Answer: Rust can spread from plant to plant and in my experience it seems to be in every garden to some extent, so we can only hope to reduce the reinfection rate. I am not aware of any soil treatment. The best things to do are to clean up, remove and destroy all infected plant debris (burn it or put it in the trash, not in the compost) as it happens and at the end of the season; plant susceptible plants in locations with good air circulation; and avoid watering the foliage or otherwise wetting it unnecessarily. Finally, cut the plants back after blooming. If the rust is still intolerable, you might consider a fungicide containing sulphur applied according to the label instructions.
Hollyhocks are notorious for rust infections and since it is so difficult to control many gardeners will plant them in an out of the way spot or at a distance so that the rust is simply less noticeable. Hollyhocks are also usually treated as biennials, meaning they grow for a year and winter over, then bloom the second summer, then set seed and die. It may be that your hollyhocks were simply following their natural schedule rather than killed by the rust.
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