Co2.
If you have a sealed environment, (or one you can seal up temporarily) get yourself a tank of Co2, seal your room and bomb it with that. if you can keep the co2 levels high enough, youll deprive the bugs of o2 and they will sufficate. it works.
a few things:
its easier to do with a cloner (smaller tent, easier to maintain high levels)
do it with lights off, i know i know, plants and lights off co2.. take some bad with the good
if you use dirt, do a soil drenching in the proccess to flush them outta hiding.
clean the shit out of the room (of course)
and do it again 1.5-2.5 days later.
organic and clean
nothing lives without o2