Cedar-quince rust

Cedar-quince rust is closely related to cedar-apple rust -- both are caused by Gymnosporangium species and require Eastern red cedar as an alternate host -- but the two diseases differ in which parts of the host plant they attack. Cedar-apple rust primarily attacks leaves; cedar-quince rust attacks.

Cedar-quince rust is closely related to cedar-apple rust — both are caused by Gymnosporangium species and require Eastern red cedar as an alternate host — but the two diseases differ in which parts of the host plant they attack. Cedar-apple rust primarily attacks leaves; cedar-quince rust attacks fruit, stems, and thorns. This shift in target tissue makes cedar-quince rust more economically significant for fruit production: infected fruit is unsalable, and infected stems may die back.

I don't grow quince or commercial apples at my Long Island property, so this guide draws on Penn State Extension, Clemson HGIC, and Cornell research.

The pathogen

Cedar-quince rust is caused by Gymnosporangium clavipes. Per Penn State Extension, this species has a broader host range on the rosaceous hosts (the apple family) than G. juniperi-virginianae. Hosts susceptible to cedar-quince rust include:

• Quince (Cydonia oblonga)
• Hawthorn (Crataegus spp.)
• Serviceberry (Amelanchier spp.)
• Apple and crabapple (Malus spp.) — primarily fruit, stems, and petioles rather than leaf blades
• Pear (Pyrus spp.) — less commonly

The alternate host is Eastern red cedar and other junipers (Juniperus spp.), particularly Juniperus virginiana.