PlantLife Online

Answer

It sounds like your Hollyhock has rust. Rust is a fungus which affects the surface of the leaves developing yellow spots. Another symptom is the orange brown pustules on the undersides of the leaves and may also form on the upper side of the leaves, stems, and green flower parts. Hollyhock rust tends to become more severe as the summer progresses, killing most of the leaves on infected plants by early fall. The best method of control is to break the disease cycle, cut all hollyhock stalks to ground level in the fall removing and destroying all parts of the plant. The other option is to start fungicide applications as soon leaves open in the spring, if leaves become infected remove each leaf immediately. Consult your local garden center about the best fungicide formula for your location, many states have different regulations.