Hope he's got 'em nailed by now, guys. This thread is from 2011.
Hope nobody uses Merit75 against fungus gnats.
Lots of organic ways to knock 'em down, cinnamon, rosemary oil,
diatomaceous earth, sand, nematodes, OG BioWar, Mosquito Dunks, etc, etc.
Only way to keep 'em from coming back is to stop bringing soil/coco/water into your garden, and never ever use worm castings or anything that contains them. So.....
I'll put up with a couple fungus gnats. They usually never reach an annoying level with the regular use of OGBiowar, but if I didn't have that, I'd grab Mosquito Dunks (organic farmers only) or
Spinosad for a root drench.