Pathogen Information
Alernaria Leaf spot is caused by one of three species of fungal pathogens A. brassicicola, A. brassicae, and A. raphani.
- Dark brown to black circular lesions with target-like rings
- Yellow halos surrounding the spots
- Spots that can merge as disease progresses
- Can affect leaves, stems, and fruits
Environmental Conditions
- Temperature: 60-80°F
- Humidity: 90%+
- Most effected species: Amaranthaceae, Brassicaceae, and Solanaceous
Disease Progression
Early Stage
Small, dark brown spots appear on leaves
Mid Stage
Spots enlarge, develop concentric rings
Late Stage
Leaves yellow and die, spots merge, defoliation occurs
Prevention Methods
- Avoid overhead irrigation
- Maintain proper plant spacing
- Remove and destroy infected plant debris
- Use disease-free seeds and resistant varieties
- Rotate crops with non-susceptible plants
- Keep leaves dry and improve air circulation
Treatment Options
- Azoxystrobin fungicides
- Chlorothalonil-based fungicides
- Neem oil treatments
- Copper-based fungicides
