What is this on underside of leaf?

[jrg]

We have some grapes growing on our entrance way arch and I noticed this the other day.
see picture.
Not many leaves as of yet.
Thanks
James

 

[balatonwine]

If the top side of the spots are raised, it is erineum leaf mites.

https://pnwhandbooks.org/insect/small-fruit/grape/grape-grape-erineum-mite

 

[VinesnBines]

Looks like downy mildew and it will spread.

 

[jrg]

The top is raised.
Time to break out the safer's soap.