fungus gnats

What's the best insecticidal spray for fungus gnats I've been told to use Neem Oil. I'm an organic grower and right now I'm just cooking my soil and noticed this morning I have lots of fungus gnats on the top soil. I don't have plants yet, just soil.

So when I started growing outside this year for the first time in soil (I'm a hydro/coco indoor grower, so it's a very different experience!) I initially had a HUGE infestation of fungus gnats. I didn't realize how badly I was overwatering my cannabis seedlings at first. I was soaking the young...