sick grapes

Every year I look forward to a feast of grapes.  I planted a sickly valiant grape vine about 15 years ago.  It was just 2 feet tall and half dead, and then when my husband mistakenly took a weed whacker to it, I thought it was over.  But it came back better than ever, and it looks much older and gnarlier than it should.
Valiant produces big numerous clusters of dark blue grapes, which taste amazingly grapey.  They are only the size of big blueberries, and they each have at least two seeds, but they sure are good!

This is what they are supposed to look like in early September - still green, but plump and starting to turn dark.
However, this year, just a very few clusters look this good.

Most of the clusters look like this.  The grapes are wrinkled and sunken and covered with grey mould.

Many of the leaves are also covered with tiny dark dots and look faded and mouldy.

My internet research has come up with two likely  culprits:  Botritis cineria |(grey mould) or black rot.  Either way, there seems to be no cure.  Advice includes pruning excess branches to improve air circulation, cutting off and burning infected leaves and fruit, and even destroying the whole plant and not planting another grape vine in the same spot for at least 10 years, because the fungus pathogen can live in the soil that long.

So I will have to hang on to good memories of tasting the grapeyest grapes, and enjoy the vines as a privacy cover, not as a source of a delicious snack.