Daffodils suffer from a number of diseases. White mould, caused by Ramularia vallisumbrosae, can be a problem for daffodil growers in the South-west of England. It was first found in East England in 2001. The disease occurs occasionally on campus.
Symptoms are yellowed areas on leaves which become brown in the center. Early in the infection white mould can appear on the yellowed areas. These branched hyphae bud off small spores that can infect other leaves.
Later, on the dead, brown areas in the centre of the infection site, tiny black spots appear. These are sclerotia. They are specialized over-wintering structures which can remain in the leaf litter on the ground when the daffodils become dormant. When environmental conditions are right, the sclerotia produce spores that infect fresh leaves in the spring.
O’Neill, T. M., Hanks, G. R. & Kennedy, R. (2002) First report of white mould on daffodils in Eastern England. New Disease Reports 4: 19