Did it one time - sprayed 1 oz of 6# lv.  Cupped the leaves a little but that was it.  They were my best beans that fall by 10 bpa.  Never had the nerve to do it again. I spray beans around the yard all the time w/a ru/2-4d mix that I use on the driveway and it usually takes 2 or 3 sprays to get them. 

Not sure if I gained any better weed kill