I think what you have is smut. Check out this link.
http://plantpathology.tamu.edu/Texla...s/Corn/cs.html
I think this is what you described. I've seen it growing on the ear itself, on the tassel, but mostly down low, around the root. It is most severe during dry weather. I don't know any cure for it, or have any suggestions what to do. Sorry.