Stemphylium blight
Crop: Onion Disease: Fungal Pathogen: Stemphylium vesicarium
SYMPTOMS AND SIGNS
DISEASE DEVELOPMENT
DISEASE MANAGEMENT
- Since this fungus is usually found co-infecting with Alternaria porri, symptoms are identical or at least very similar to purple blotch. However, Stemphylium leaf blight lesions appear to be a darker, more olive-brown to black color than do purple blotch lesions. Lesions are often more numerous on the sides of onion leaves facing the prevailing wind.
- The centers of lesions turn brown to tan, then dark olive brown and finally black as the fungus sporulates.
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An attack begins with small, light yellow to brown, watery spots. After a while these develop into elongated blotches that can merge with each other and attack the entire leaf. The blotches are light brown in the middle, becoming darker towardsthe edges. Black fruiting bodies can be seen clearly.
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Dark spots on the ends of dying stems can be seen. The leaves and leaf sheaths are small, light yellow to brown, and water-soaked. As the lesions expand they coalesce causing extensive blighting of the leaves.
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Initial infections on the leaves and leaf sheaths are small, light yellow to brown, and water-soaked. As the lesions expand they coalesce causing extensive blighting of the leaves.
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Initially small, light yellow to brown, watery spots appears on the affected leaves which later on develops into elongated blotches that can merge with each other and attack the entire leaf. The blotches are light brown in the middle, becoming darker towards the edges. Black fruiting bodies can be seen clearly.