Frank,
You might consider trying ACTINOVATE.
It is a organic fungicide that you can get from Johnnyseeds.com
Link below:
www.johnnyseeds.com/search.aspx?SearchTerm=actinovate
On the pack description it says - Effective agains: brown patch, dollar spot, powdery mildew, grey mold, root rot, damping off, crown rot and more...
I read thru more detailed doc on it and it also says it is effective agains Alternia Blight (the biggie for Ginseng).
It is OMRI and WSDA listed.
Good Luck !
TNhunter