Rust (fungal leaf rust)
DISEASE
When it's active · UK
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When it's active · Northern Italy
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When it's active · Central Italy
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When it's active · Southern Italy and islands
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How to recognise it
Small orange, brown or yellow pustules, usually on the leaf underside, releasing a dusty spore mass if disturbed.
Life cycle and conditions
A large group of related but plant-specific fungi (rose rust, mint rust, allium rust, hollyhock rust among others); favoured by humid conditions and overcrowded planting.
Prevention
Improve airflow, avoid overhead watering, remove fallen affected leaves promptly.
How to treat it
🌿 ORGANIC · RECOMMENDED
Remove and dispose of infected leaves promptly and improve airflow — cultural control is usually sufficient at garden scale for this disease.
🧪 CHEMICAL · IF YOU CHOOSE
A general-purpose fungicide approved for amateur use can help on a particularly valuable plant if applied early, as a last resort alongside the bio-friendly approach, not instead of it.
PLANTS MOST AFFECTED
IN THE CARE SHEETS
Hardy geranium