Rhododendron: Rust
categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs
last review date: 2025-06-27 09:51
Photo by: R.S. Byther
Biology
Yellowish spots on the upper leaf surface and dark brown or purple spot on the lower leaf surface can indicate the presence of a rust infection. Later, the underside develops blisters which break open to reveal characteristic yellow to orange or reddish spores.
Rusts can also affect azaleas. The disease overwinters on the host plant.
Management Options
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
Non-chemical Management
Select non-chemical management options as your first choice!
- Prune and destroy infected leaves.
- Clean up and destroy any diseased leaves that have fallen to the ground.
Chemical Management
IMPORTANT: For more information on using pesticides, visit Home and Garden Fact Sheets | Pesticide Resources and Education Program | Washington State University.
- None recommended
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Evidence of noncompliance may be reported through your local Extension office.