I'm typing this with a case of "pesto-finger" - the stubborn stains that take a few days to fully wash off my thumb and fingertips from hours of picking basil leaves (mostly after harvesting all the remaining basil in the face of a frost.) I always wonder (for a few days a year while I'm doing it) how basil is prepared (before the grinding in a pestle or food processor) both "traditionally" and/or in a large-scale or even commercial operation to make pesto, as I'm tediously picking leaves off of the stems in my annual home production. Is there a better way than tedious hand-picking?
My personal pesto has wandered fairly far from "pesto Genovese" but that really has no impact on this question, as it's still mostly basil.
Looking carefully at the picture Lars provides, it would appear (upon examining the picture at full scale) that the basil is being harvested fairly young (no flowers) and simply being cut off (you can see a sickle-bar type cutter at the base of the harvester) and pulled up (unfortunately the picture appears to be posed, with the harvester stopped and not actually harvesting, based on nothing on the belts nor coming out the chute.) This actually makes some sense - the stems at that point would be fairly tender and might not be objectionable when ground up. While it will take some discipline to finish off basil that could grow more (after years of trying to give it as long as possible and getting it right before frost), I'll have to try some this way next year. I might also try a side-by side taste comparison with some (of the same age) hand-picked (or fist-stripped) from the stems and processed, to see if there's any detriment form the young stems.