My first reaction was like Dirt's....."Yikes!"
Rust is my nemesis, especially for my hollyhocks.
But I found that if I give them Bayer 4-in-One early
before it is visible, they get very green & buff, and
it prevents the rust.
Thanks, though for the all the info, pics, & links by Baja, et al.
Now I'm going to take a shower.