Late blight is a fungal disease that affects onion leaves, causing dark spots and plant weakness. This article from the “WORLD OF PLANTS” website provides information about the symptoms of late blight on onion leaves and methods of effective prevention and control.
Causes of late blight on onion leaves
- Disease name: Late blight of onion leaves
- Scientific name: Stemphylium vesicarium
- Type of disease: fungal
- Disease family: Pleosporaceae
Stemphylium leaf blight or late blight, where Stemphylium fungi infect onion leaves, which overwinter on plant remains and at the beginning of spring infect plants as a secondary infection with some diseases.
Symptoms of late blight on onion leaves
Brown, oval-shaped spots appear on the leaves and are soaked in water and darker during the spore formation stage. The infection can become severe and the disease can spread to the rest of the plant, where brown spots spread to the stems and fruits.
Development cycle of late blight on onion leaves
When temperatures rise in spring, ascospores are released into the air from the plant debris where the fungus lived, infecting nearby leaves that are usually infected with other diseases such as powdery mildew, insects, heat stress, or exposure to chemicals.
Suitable conditions for the spread of late blight on onion leaves
Mushrooms need moderate to warm temperatures and high humidity resulting from rainfall or irrigation, and this occurs in the spring, which is the growth season for these fungi.
Losses resulting from the spread of late blight on onion leaves
The fungus infects onion leaves, which die if the infection is neglected, leading to a decrease in the area for photosynthesis, as the fruits appear smaller and of lower quality.
Controlling late blight on onion leaves
- Chemical control: Using a fungicide containing phenhexamide, and combating powdery mildew or any disease that appears on the plant quickly to limit the spread of the disease.
- Organic control: Use neem oil in cases of insect infestation, remove the remains of infected plants and dispose of them away from the field.
Preventive measures for onion leaf death as a result of late blight
- Avoid planting onion crops for 3 years in the infected field.
- Maintain good fertilization and avoid excessive use of nitrogen.
- Maintain appropriate moisture levels in the crop.
- Use herbicides properly to avoid plant poisoning.
- Sterilize agricultural tools before use.
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Sources:
Onion Stemphylium Leaf Blight – University of Wisconsin-Madison
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