It is a Rose Chafer and in large numbers they can get on the grapes and chew them bad. I is especially bad pre-bloom as they feed on the tender bloom clusters and will ruin the crop.
Sevin works well for them.
Not sure that's a rose chafer. The color looks to be a bit more brown and the antennae look longer than a rose chafer. But whatever it is, they are obviously not something you want on your vines.
I have a lot of rose chafers out here right now and they do chew on the leaves of mainly my apple trees. I spray as soon as I see them and it knocks them back pretty hard.
It could be something else besides a rose chafer although they do vary in color a bit and the antenae in the picture is a bit unclear. Whatever beetle it is carbaryl (Sevin) is very effective. Just don't abuse the use of it. It has a negative impact on beneficials as well as the target pest so only use when necessary.