Can anybody help me to identify a disease that I've just noticed this week attacking my table grapes for the first time? It seems to be spreading fast. So far, I've removed any affected leaves. But that is starting to add up. I'd like to spray and knock it down.

It is a mustard yellow fungus that appears on the underside of leaves in small spots and then grows quickly to cover a wide area. On the upper side, the infection causes the leaf to become dark brown and scorched. Seemingly within a few days the leaf begins to curl upward, harden, and close. Affected leaves are usually near each other, but not always on the same stalks. The worst hit are my Canadice, followed by my Vanessa grapes. The Steuben is only little affected.

The Canadice and Vanessa appear to have a problem with Phomopsis this year as well, but I don't believe that's the cause of this. I've looked at photos of angular leaf scorch, but it doesn't appear to be that disease either.

I've been spraying every 10 - 15 days since June 7 with fixed copper or Pristine. I missed the young-shoot sprays, though. The usual diseases are under control this summer: black rot is pretty well knocked down by now, and powdery mildew hasn't appeared yet. I last sprayed with copper a week ago. We've had several rains since then, and generally moisture or high humidity at night.