Onion white rot

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Onion white rot
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A garlic bulb showing symptoms of onion white rot
Scientific Classification
Kingdom: Fungi
Phylum: Basidiomycota
Subphylum: Agaricomycotina
Class: Agaricomycetes
Subclass: Agaricomycetidae
Order: Agaricales
Family: Typhulaceae
Genus: Sclerotium
Species: Sclerotium cepivorum

Onion white rot, allium root rot or mouldy nose is caused by the pathogen sclerotium cepivorum that destroys the roots, killing the plant. It then produces resting bodies that can last for many years in the soil.[1]

Identifying Features[edit | edit source]

Leaves wilt and turn yellow. In wet conditions the plant may not wilt, but can become loose in the soil. When plants are lifted; white fluffy growth can be found on the base. In advanced cases, you will see black, pinhead-sized, regular spheres. These are the sclerotia, or resting bodies, that will carry the disease from one crop to the next.[1]

Onion white rot appears similar to onion fly or bean-seed fly, but also shows a white mould. These pests tend to go for onions rather than other alliums.[1]

Treatment[edit | edit source]

Remove and destroy affected plants and a few inches of surrounding soil.[1] Do not grow other alliums on the same site for another 8 years. This fungus survives in the soil for a very long time. There is currently no chemical control.

Garlic spray[edit | edit source]

It is currently being investigated whether spraying the intended growing site with garlic spray two to three weeks before sowing alliums will reduce a white rot infection. The theory is that the garlic releases sclerotium spores into action, but as there are no plants on which to feed, the spores die.[2]

Prevention[edit | edit source]

Practising crop rotation will help leave sufficient time between allium crops to reduce sclerotia in lightly infected soil, but will do little to prevent infection in a heavily infected site.[1]

Hosts[edit | edit source]

Potential pathogen hosts include:

References[edit | edit source]

  1. a b c d e (2009). Onion white rot. Which. GWF336
  2. Jones, A. (2010). Onion White Rot. Grow Your Own Magazine - The Grapevine Forum. Retrieved 2010-07-22.