Sour Grapes (waterberry, sour berries)

Well rumor has it that there will be some more sour grapes in the ton of grapes we get today from James Ontiveros and his Rancho Ontiveros vineyard. Here's a link to an article about James (and Peter Cargasacchi).

In 1997, James established Rancho Ontiveros Vineyards and planted five acres, all pinot noir, and Clones 113, 114, 115, 2a and Clone 4 from Pommard. He planted an additional three acres in 2000-Clone 1a from Burgundy and two clones from vineyards in California - Benedict Selection (from the Sanford & Benedict Vineyard) and Swan from northern California, from the late legendary, Joseph Swan (not to be confused with T.J Swann, of "Night Train" fame, I think.)

So we will again be sorting grapes by hand to pick out sour berries. Sour grapes are redder and more translucent. They also taste sour because they have little to no sugar. Nobody I've spoken to seems to have a definitive answer as to why this is a problem this year. A limited Internet search on my part found overproduction and poor nutrition to be likely causes. But I'm not sure I've actually found the right symptoms.