Netting is the only real solution.

The same thing happend to me last year only it was flies ! Nothing deterred them , fly-paper ,smoke , jam traps , it is so disappointing .
This year , so far the few interested parties have succumbed to fly-paper !
What I did this Spring was to hard prune to two buds and cut back excess foliage regularly . The bunches are much less crowded , look very healthy and fingers crossed I am hopeful of a decent harvest . It is an ancient Homberg [black grape ].
You have my sympathy ,and I hope that you don't lose a
all the crop .
Welcome bye the way .

Suggest you find where is the nest. If you can..... try and deal with it. We once had one about football size in the attic and they were everywhere. Or cut the top off of a plastic drinks bottles about 2/3 up, and put cheap beer, if there is any now. Reverse the top into the fluid. It was very effective at an outdoor function we went to recently.

Good idea Dorjac!