I'm seeing what you are saying about the nematodes getting some time to get going.. I'm seeing larvae that have been nematoded (brown, dead, ripped apart) .. but there are still plenty of healthy ones..
If you started this around say wk 3 of flower, you would still have the gnats all through the crucial wk 4, 5, 6,,, maybe more.
I picked up a USB scope to help out with the research.. still figuring out how to use it though..
Well.. I'm back to take the verbal beating I totally deserve for this thread. You all @pseudobotanist@vostok ('cept @hotrodharley pest/plant parasitic confusion and denial) were right. I couldn't get the nematodes to do the job.
I had to retreat into using Gnat Nix AND testing with using perlite as a substitute for sand.. to ensure I got a nice crop.
With my next crop.. I will try a different brand of nematodes. I have spoke with the supplier and he is familiar with the nematodes I used and assures me his line will work better.. we'll see.
So anyway.. I'm back to admit you were all were right. I didn't get the nematodes to work very well. And blockage (like sand) appears to be the better route to take.
I'm hesitating to use sand though.. not sure why exactly. Something about the density of it layering the soil line.. ? .. trying perlite out first. And Gnat Nix DEFINITELY works, very damn well. Just too fucking expensive. I used Gnat Nix all through veg.. Nix'd them totally.