Plant guide:🌱 Mint
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⚠ CriticalBright orange pustules on the leaf underside � mint rust, which overwinters in the plant's rhizomes.
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Fungal
Mint Rust � Orange Pustules on Leaves and Stems
Commonly affects: Mentha spicata, Mentha piperita (Mint)
Small, bright orange, powdery pustules appear on the underside of leaves and along stems, typically emerging in spring from overwintering rhizomes. Severely affected shoots become distorted, and heavily infected plants can defoliate.
Potential Causes
- 1Puccinia menthae fungus, which overwinters in mint's underground rhizomes
- 2Wet, humid spring conditions that favour spore germination
- 3Reusing infected planting stock or soil from a previously affected patch
Solution Steps
- 1Cut back and destroy all affected top growth as soon as symptoms appear, rather than composting it.
- 2In severe cases, cut the entire patch down to the ground and destroy the debris to reduce the fungal reservoir.
- 3Avoid overhead watering, and improve airflow around the remaining patch.
- 4Consider starting a fresh patch in a new location using disease-free rhizome divisions if rust returns yearly.
Prevention Tip
Since mint rust overwinters in the rhizomes themselves, the most reliable long-term fix is starting a new patch from clean stock in a different spot rather than repeatedly treating the same infected planting.
