Pest control concerning gnats in soil

trygrowup · Feb 28, 2026

Take a look at this picture.

I watered some hours before this picture.

I don't know if this is common knowledge but i've noticed this before.
After watering the larves comes up.
The soil looks more wet on the picture because i just sprayed the dirt with neem oil with water 4% + little dishwash

I just think it is a good time to spray neem oil. They certainly don't like it and i find them dead and browning.

I use other means but one thing at a time

Ninjadogma · Feb 28, 2026

trygrowup said:
Take a look at this picture.

View attachment 2608128

I watered some hours before this picture.

I don't know if this is common knowledge but i've noticed this before.
After watering the larves comes up.
The soil looks more wet on the picture because i just sprayed the dirt with neem oil with water 4% + little dishwash

I just think it is a good time to spray neem oil. They certainly don't like it and i find them dead and browning.

I use other means but one thing at a time

You can sprinkle a little bit of DE over the top of the soil. It dries them up from the inside out. Or get some mosquito dunk (BTi) and add a little to your water. It's a natural soil bacteria that wipes them out.

For IPM, the natural bacteria I use:

BT on top for preventing moth and butterfly damage and bud worms

Spinosad on all plant tissue for broad spectrum defense

BTi in the soil for fungus gnats and other soil pests

I use the spinosad weekly, religiously. Mid week and when bugs are observed on the plant, I spot treat with Neem (or insect soap in flower). The BT is saved for flower to prevent bud worms. The BTi is as needed when soil bugs are present.

I have my plants outside in the day and in a shed at night. IPM like this is a must for me. Indoors, your mileage will vary and might be overkill, but none of what I use hurts people or the plant.

trygrowup · Feb 28, 2026

Thanks @Ninjadogma
I'll try to keep things separate.

I'm indoor only and only have gnats.
Also in living soil i don't want to kill fungus.
I'm not gonna use any poison at all except the organic dishwash if that counts.

So good thing you pointed out that you move your plants and have other pest concern.
Thats important info for me and others.

Thanks again for the recipe and i hope more will share their metodes and results along with mine.

Ninjadogma · Feb 28, 2026

trygrowup said:
Thanks @Ninjadogma
I'll try to keep things separate.

I'm indoor only and only have gnats.
Also in living soil i don't want to kill fungus.
I'm not gonna use any poison at all except the organic dishwash if that counts.

So good thing you pointed out that you move your plants and have other pest concern.
Thats important info for me and others.

Thanks again for the recipe and i hope more will share their metodes and results along with mine.

Doesn't matter what you do, just that you have an IPM plan and that it works for you.

Vick_Vinegar · Feb 28, 2026

Hypoaspis miles are your best bet for control. They are cheap to buy if you can't get em to propagate. I always use a shovel full of yard soil in every cook from a humus loaded area which is loaded with them.

Good for a living ecosystem. They will march around your medium and eat all the gnat larvae.

I haven't had to treat for gnats for years thanks to these little guys, and I water every day from the get go.

Your browser is not able to display this video.

Always a big promoter of predatory control when it comes to gnats.

trygrowup · Feb 28, 2026

Vick_Vinegar said:
Hypoaspis miles are your best bet for control. They are cheap to buy if you can't get em to propagate. I always use a shovel full of yard soil in every cook from a humus loaded area which is loaded with them.

Good for a living ecosystem. They will march around your medium and eat all the gnat larvae.

I haven't had to treat for gnats for years thanks to these little guys, and I water every day from the get go.
View attachment 2608197
View attachment 2608198
Always a big promoter of predatory control when it comes to gnats.

Thanks man.

I saw those small fellas in my last grow. I had many.They didn't seem to mind the neem oil.
I was actually thinking about taking a handful of the soil and put in the new but i did not know what these were.
I tried searching a bit on the net, but didn't find them.
Now that i know i will do that.

Hypoaspis miles. Good info thanks

Vick_Vinegar · Feb 28, 2026

It's handy to think of it at management as well, not eradication. A few stray gnats isn't an issue. If you set your heart on complete eradication end up with zero larvae the hypoaspis will pack up and leave or just eat the larvae or eggs of other beneficial creatures in the medium It's all about having a self sustaining ecosystem where everything is in balance.

I'm at that stage where I'll have a flyer here and there but don't see any active larvae. They must be there as the hypoaspis are happy, but they are in control to a point where gnats aren't an issue.

I'm never one for aggressive pest treatment, more pest management. A thriving living ecosystem will generally manage itself but will need a bit of guidance here and there.

trygrowup · Feb 28, 2026

Right up my ally @Vick_Vinegar

Thanks for pointing in the right direction

Ninjadogma · Feb 28, 2026

....
sorry, wrong room

trygrowup · Feb 28, 2026

Ninjadogma said:
....
sorry, wrong room

Nah your good bro.
There should be something for everybody, so everything can be an inspiration

Vick_Vinegar · Feb 28, 2026

Ninjadogma said:
....
sorry, wrong room

I've dumped in mikedins journal a few times when notis are coming in hot thinking i was in the wreck haha.

