Alcea sp. (Hollyhock) is often
attacked by a rust disease. On hollyhock, the rust pustules are
pin head in size and may vary from yellow/red to red to brown or
gray. Severely infected leaves will die. Fungicides and sanitation
may help reduce infection. Leaf spot caused by Cerco sporella causes
angular gray to black spots (older spots may have tan centers with
brown margins). The spots may merge and tear leaving leaves with
a shredded appearance. Fungicides and sanitation helpful.
Written by James
Schuster, Extension Educator, Horticulture, and reviewed
by Bruce Paulsrud, Extension Specialist,
Plant Pathology and Phil Nixon, Extension Entomologist, University of Illinois at Urbana-Champaign.