Unusual Growth on (Apple?) Tree Leaves - Ask Extension
I recently moved to a property with a small orchard and I noticed one of the trees has growths on the underside of the leaves. About 20% of the foliag...
Knowledgebase
Unusual Growth on (Apple?) Tree Leaves #948053
Asked November 03, 2026, 12:10 PM EST
I recently moved to a property with a small orchard and I noticed one of the trees has growths on the underside of the leaves. About 20% of the foliage is yellow / infected. These growths are small and wormlike, approx. 2-5 mm in length. When touched, they almost seem hollow like an insect casing. Photos attached are from early September.
I believe the tree is an apple, but have not seen it fruiting. There are other apple trees within 200 ft that do not have any signs of the same infection.
My best guess is this is a fungal infection, possible a type of Cedar Apple Rust.
I would appreciate help diagnosing and determining next steps for the tree.
Benton County Oregon
Expert Response
Likely that is a pear tree and you have trellis rust: https://pnwhandbooks.org/plantdisease/host-disease/pear-pyrus-spp-trellis-rust-european-pear-rust
An interesting disease that requires a cedar/juniper species host.
It may be the only pear tree on your property and that's why it is the only tree infected. We don't have cedar-apple rust that we know about in the PNW.
An interesting disease that requires a cedar/juniper species host.
It may be the only pear tree on your property and that's why it is the only tree infected. We don't have cedar-apple rust that we know about in the PNW.
