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Botrytis squamosa (teleomorph: Botryotinia squamosa) is a fungus that causes leaf blight on onion (often termed ‘blast’) that is distinctly characterized by the two stages – leaf spotting followed by blighting. [1] The pathogen is an ascomycete that belongs to the family Sclerotiniaceae in the order Helotiales. [2]
Stemphylium solani is of greatest concern in tomatoes, potatoes, peppers, garlic, onions, and cotton, though a wide range of over 20 species have proven susceptible. In tomatoes and potatoes, the resulting disease is known as grey leaf spot. In alliums it is known as leaf blight. Additional hosts are listed below. [1] Onion, Allium ascalonicum
P. destructor causes a wide range of symptoms in onions. From afar, downy mildew of onions can be detected by patches of yellowed plants incapable of growing to the size of surrounding healthy plants. Leaves: When looking at individual leaves, necrotic spots begin as yellowing spots that eventually turn brown or black as the leaf tissue dies. [5]
This mycelial layer may quickly spread to cover all of the leaves. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.
Leaf spots can vary in size, shape, and color depending on the age and type of the cause or pathogen. Plants, shrubs and trees are weakened by the spots on the leaves as they reduce available foliar space for photosynthesis. Other forms of leaf spot diseases include leaf rust, downy mildew and blights. [4]
5. Low Humidity. Light brown spots scattered across fiddle leaf fig leaves can be caused by dry air. If the brown spots in question have a pox-like look instead of being in a single area of the ...
Stromatinia cepivora is a fungus in the division Ascomycota.It is the teleomorph of Sclerotium cepivorum, the cause of white rot in onions, garlic, and leeks. [2] The infective sclerotia remain viable in the soil for many years and are stimulated to germinate by the presence of a susceptible crop.
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