I did a search for Dow General, and came up with this:

http://pmep.cce.cornell.edu/profiles/herb-growthreg/dalapon-ethephon/dinoseb/herb-prof-dinoseb.html

back in the mid-1980's, I remember using Premerge on alfalfa seedings.  It was basically the only thing we had at that time to control common chickweed in new alfalfa seedings.  From what I remember, it was yanked because it was a suspected carcinogen.  However, I was unhappy, because at that time, we had no real alternatives.  Not long after that, we got Pursuit.   At least, that's the way I remember it.