Can you identify this aggressive foliar disease?

[Eric02476]

I'm stumped. Does't look or act like Alternaria or Early Blight but I've never had significant disease problems with potatoes so I am much less familiar with what they look like on this crop. Fungal, bacterial, or viral? And is there any point to spraying?

I grew all King Harry this year because of heavy losses from potato leafhopper the past 2 seasons. Well, I haven't noticed leafhoppers or hopperburn damage, but this disease started about a week ago, slowly, and in the past 2 days it's rampaging. First there's yellowing and specks, then browning of the veins, and then the leaf starts to die. Ugly.

I did spray Daconil 2 days ago when it became clear this was more than a nuisance but I know that's too late. I have Copper, BioSafe and potassium bicarb sprays on hand if you think it would do any good. But the main question is whether this is something so virulent that it threatens my tomatoes, which are in noncontiguous beds about 10-15 feet away. Hate to sacrifice the potato crop now but if they're goners anyway, maybe I will.

Eric