See:
Iris, Bulbous and Rhizomatous (Iris spp.) - Crown Rot
Cause Sclerotium delphinii, a fungus that can survive as sclerotia for several years in soil. Infection usually is on the stems near the soil surface. Disease development and spread can occur very rapidly under mild to warm, moist conditions in the field or in storage after digging. The disease is widespread and can be serious. In the Pacific Northwest, crown rot is more common on bulbous iris, tulips and lilies than daffodils.
Symptoms The bulb surface generally is covered with a coarse white growth. Small, reddish brown fungal bodies (sclerotia) may be seen in the growth or in or between scales. Infected plants turn yellow and die prematurely. The disease may be in patches in the field.
Cultural control
- Remove and destroy all infected bulbs and plants.
- Wash equipment and machinery between fields.
- Do not plant daffodils in infested soil for at least 3 years.
- Reduce planting densities.
- Early digging before the warm temperatures of summer and rapid drying of harvested bulbs has been helpful.
Chemical control
- Terraclor 400 at 3 pints/3.2 gal water. Before planting, soak bulbs for 5 min. Add 1% sticker and maintain good agitation. Group 14 fungicide. 12-hr reentry.
Reference Chastagner, G.A. and Miller, T.W. 2011. Research on ornamental bulb crops in the Pacific Northwest (2). Daffodil, Snowdrop and Tulip Yearbook 2011:30-33.