Identify strange woody growth
I have sent your question to the Enology Department at the U (Annie Klodd) and I will let you know when I hear back from her.
I heard from Annie.
This are called aerial roots. They are harmless, but the vine produces them when there is too much moisture: either saturated soil or too much humidity in the air, or both. So it is a sign of stress, but will not in itself hurt the vine.