Alternaria Leaf Spot
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Alternaria leaf spot (alternaria blight, alternaria black spot) (Alternaria spp.) affects all cole-crop types. Initial symptoms on foliage are small, dark spots that later enlarge to as much as 25mm in diameter. Older lesions become tan to brown in color, often exhibiting a concentric (zonate) growth pattern and, in some cases, a yellow margin. Masses of spores may be evident in lesions under humid conditions. The centers of mature lesions may crack as the disease progresses. Symptoms, in the form of darkened lesions of cankers, are found also on stems and heads of crops such as broccoli and cauliflower.
Alternaria blight on wrapper leaves of cabbage
(Photo: UK Vegetable IPM Team, University of Kentucky)
Management
- Use pathogen-free seed.
- Fungicide seed treatments or hot-water treatment.
- Sanitation (destruction of crop residues).
- Crop rotation.
- Fungicides
