White marks on vine leaves

[Anton]

The vine leaves in my son's greenhouse have white marks (see picture). He and his wife are worried it is blight. I know nothing about vines but I do recognise blight on tomatoes and potatoes. This is more like the whitish mould I get on courgette leaves. The leaves do not appear to be suffering and the marks were spotted well over a week ago. Any ideas what it is and what should be done if anything?

Anton

[veggiechicken]

It looks like water drops that have evaporated and left a deposit!
I've no idea really.

[Deltawhiskey]

Wipe one of the leaves with water sprinkle with water and leave it to dry to test. Vines can suffer with fungal infections but I do not believe that is the problem.

David