Thanks jay jay - I have now found out that they consist of more than one shoot coming out of the same bus (there are usually 8-10 buds on each "lat") and you get rid of the one that is least in line with the row you are working on. My guy from the local winery tells me that this is over-elaborate so I needn't bother! Instead, he tells me that there is a legal requirement to spray in June against "cicadelles de flavescence doree", which I've now done - let me know if you want any details.