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Rust Disease

A fungal disease producing orange, yellow, or brown pustules on leaves and stems. Rust is highly contagious between plants of the same species.

Symptoms

  • check_circleBright orange, yellow, or brown powdery pustules on leaf undersides
  • check_circleYellow or pale spots on the upper leaf surface above pustules
  • check_circleLeaves yellowing and dropping prematurely
  • check_circlePustules releasing orange spore clouds when disturbed

Causes

  • arrow_rightFungal spores spread by wind, water splash, or insects
  • arrow_rightHigh humidity and moderate temperatures (15–25°C)
  • arrow_rightDense planting reducing air circulation
  • arrow_rightOverhead watering keeping foliage wet

How to Diagnose

The orange, powdery pustules on leaf undersides are distinctive. Different rust species affect different plants — they are not transferable between unrelated species.

Treatment

Remove and destroy all infected leaves. Do not compost them. Apply a sulphur-based or copper fungicide. Improve air circulation. Avoid wetting foliage.

Prevention

Space plants well. Water at the base. Clear plant debris at end of season. Choose rust-resistant varieties. Apply preventive fungicide sprays in high-risk periods.