🍄Fungal diseasesModerate
Rust
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When it strikes
Temperature
10–24°C
Humidity
≥85%
Leaf wetness
Required
Season
Spring, Summer, Autumn
About
Rust fungi are a large group infecting beans, hollyhock, roses, daylilies, cereals and many plants, recognisable by powdery orange pustules and favoured by humid weather with cool nights.
Symptoms
Yellow, orange, or rusty-brown powdery pustules on leaf undersides with yellow speckling above; severe infection causes leaf drop and weakened plants.
Organic Treatment
Remove and bag infected leaves, improve airflow, and apply sulfur or a Bacillus-based biofungicide. Avoid overhead watering.
Chemical Treatment
Myclobutanil, tebuconazole or mancozeb every 10–14 days during humid weather.
Prevention
Plant resistant cultivars, space for airflow, water at the base, and remove plant debris where rust overwinters.