By Canalhopper
Denbighshire,
United Kingdom 
Please can I have some advice about my grape vine.
It’s growing on a pergola, and a lot of the leaves have brown spots on top and grey mildew underneath. I believe it’s botritis?
Is there anything I can do to stop it spreading, or to make it go away? Would it help if I removed the affected leaves—there are quite a lot!
I’ve added a couple of photos.
Many thanks.
21 May, 2022
Answers
If you have a friend with a freshwater fish tank, or a fishpond, see if you can get some of the old water and/or goop from the bottom, next time they clean it. Apply it over the root area of the grapevine and water it in well. The fish droppings contain beneficial bacteria that help the grapevine produce the chemicals it uses to resist pests like that--and also make the grapes taste better. :)
23 May, 2022
This looks very muck like grape blister mite damage.
link to the RHS site
says it wont affect fruiting and very little in the control of it.
https://www.rhs.org.uk/biodiversity/grapevine-blister-mite
21 May, 2022