About 80% of my comfrey plants have rust. Is there anything I can do?
I've never seen rust on comfrey... :o
Apparently it's the only serious disease to infect comfrey :( and I've got it bad ;D.
what about cutting it very short?
You mean underside of the leaves are bit coppery colour? I've got some this year too..don't worry about..it comes and goes..;)
I suspect it is weather related...I've never actually looked into into it..what it is and called, propably because I haven't noticed any harm done by it or negative effect.