I have an old grapevine in the backyard. We normally don't eat the grapes, though they were very good when the plant was younger. Now it is primarily decorative. Today, I looked out and it looked wilted, as if not watered for a while. This evening it is even worse. We have had a lot of rain, so lack of water is unlikely to be a problem. It has several fully developed bunches of grapes. Any suggestions? Carol in Ashland, KY
Check the main trunk of the Grapevine for any signs of a canker. A canker could be girdle the tree and cut off water and nutrients to the plant.
Wilting can be a sign of this.
These links will help you.