jerusalem artichoke choking
See photos, this is the first time in 10 years that these plants in this location have developed this....a group of these plants 50 yards away are unaffected....problem first noticed 1 week ago, spreading upward thru plants..... there have been no changes in he soil that I know of...location shaded in morning, sun in pm.
Washington County Maryland
Jerusalem artichokes like a good deal of sun and are prone to some of the same problems that sunflowers are.
It looks like you have a bit of powdery mildew and a leafspot disease called Alternaria.
It is not a huge problem and you should be fine. When edible plant parts are above ground it's much more of a problem. If and when the plant dies, simply dig up and harvest your roots.
Clean up all plant parts well at the end of the season as the disease can winter over in stalks.
Here is a page from our website on Alternaria: http://extension.umd.edu/growit/alternaria-fruit-or-pod-rot-vegetables