Answer: Based on your description I am not certain what this is, but it could be the grape flea beetle. There are terrific close up photos at the following entomology web pages so maybe you will be able to tell if that is it, or not. (You may need to cut and paste the complete url into your browser to make it work correctly.)
Here is climbing cutworm information, another possibility.
I would suggest you consult with your local county extension to make a definite identification of the pest and then based on knowing that, determine what to do. If a chemical control is needed, they will have the most up to date information on what to use and how/when is best to use it.
Also, be sure to do a thorough clean up of all grape foliage and debris as well as prunings this fall and winter to try to limit their overwintering. Good luck with your grapes!
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