Yes, it is the little buds. Last year, the surviving buds
did turn into grape clusters, but the percentage left was
quite low because of this [it was the first fruiting year for
this plant so I didn't question it - and there were the ants
and an occasional snail]. I'm wondering how growers [can]
deal with this. Hopefully, before it's too late, I'll get a
chance to visit one to find out what they know. I'll follow
up if and when I learn more.

Ed