I've noticed some plants get rust quickly but can also recovery quickly.
Some resistant plants with #1 rating can hold off rust for a long time,
but when they show it are almost overcome by it and take longer to recover.
Garden location matters -- early morning sun, air circulation, temperature, humidity, etc.,
as does fertilization and soil mineralization, how long the plants have been in place
and haven't been divided since moving seems to weaken them.
Some plants attract every rust spore passing by no matter what.
If rusty leaves touch a resistant plant long enough, the resistant plant will eventually get rust.
There's more on "vertical" and "horizontal" here:
http://daylilybreeder.blogspot...
