Skin on Interlaken grapes have spines this year.
Not sure if this is weather related, some weird disease, or a normal grape thing. This is the 3rd year for this grape vine and the first year that we are letting grapes set on the vine (other than 1 cluster that I didn't see to prune off last year). Last year that one cluster produced smooth skin grapes. But all the clusters this year, the grape skins have bumpy spines (kind of like you find on prickly pear cactus fruit). I am including a couple pictures. Any thoughts?
Douglas County Oregon grapes
I have never seen that before. It looks pretty uniform across all the berries and clusters which would make me think that it is related to a spray or to insect feeding. I would dissect the berries to look at the structures under a microscope or magnifying glass. If you would like, bring some grapes in to the Extension office and the Master Gardeners or I can look at them under our microscopes. That is definitely an odd type of damage.