Fungus Gnats.

I've got them. Fuck. I knew there was something fishy when the perlite on the top of my soil turned lightweight green. What should I do? I was told something about draining my water with a soapy mixture? I don't know but they're really annoying. Suggestions please and thanks ahead.

No pest strips...the green on the perlite is just algae and it doesnt hurt anything

If you're really worried about getting bugs Neem Oil is always a good way to go...it's natural.

I have a pretty detailed play by play on the epic battle of Fungus Gnats, check out my journal. It's a 2 week battle where you slowly see results.
Question - what kind of soil did you start with? Did you use Peat moss containers too?
I used some organic crap that had them in it already and I didn't notice them until 2 weeks of vegging. I thought i was the peat moss decomposing that made them but I recently added some more soil to the pots and it had a ton of those little bastards flying around in the bag. I did open it about a month and then I resealed it, but I guess it wasn't sealed too tight.


My weapons of choice

- diatomaceous earth
- 3 in 1 fungus killer
- Hydrogen Peroxide
- fly strips resting on the soil. Unfortunately my state doesn't have HOT SHOT fly traps.

I have the same problem too. I had them last year, but not as bad as this year. I have several gnats flying around the room and larva in the soil. They killed 6 clones that were just rooting so far. I pulled them out of the soil and I seen a couple of really small looking white worms with what looked like black or brown heads. They were munching into the stem of the clone I was looking at. I hung a couple of fly tape things and I just bought some stuff called Sevin from home depot which is safe for vegetable and stuff. I luckly only have them in my veg room and not my flowering cabnet. The flying ones have so far been landing on the tape. I hope to kill the larva with the spray. Not sure if I would use the spray on flowering plants, but I would think plants still in veg would be ok. It says it's ok for vegetables.

Step #1 is let your soil dry out. Let your plants wilt from lack of water. That will kill the larvae. Hang pest strips up to catch adults.

The cause is from having the soil wet/moist all the time.

Dirtyboy said:

Step #1 is let your soil dry out. Let your plants wilt from lack of water. That will kill the larvae. Hang pest strips up to catch adults.

The cause is from having the soil wet/moist all the time.

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I've read that if you dry it out it haults the reproduction but once you water it again it begins.
I realized keeping it drier than wet does help keep the numbers down, but I don't think they die from drying out the soil. Would love to hear from experience tho.

here is what i did i went to home depot and bought a 50lb bag of play sand and put about 1 inch ontop of my soil. there were gone the next day except maybe a couple of stragglers but the shit worked perfectly.

Sand on top of the soil is supposed to prevent the larvae from emerging from the soil to become adults, and also keep the adults from lying more eggs in the soil.

akgrown said:

here is what i did i went to home depot and bought a 50lb bag of play sand and put about 1 inch ontop of my soil. there were gone the next day except maybe a couple of stragglers but the shit worked perfectly.

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Do you leave the sand on there permanently? Can you just go to the local playground and take that sand without worry of bringing some nasties?
I read that it hurts the oxygen getting to roots. Sorry to hijack this post but I have issues with gnats.

akgrown said:

here is what i did i went to home depot and bought a 50lb bag of play sand and put about 1 inch ontop of my soil. there were gone the next day except maybe a couple of stragglers but the shit worked perfectly.

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Yep yep yep! That will keep it dry. I bet it worked great. They love to appear in damp soil.

Thanks for some suggestions guys! What I've done so far was... Hunted for them one by one for awhile. Got a good 30 or so. Thats most of the population. I don't see many adults, I'm now able to tell adults from the youngings. 60X Microscopes are fun while high. I will still have the problem but I'm going to try to get some fly traps soon. I've also heard that if you put a layer of perlite ontop of the soil it'll help too. I did that with one plant before I ever thought of doing it for reflective purposes only and then I noticed that that plant doesn't have much flies around it as much as plants with the damper, less perlite mixture.

Peter421 said:

Thanks for some suggestions guys! What I've done so far was... Hunted for them one by one for awhile. Got a good 30 or so. Thats most of the population. I don't see many adults, I'm now able to tell adults from the youngings. 60X Microscopes are fun while high. I will still have the problem but I'm going to try to get some fly traps soon. I've also heard that if you put a layer of perlite ontop of the soil it'll help too. I did that with one plant before I ever thought of doing it for reflective purposes only and then I noticed that that plant doesn't have much flies around it as much as plants with the damper, less perlite mixture.

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If they fly they are adults.

Scubasteve420 said:

Do you leave the sand on there permanently? Can you just go to the local playground and take that sand without worry of bringing some nasties?
I read that it hurts the oxygen getting to roots. Sorry to hijack this post but I have issues with gnats.

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Another way to kill the larvae is to put raw potatoe chunks on the top soil to suck up all the larvae. Worked so far for me. Remove the potatoes every 1 to 3 days and replace if you want to keep them out.

Way too many suggestions. The first reply was the correct one. No pest strips, period. They are $5 each and work for everything! It's so crazy to read about people using all these crazy time consuming and costly methods when all you have to do is hang a 6" "air freshener" in your garden and everything with more than 2 legs is dead in a couple of days with absolutely zero harm to your plants.

Hang 1 NPS for every 100sq ft of garden space approx. a foot above or below your plants. Try to minimize air circulation and prolonged time spent in the garden by humans for 7 days. Take the NPS out after 7 days and put them in a zip lock bag for future use if needed.

If you take this advice you will save yourself hundreds of dollars and hours. To hell with all that hippie dippy crap that costs money, takes way too much time and then don't even work.

Accept no substitute! http://www.drugstore.com/products/prod.asp?pid=88409&catid=137131&aid=337953&aparam=hot_shot_no_pest_strip_&CAWELAID=61273448

Went with the no pest strip, seems like the best solution because I wouldn't want to harm my plants with a soap waterdown or neem oil. I hope this catches them seeing that most of the gnats stay around the side of my pots. Oh well, more defense now though. Before I just had my HPS zap them

Is it good to hang one of these even if you don't have pests.. to help prevent the problem from ever occurring?

azkabanthereeferman said:

Is it good to hang one of these even if you don't have pests.. to help prevent the problem from ever occurring?

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I know people that do, but I personally don't and wouldn't recommend it as this stuff IS toxic. I'd suggest you only use them when you have confirmed an infestation. Hang them 7 days for mites and 14 days for fungus gnats. Then put them in a big ziplock bag in case you ever need to use again.

Peter421 said:

Went with the no pest strip, seems like the best solution because I wouldn't want to harm my plants with a soap waterdown or neem oil. I hope this catches them seeing that most of the gnats stay around the side of my pots. Oh well, more defense now though. Before I just had my HPS zap them

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In a day or two you'll see a bunch of dead adults on the ground. If you keep one up for every 100sq ft of garden for 14 days you won't see any signs of them again unless you get reinfested with a new colony.

BasementGuerrilla said:

In a day or two you'll see a bunch of dead adults on the ground. If you keep one up for every 100sq ft of garden for 14 days you won't see any signs of them again unless you get reinfested with a new colony.

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Thanks. This morning I checked to see a bunch of gnats dead on the floor and not a single one flying! Great solution to my pest problem.