adults away and kill the eggs and larvae.

Next, water normally and keep a close eye on your soil. It may take a few days for them to return if this method was unsuccesful.

You can also try the yellow sticky paper like the link said but this will only kill the adults. The larvae will continue to chow down on your roots.

If that doesnt work or you have a pretty bad infestation relax. Their larvae will feed off your roots if you dont do something quick but again, they are really easy to get rid of. There are a number of commercial solutions you can buy. I cant name them all here but Azatrol and Gognats came recommended to me at my local indoor garden store.

But by far my favorite TRIED AND TRUE METHOD is dish soap.

I know it sounds like it is the last thing you would want to put in your soil but it completely solved my problem. Ill tell you what I did and you can adapt the quantities to your setup.

I was growing two plants in 3 gallon pots with Fox Farms Ocean Forest. During week 3 of veg I noticed a couple of gnats. I didnt have any perlite so they returned after I dried the soil.

It took them about three days to return. After that I fed each plant with my normal nute lineup. Then I took a half gallon mild jug of water and put 2 to 3 drops of regular Dawn dish soap. Then I topped each plant off with a quart or so of the soap solution. And my plants lived happily ever after (till I killed those hermies!).

I know its hard to believe that it works but it does. I thought my old lady was telling me an old wives tale when she told me about this method but after 5 days of nagging I caved.

If anyone else knows any other methods please add them.

Wonder if that dish soap stressed your plants out and made them hermie... sounds like a good idea but i dont think i can bring my self to pour any kind of dish soap in with my water. Guess ill stick with sand, the thing about sand is it does keep them down but doesnt really get rid of them, because when you water its impossible for the sand to not mix in with the soil, also as the soil drys out the sand and soil moves around opening up cracks and edges where the fungas gnats can still get out. basically its impossible to keep the sand fully covering the soil, i applied the sand method twice in two weeks and its a real bitch
i have a hot shot no pest strip and from what i understand thats a sure fire way to get rid of them, but its also suppose to be really dangerous if people are around it 24/7 because apparantly it has some kind of poisen in it that could possibly give me cancer or mutate me. im not in a vented place really and my bed would be about 7 feet from it, but honestly im so tired of these little bastard gnats im about ready to pop open that no pest strip and take the gamble, what do you guys think should i do it i think i might, leave that thing in my room for like two days and let it kill all adult gnats and hopefully wont kill me then ill throw it away. its only 6 bucks and from what i understand it kills them fast and ill take the gamble of living and basking in the poisen for a day or two its worth it for me ladies to shake the gnats. Fuck fungus gnats


Active Member
Mild soap does amazing things. Spray your plants with it, put it in your water...won't hurt the girls at all and gets rid of all kinds of bugs. Been doing it for years without any issues. Also, use it in your other gardens, won't hurt veggies either.


New Member
Mild soap does amazing things. Spray your plants with it, put it in your water...won't hurt the girls at all and gets rid of all kinds of bugs. Been doing it for years without any issues. Also, use it in your other gardens, won't hurt veggies either.
Ivory dish liquid 1-3 drops per gallon...every gallon everytime...eliminates dry spots as well


Active Member
What if you've got gnats in an aero system? will the soap still work? I apparently bought some clones that were started in peat plugs that had gnat eggs. I really need to get a handle on these little bastards!


Well-Known Member
I'm having this same problem. Just started I have only seen maybe 10 adult gnats max. I had thought I burned 2 of my plants and thought it was weird from a mild mix of nutes and did nothing to the others. Well my area recently flooded and apparentally these wet soggy grow bags attracted gnats. I sprayed lightly cause(Im about 25-30 days from harvest) with pyrthium mixture to kill the adults. Now I was thinking of trying to kill their larvae with mosquito dunks and drench with azamax solution once they dry out. What do you guys think? The larvae stage is the most harmful as they eat the roots and I'm close to finishing.


Well-Known Member
Thanks for the reply.

I have read about
diatomaceous earth and any further plants I use in soil indoors or out will have this the top 3" inches

I'm switching to hydro in the next few months so looking just to get rid of the larvae in my soil to get rid of them as the adults are all dead already. I can't spray my plants anymore or will have to worry about mold.

I'm hoping when they dry out a lot will die and then I'll drench soil with mosquito dunked water and a high dose of azamax and should take care of it.