Sounds like one of the scale insects - google scale insect for pics to make sure. As its a grapevine, if it is scale, I'd use methylated spirits on a disposable cloth of some kind, don't saturate the cloth, just wet it with the meths, then rub over the affected areas, scraping off the little blighters as you go. You may need to repeat later on, there seems to be a plague of scale this year... Alternatively, you can use horticultural soap and wash them off. If you have some difficult to get at ones, dab each one with a cotton bud dipped in meths.

Hi, Bamboo I've checked it out and I think you are right, they are scale insects, they're horrid , it's a real plague, no doubt. Do you remember that a few weeks ago there was something attacking magnolia stellata ? Well I think that it is the same thing .Thanks for the info-- a busy day ahead tomorrow ,OH says that I should use some of my homemade wine to remove them, that will teach them!

Ooh, your wine's as bad as that then, is it, lol!

My wine is fine in emergencies , Bamboo . When we lived in Saudi he was very pleased that I could make it . He just prefers the bottled stuff [ so do I] , it doesn't stop me making it though !