Diseased Cabernet Sauvignon leaves
Grapes are very sensitive to herbicides and this looks a bit like herbicide injury. Your best bet is to contact your extension office and see how they might process "disease" samples.
South Coast Research and Extension Center
7601 Irvine Blvd.
Irvine, CA 92618
Phone: (949) 653-1809
OK, thank you very much for the referral.