By Wendy Diaz, NC State Extension Master GardenerSM volunteer of Durham County
Evidence of Cedar-Quince Rust on Eastern Redcedar (Juniperus virginiana)
I noticed a bright orange coating on the peeling bark of the branches and trunk of an Eastern Redcedar shrub (Juniperus virginiana) along my backyard property boundary during a routine walk around my yard in the early spring last year.
Orange swellings between peeling and on bark of Eastern Redcedar branch on March 13, 2025. (Image credit: Wendy Diaz)
Many years ago, I transplanted it along with several other volunteer Eastern Redcedar seedlings, to create a windbreak and evergreen screen when the hardwood forest behind our property was developed into a subdivision. I knew at the time it wasn’t an ideal location for these sun-loving natives[1]; under the shade of a large White Oak but they did survive and slowly grew from 4 inches to several feet high.
View of backyard Eastern Redcedar hedge. Area circled in red denotes the diseased cedar shrub planted behind the white oak tree which was diseased and later removed. (Image credit: Wendy Diaz)
The Eastern Redcedar with the orange coating was located in the most-shaded part of the hedge and behind the oak, so it was no surprise to me that it developed a disease at this location. There are three different rust fungus that can infect Eastern Redcedar: 1. Gymnosporangium juniperi-virginianae[2] which produces bright orange gelatinous galls with tendril-like protrusions or Cedar-Apple Rust (spores from these galls will infect apple trees). 2. Gymnosporangium globosum smaller, less conspicuous branch galls, with horn-like protrusions or Hawthorne Rust and, 3. Gymnosporangium clavipes or Quince rust (spores infect rosaceae plants). I did not observe round branch galls[3] so I concluded Cedar-Quince rust was the disease on my cedar shrub which is caused by the Gymnosporangium globosum fungus[4].
Close up of Cedar-Quince Rust on branch of Eastern Redcedar on March 13, 2025. (Image credit: Wendy Diaz)
Disease Cycle
These fungi need plants from two plant families to complete their life cycle (multiple hosts).[5] Of the rust diseases, Cedar-Quince has the broadest host range and affects many genera of the Rosaceae family including apple, crabapple, flowering quince, hawthorn, serviceberry and mountain ash.[6] In damp spring weather it forms orange, gelatinous blisters on the bark of branches of the Eastern Redcedar. It can kill young branches and weaken plants when the cankers develop on the main trunk. When it infects the other hosts, like apple, it infects the young branches and fruit but not the leaves. Basidiospores released from the Eastern Redcedar branch orange swellings will infect the stems and fruit of quince and other deciduous host plants. Seven to ten days after infection spots develop, followed by the formation of tiny black dots within the spots a few days later. Globular or cup-shaped structures (aecia) are formed four to seven weeks later. Aecipospores, which are released during a rain event from these structures, will become airborne and infect susceptible Easter Redcedar plants during late summer or fall. One year later, swellings composed of both fungal and host plant tissues will develop on the Eastern Redcedar host. When the spring weather is wet and cool (74 to 78 degrees F) swelling on the branches of the Eastern Redcedar will result in the release of basidiospores which in turn will infect quince or another deciduous host, and the cycle continues.
Management of Cedar-Quince Rust on Eastern Redcedar
Pruning and proper disposal of the infected branches, if practical, is a good way to control the disease. I decided to remove the thinly branched Eastern Redcedar and burn it because it had lost it ornamental value and it was unhealthy and the other cedars beside it did not appear to be infected. Because two kinds of plants are necessary for the survival of this fungus, removal of my old flowering quince in my front yard that has developed galls seems to be a practical solution for me because I want to eventually remove most of my non-native species in my yard.[7]
There are preventive fungicides that are made to protect developing/new growth twigs and branches from infection during the time the swellings on the Eastern Redcedar are orange and gelatinous. Multiple applications over several weeks are necessary until the orange coating becomes dry and inactive. Pesticides registered for use include: captan, chlorothalonil, mancozeb, sulfur, thiram and ziram. Other strategies include not planting susceptible host plants within a few hundred yards of apples, hawthorns and other plants of the Rosaceae family. Other cultural methods of disease control would be planting plants that are resistant to rust diseases and removing galls from the deciduous host plants to reduce infection of the alternate host plant. The gall is not as big as the black knot disease[8].
Black gall on the flowering quince on Febraury 24, 2025. The gall is not as big as those associated with black knot disease.8 (Image credit: Wendy Diaz)
This experience was a reminder to me to take a stroll and inspect parts of my yard that I have taken for granted and it was well worth the time because the other adjacent Eastern Redcedar shrubs in my border screen do not exhibit any fungal rust symptoms. Scouting for disease is good gardening practice. You know what they say ‘an ounce of prevention is worth a pound of cure’. If you have Eastern Redcedar trees in your yard now is the time to inspect for any evidence of fungal rust disease. Your neighbor with a flowering crabapple may thank you.
Notes
[1] https://plants.ces.ncsu.edu/plants/juniperus-virginiana/
[2] https://hgic.clemson.edu/factsheet/juniper-diseases-insect-pests/
[3] https://content.ces.ncsu.edu/extension-gardener-handbook/5-diseases-and-disorders#section_heading_7616
[4] tps://ask2.extension.org/kb/faq.php?id=828832
[5] https://hgic.clemson.edu/factsheet/cedar-apple-rust/
[6] https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/insects-pests-and-problems/diseases/rusts/cedar-quince-rust
[7] https://extension.umn.edu/plant-diseases/cedar-apple-rust
[8] https://hyg.ipm.illinois.edu/pastpest/200715b.html
Resources and Additional Information
Read about another fungal disease that affects trees (Black Knot Disease: Apiosporina morbosa ) in a previous post by Melinda Heigel: https://durhammastergardeners.com/wp-admin/post.php?post=15569&action=edit
The links highlighted in the notes are excellent resources for learning more about fungal rust that can infect the Eastern Redcedar.
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