The concentration is weak. You have to use a ridiculous amount.
Gnatrol wins again.
The great thing about GnatNix is it isn't a pesticide. 1 application on the top of the medium at the beginning of the grow and it stays there working for the whole grow. I suppose if I couldn't get rid of the flying adults then I would spray the plants with something but remember the bug spray will likely show up in the lab test.