Depends upon the bug, really.
I’ve not grown weed before (not currently legal where I live), but I have grown some ethnobotanicals – S.divinorum, B. caapi and the like – and as far as I can tell nothing works on whiteflies (which is really only is an issue for indoor growing). I tried lots of things (including naturals like Neem and Pyrethrins), and nothing worked. When I moved out of that house I had to sacrifice the plants to prevent them from coming to my new digs.
Also, I imagine that geography matters. Maybe in Australia there are different pests than, say, in the Ozarks.
