symptoms
Symptoms
- circleSmall circular spots with grey-tan centres and dark purple-brown borders
- circleSpots appearing first on older, lower leaves
- circleYellow halo surrounding mature spots
- circleLeaves yellowing and dropping prematurely in severe infections
help
Causes
Caused by the fungus Cercospora, which thrives in warm, humid conditions (25–30°C) with extended leaf wetness. Spreads via wind-blown spores and water splash from infected plant debris left in the soil over winter.
healing
Treatment
Remove and destroy infected leaves immediately — do not compost them. Apply a copper-based or chlorothalonil fungicide at first sign of symptoms, repeating every 7–10 days during humid weather. Improve air circulation by thinning crowded plants.
shield
Prevention
Rotate crops on a 2–3 year cycle to prevent spore build-up in soil. Water at the base rather than overhead. Space plants for good air flow. Clear all plant debris at the end of the season. Choose resistant varieties where available.