Apple Scab or Red Cedar Rust - Ask Extension
Can you help identify what disease our apple trees have? Thank you.
Knowledgebase
Apple Scab or Red Cedar Rust #402803
Asked May 27, 2017, 1:13 PM EDT
Can you help identify what disease our apple trees have? Thank you.
Carver County Minnesota
Expert Response
It looks like apple scab. The lesions in cedar-apple rust are large and bright orange. Also, you should find the fruiting body of the fungus on a nearby cedar. Read here:
https://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/apple-scab/
https://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/cedar-apple-rust/
Compare photos. Cedar apple rust:
http://extension.missouri.edu/adair/cedarapplerust.aspx
Apple scab:
https://www.treecarescience.com/tree-problems/apple-scab-diagnostic-guide/
However, it is hard to identify a disease on the basis of a photograph of a single leaf. Apple scab looks different at different stages, so a sampling reflecting the spectrum of infection would be more useful. Apple scab is the most common disease of apples in Minnesota, but not the only disease.
https://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/apple-scab/
https://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/cedar-apple-rust/
Compare photos. Cedar apple rust:
http://extension.missouri.edu/adair/cedarapplerust.aspx
Apple scab:
https://www.treecarescience.com/tree-problems/apple-scab-diagnostic-guide/
However, it is hard to identify a disease on the basis of a photograph of a single leaf. Apple scab looks different at different stages, so a sampling reflecting the spectrum of infection would be more useful. Apple scab is the most common disease of apples in Minnesota, but not the only disease.
