Onion basal rot
As Zwiebelbasalfäule refers to a plant disease that mainly daffodils attacks. It is caused by the fungus Fusarium bubigenum .
The spores of the fungus settle in the onion skins. During the storage of the bulbs, they can multiply easily, especially if daffodil bulbs are stored too warm. In the case of planted daffodils, the fungal attack causes the leaves to turn yellow well before the normal time and then die. The flower can then no longer develop. In heavily infested plants, onion basal rot leads to complete rotting of the cork-like onion soil.
The disease poses a problem for both commercial and private gardeners worldwide, as the fungus remains in the soil for several years. Places where plants contaminated with the fungus stood should therefore not be planted with daffodils for at least five years.
Treating the disease is through careful handling of the onions. Injured onions should be sorted out. The onions are pickled to prevent fungal attack, and in some nurseries they are also treated with hot water. Mineral fertilizers with a high potash content reduce the infestation.
However, there are some resistant types of daffodils. These include the species and the cultivars of the Jonquillen , Angel's Tear Daffodils and Tazettes that come from them .