grapevine problem

My Black Hamburg had "bunches of raisins" last year.
It was so hot and dry that the vine became very stressed, caught powdery mildew, shrivelled the fruits, then the leaves all dried and fell off.
I thought it had died, but during the winter I scraped off some bark and it was still green in some places. I cut off the dead twigs (about half the vine) and then left it to get on with things.
It is now growing happily again, despite the recent very dry weather.

I suppose, what I'm saying is; has your vine got too large, so that it can't get enough water?
Or is something growing nearby and stealing its water?

Thanks for that info, but I don't think that is the problem, the vine is not competing with any other plants for water or feed, as it is in the border of the greenhouse by its self, the greenhouse is 19' x 6', and the vine is trained along the apex and down six of the glazing bars, I might also add that I have an irrigation system in place which waters the plant twice per day for approx 10mins each time.
Once, a few years ago it may have become stressed as it did get powdery mildew, but I put this down to the fact that the previous year it went beserk with fruit, and I could'nt be bothered to prune, so I just left it to its own devices, havent had mildew again?

I do however, de-bark the vine in the dormant stage every three or four years, to prevent build up of possible bugs though, and to generally tidy the vine up, as I mentioned earlier about the virus thing, it may have got damaged then and allowed whatever virus the garden centre told me about to enter the vine.

Thank for the help though

Hi , can you explain debarking please ??

ive been cutting my 2 vines back too hard over the past 2 years no fruit

this year i cut back to about 6 buds going like mad with flowers !!!!!!!

Hi Biffo17
Debarking is the process of stripping the old bark off the vine, after e few years the bark becomes cracked and peels, and as a result of this, it can harbour over wintering pests such as red spider mites or other blighters who may harm or spoil the fruit,. the process is rather tedious, as you have to peel all the bark using your finger nails to get started, just scrape into the older part of the stem, then pull all the bark of to reveal a smooth brown stem, you wont get it all of, and around the lateral spurs/rods it will be quite difficult, I have never been bothered with red spiders or any other bugs as a result, hope this gives you an insight to this process, picked it up from an old gardener who I recieved the cuttng from some 30 years ago, he swore by doing this, mind you, he was vertually a full time lotty anorak, but good as gold and had some good advice.
Happy peeling in the future, but as I said it is rather tedious,
PS If your vine is flowering, you could try stroking your hand over the flowers when they open this will result in pollination of the flowers, be gentle though as not to pull the immature grapes of the vine, and you should have grapes developing within a couple of weeks, keep the vine watered and fed at this stage, critical, or you may loose the grapes.
Hope this is a little of help to you

Geordie Geoff AKA open-cases