Okay... I just found this line: (7) Destroy volunteer overwintering plants and avoid planting near established diseased crops. from the following site: http://plantpathology.tamu.edu/Texlab/Multicrop/asteryellows.html Does a volunteer overwintering plant mean from seed too or just from a from a plant that survived the winter? I wonder if the warning for not planting new plants near currently infected plants only means during the same season, or if it also includes a new growing season where once infect plants once were. The only spaces in my garden for the new coneflowers are where the diseased were pulled up. :c( Should I not even bother?

it would be nice to see a picture of the top surfaces of the leaves as well as the bottom. But just based on what you have plus that little bit of the top surface showing on the leaf in the middle, I think I can narrow it down to two(?) diseases. Either basil late blight or basil downy mildew, which are likely two names for the same thing... Not to be confused with late blight of tomato, an entirely different disease This post was edited by nickl on Wed, Aug 28, 13 at 15:25

Those very tightly clustered burgundy leaves are bothersome to me -- it reminds me of those bunches of leaves poking through where blooms should be, when a plant is afflicted with Aster Yellows. Oh, man, starting to feel very unlucky. I just remembered last year, a passionvine (that crept underneath the fence from our neighbor) became infected with what was most likely cucumber mosaic virus; the leaves had all the right symptoms. So, I carefully yanked as many leaves as I could and disposed of them properly. I had a couple of buddleia davidii planted in the same spot where the mistflowers are now, and they both showed signs of CMV infection. If it's still in the ground/roots of the buddleia, it may have infected the mistflowers. How long does this stuff hang around? I have two gorgeous Amistad salvia, and I'm worried about them now. I've got P. foetida growing on a trellis directly behind the mistflower patch -- see the leaves? I'm still not familiar with the natural habit of these plants, and assumed these older leaves were just, what, on their way out...? Are we possibly looking at CMV now? If so, I'd appreciate help with a remedy for this area. TIA.

Ah, Heterotheca subaxillaris (Camphorweed) confirmed by its mentholy aroma when rubbing its sticky leaves...thanks!