Leaf Scorch or Red Blotch (fungus – Stagonospora curtisii): Flower stalks are affected resulting in their being distorted and stunted. Affected stalks have bright red lesions that are one-fourth to one-half inches wide and several inches long. Affected flower stalks grow at an angle instead of the normal erect manner. In the later stages of infection, a white to brownish-gray mycelium develops in the center of cankers. The fungus is carried over in bulbs and discolored bulbs should be discarded. Foliar fungicides may be used to protect above-ground parts.
Bulb Rots (fungi – Botrytis spp., Rhizopus spp., Sclerotinia spp., Pythium spp. and others): Bulb rots caused by fungi are quite common. The fungi may enter the outer scales and progress inward until all scales are infected. Bulbs showing signs of infection should be discarded to prevent contamination of the beds. Soil sterilization with chemicals or with steam may also be helpful.
Mosaic (virus): Infected plants are stunted and have yellow mottled leaves. The mottle becomes more severe with stunting of all plant parts as time progresses. There is no chemical control and once a plant becomes infected it will remain that way throughout its life. Infected plants should be destroyed.
Southern Blight (fungus – Sclerotium rolfsii): A white fungal growth appears at the ground line and infects the plant at that point. Damage results in death of the above-ground portions. Small bead-like structures (sclerotia) appear among the white fungal strands and serve as overwintering bodies for the fungus. A drench with a soil fungicide is usually sufficient to correct the problem. Avoid the accumulation of plant residue around the plant base.