Problem-specific reference photo
under review
Problem-specific reference photo under reviewunder review
Fungal & Oomycete · Plant health field guide
Rust disease
Rust fungi form colored spore-producing structures, often on leaf undersides.
Act soonPossible cause—not a diagnosis. Compare the visible signs, plant identity, and growing conditions before treating.
Signs you may notice
- orange pustules
- brown powder
- yellow spots
Safe first checks
- Check whether orange or brown material rubs away and inspect nearby leaves.
- Separate the plant if the problem may spread.
- Remove only badly affected material with clean tools.
- Improve airflow and keep affected foliage dry while you compare the signs.
Can look similar to
Overlapping symptoms are common. Compare these alternatives before choosing a treatment.
- mineral residue
- bacterial spot
- edema
What to avoid
Do not assume every spot is infectious or use a disease-specific product without confirming the host and pattern.
Record and follow up
Photograph the same area in consistent light and note whether lesions enlarge, appear on new leaves, or stop after conditions improve.
Seek qualified local help when damage is severe, rapidly spreading, or may involve a regulated pest or disease.
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