Happens to the best of us.

Coconutz · Mar 1, 2026

I completely eradicated fungus gnats without spending money or using poison.

A bag over the pot stopped them getting in/out to lay egg and I could squish them with ease.

A pair of scissors works well at this stage, after watering I'd be cutting them in two.

My mums, I put each of them in a bag

Fungus gnats hatched up to 10wk iirc, Google 4wks isn't accurate!!

Up to 5 gallon iirc?
You can buy these paint bag filters iirc they're 60 micron they keep gnats in/out they're only £1 each if you don't fancy plastic?

The foundation is there for a good gnat proof screen.
If you sew a draw string top and bottom of the paint filter bag then it would fit any size pot, elastic in the stem drawstring would essentiall

I keep my pots covered it helps prevent fly by egg laying but they're not a guarantee, covering them yeilds other benefits for roots and helps with evaporation/humidity, preventing any interface for salt crystals forming preventing roots from growing in the stratified area.

That sounds like a bunch of bull but the results are visible

It's all a waste of time if new gnats are getting in, if you're using soil you're almost guaranteed to have gnats thats just the way it is, however if there's no new source you can wipe them out

trygrowup · Mar 1, 2026

Thanks @Coconutz

This is brilliant.

You overtook me from the inside there.

I'm going to make something a bit like that. But made from two layer of a white sheet. with some strings to tie it. But only the top of the pot.
I like the white and i wish to hold a little more on the moisture for the same reasons you mention.

Many thanks for your input

chitownglass · Mar 1, 2026

Put a half inch layer of diatomaceous earth on top of your soil ad bottom water for a week or two instead of top watering. That usually solves my problem.

MrSativa · Mar 1, 2026

chitownglass said:
Put a half inch layer of diatomaceous earth on top of your soil ad bottom water for a week or two instead of top watering. That usually solves my problem.

Thats my way to go also

Gmix · Mar 1, 2026

Personally, I use nematodes.
You can buy them online easily.
It’s a once only application they will munch the larva for breakfast in no time
Especially good for heavy infestations.
De I’ve tried however it has it’s limitations drawbacks & once wet is no good
It only works when dry.
I’ve honestly and I crossed my heart and hope to die seen them crawl through wet de no problems witch ever way you go
Good luck bud

Coconutz · Mar 1, 2026

I've used nematodes but only as a preventive measure after catching a gnat in my room.

Your browser is not able to display this video.

It seemed logical that I'd get problems, at best a gnat had spent 12 hours or worse it hatched in there either way = trouble I thought.
It turns out it's not quite that straightforward they need the right conditions to lay eggs, my coco has been recently repeatedly apparently that makes it less appealing to gravid females as it didn't amount to anything.
Idk if that's because of the nemetodes or other reasons

trygrowup · Mar 1, 2026

Gmix said:
De I’ve tried however it has it’s limitations drawbacks & once wet is no good

Thanks @Gmix

No good when wet sounds terrible.

I tried nematodes. It worked.
Reason i*m not a fan is prize and also, I don't really know if they survived the transport

Good info thanks

Week4Bytch · Mar 1, 2026

I have to use the whole gamut... BTI, Predator bugs, Nematodes, and yellow sticky traps. The struggle is real. Garage growing has its plus and minuses. We're managing.

Coconutz · Mar 1, 2026

When I researched nematodes just briefly it wasn't a deep dive or anything, i read they'd die out without food, that's obviously true but no food in medium is a bit of a stretch it's unlikely to happen there's a ton of life they're happy to eat.

Your browser is not able to display this video.

I'd need to check to be certain but I think it's about 6 months between applying them and checking the samples and finding them.

Pest control concerning gnats in soil

Pest control concerning gnats in soil

trygrowup

Ninjadogma

trygrowup

Ninjadogma

Vick_Vinegar

trygrowup

Vick_Vinegar

trygrowup

Ninjadogma

trygrowup

Vick_Vinegar

Coconutz

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chitownglass

MrSativa

Gmix

Coconutz

trygrowup

Week4Bytch

Loyal To The Soil

Coconutz

Pest control concerning gnats in soil

Pest control concerning gnats in soil

trygrowup

Ninjadogma

trygrowup

Ninjadogma

Vick_Vinegar

trygrowup

Vick_Vinegar

trygrowup

Ninjadogma

trygrowup

Vick_Vinegar

Coconutz

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trygrowup

chitownglass

MrSativa

Gmix

Coconutz

trygrowup

Week4Bytch

Loyal To The Soil

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