Just doing it that one time never caused a Herm. for me, but I had to do it so I didn't have to go back to my gardens til harvest just to try and get the males. This way I always had 0 seeds in my buds and less chance of making a path, being seen or running into game warden, cops etc. I've found that certain strains seem to be more prone to herms than others and I would not ever use those strains once I found them. Like tckfui said if you really stress them you can make em go that way. But not just once on something that has hardly begun to bud.