Bake your dirt!

[OldSoul]

I've noticed fox farm mediums come preloaded with bugs. They will eat your plants as fast as they come up. 220 for a couple of hours seems to do the trick.

[Gingerbeard]

I always bought my soil well ahead of time for the bug reason. Left it out for several months to dry.
You cannot avoid bugs in store bought soil.

[OldSoul]

Believe it or not 2 hrs isn't long enough, It has to get like you said completely dry. I got some diatom????? Earth coming. Thrips are what I think I'm encountering, or fungus gnat larvae.

[Bluey]

The solution for that is not to use soil indoors.

Cooking or baking soil is part of the composting process. It should get hot enough to kill most bugs in the soil but they may thrive on the outside of the soil but still under the cover.

[shadycon]

I found out the hard way. bought one bag with worm casings etc. and it was wet and full of fungus gnats. As much as folks say about these kind of soils they should warn new growers about the bugs they are buying. I'm doing just fine with regular potting soil with no added fertilizer, I'm using Fox Farm trio and calmag. Still learning

[Gingerbeard]

Let's not forget about diatomaceous earth, huh? When I started mixing that with soil, I had fewer gnats.
I don't know how much. Probably more than recommended. That's a sort of thing I do.

[Rwise]

Baking soil will kill the bad things, bad thing is it also kills the good things.
I have baked soil also,

[Bluey]

You could bake it around 55 to 65⁰C. Will kill the bugs and eggs Id imagine and the microbes will love it.

[OldSoul]

Turn out you need more than a few hours, you have to completely dry it out because the moment you water it the soil comes back to life. Trying the D-earth method today.

[Smallgrow]

I’ve had bugs in soil too, but I feel like if you’re buying premium soil for cannabis , from a good grow store it should not contain bugs. It can obviously be a problem, but a good supplier should be taking steps to avoid this. The producers defiantly are. If you buy it at box stores or Amazon you’re asking for trouble, although I know this can be the only option for some.
As a living soil grower I agree with Rwise you’ll kill good stuff with the bad stuff

[iwanttoknow]

I have had a problem for the 1st time with gnats! Been growing indoor since 2019 always with Fox Farm Happy Frog soil and trio of nutrients. The crop currently growing has been the absolute worst for gnats in the grow area, I've been spraying with insectidal soap from the garden section at Home Depot. I always buy a new bag of Ocean Forest for the bottom 3rd of the grow bag and fill the rest with new bags of Happy Frog. I never reuse the soil that was used for the crops, it gets dumped outside in low spots in the yard or added to the vegetable garden area. I don't know what else I can do, any suggestions are appreciated, other than putting the soil through the cooking/baking process.

[Bluey]

Allow the top inch or two of the soil to completely dry back between watering should take care of them.

[Gingerbeard]

I got this.
Fans. Get a good flow of air across the top of your soil. If you are in plastic, you also need to flow some air at those holes. If in fabric, just the tops should do you unless you have nasty bags. Make sure any drip tray you might have is dry and the bottoms of whatever container you use are not flat on the ground.
Since they are fungus gnats, they are flying to and for the fungus in your soil. If they cannot get to that fungus, they have no interest in being there. If you keep a good flow of air going across your soil, the gnats cannot readily do their thing. I'm going to give you a personal guarantee that sufficient air circulation across any exposed soil will keep any flying and most crawling insects out of your soil. I don't know what to back that guarantee up with, so I'll call it an unbonded guarantee.
In the future, mix in diatomaceous earth with your soil before you plant. That also helps.
Now, someone is going to tell you how to treat with DE mid-grow and yellow sticky paper. Take it away.

[Bluey]

I use a fan down low that moves air around below the canopy and across the top of the coco and since doing that haven't had a problem. The top of the coco doesn't really dry out either so I'd say that is definitely helping.

What's wrong with Pink sticky paper?

[Gingerbeard]

Science.

[Smallgrow]

Sticky paper won’t solve a bad problem but I find if numbers are low it’s very helpful to eliminate a few before they turn into a problem. I use it in my grow tent and microgreen set up. I costs almost nothing and is simple to use just set them on the edge of your pot