Cedar Rust Diseases
There are several rust diseases that attack junipers. Somejunipers are more resistant than others. Cedar Apple and Cedar Hawthorn rust tend to make a roundish brown gall on the branches. After the disease finishes sporalating (orange, jelly-like telia stage) in the spring, the twig may or may not die. Quince rust looks more like a roughened but slight swollen area in the twig. The quince rust fungus tends to sporalate multiple years from these infected areas before dying.
Controls include preventive sprays, growing resistant varieties and pruning out the galls before they sporulate. For additional information on these three rust diseases as well as a chart that compares these three rusts, check the fact sheets.
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Philip L. Nixon, Extension Specialist-Entomology, Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign.
Filed under plants: Evergreen Trees & Shrubs