As rust is such a common problem for hollyhocks, it is useful to know how to treat it if you identify it. You should keep an eye on your hollyhocks if they are prone to getting rust. The moment you spot the telltale yellow spots, remove the affected leaves to prevent the fungus from spreading. If removing the affected leaves is not enough to kill the infection, you can try applying a fungicide. Indeed, you should probably follow up with that step even if the infection appears to be gone.