Hollyhock Rust Fungus
Although hearty plants, Hollyhocks are prone to rust disease. A serious rust outbreak during the nineteenth century temporarily caused hollyhocks to lose popularity with the British. Rust infection generally does not cause death of the plant, but does stunt growth and cause discoloration and premature shedding of leaves. These parasitic fungi first appear on the underside of a leaf in small blister-like formations that are reddish-brown in color. On the opposite side of the leaf, the blisters appear as larger bright yellow to orange colored spots. The Autoecious rusts complete their entire life cycle on one host and can attack all green parts of the Hollyhock plant.