White rot: Yellowing and dieback of leaf tips
Pathogen: Sclerotium cepivorum
Symptoms
Leaves become yellow and wither. The initial symptoms are yellowing and dieback of leaf tips. Later, scales stem plate and roots get destroyed.
Disease development
White rot fungus can stay in the soil on plant debris or as sclerotia. The sclerotia can remain dormant in the soil for many years germinating as soon as onions or a related crop are cultivated on the land again. White rot can spread quickly from root to root. Cultivation machinery, planting material, crates or footwear can also spread the disease.
Disease management
Avoiding infection is essential. Follow good hygiene protocols on the farm. Avoid soil from infected plots being carried by machines to other plots. Correctly registering infected plots can prevent it from spreading to uninfected plots. Inspect the propagating material (for example onion sets) for the presence of white rot. If the disease is detected for the first time in a certain plot, remove and destroy as many infected plants as possible to prevent the rapid spread of the infection. Inundating or solarising (in subtropical regions) infected areas or entire plots can reduce the number of sclerotia.
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