Mallow Rust

Puccinia malvacearum, also known as hollyhock or mallow rust, is a fungal species within the genus Puccinia known for attacking members of the family Malvaceae. An autoecious pathogen, it can complete its life cycle using a single host.

It was originally found on the leaves of a species of Malva in Chile.
Other plants also affected by the rust include Abutilon, Alcea (Hollyhock), Hibiscus, Lavatera, Malvastrum and Sphaeralcea.

Suggested control measures (in the US), include sanitation (removal or destruction of affected plants or plant portions) or treatment with fungicides.