forgot the link to the pic... oops!

Here is a link that might be useful: spotted hydrangea

Does it come off if you water the leaves? Have you tried removing them with your hand (you may want to use gloves until you know what that is)?

Sorry. I left out the last question... do you notice movement? I was thinking that it could a form of scale (cottony maple leaf scale) that is treatable using Bayer with an active ingredient called Imidicloprid.

well, so far i haven't noticed any movement but I will take a very close look tomorrow - .. and the pics I posted were after a brisk rinse with the hose - perhaps a few came off but that's it. meanwhile, thanks for the ideas.
dory

Not scale.

I believe this thread was elsewhere. Perhaps spray damage of some sort which killed small islands of tissue. Leave the plant be. Keep all leaves.