Lily leaves have yellow and brown on them
Thank you for the question. The three diseases that can be problematic for lilies are lily mosaic, Botrytis blight, and basal rot. Lily mosaic, a virus disease spread by aphids, usually produces streaking or mottling of the leaves, followed by distortion. Affected plants produce few flowers, and they may be deformed, or buds may fail to open properly. Plants affected by this should be dug up and discarded. Botrytis blight is a fungal disease that begins on lower leaves and ascends the stem. Orange-brown spots spread and merge together, and spores form a gray mold. If it infects the flowers, a messy decay results. Although wet weather is conducive to the development of fungal diseases, many factors affect the extent and severity of infection from year to year. Basal rot, also caused by a fungus, can be serious, infecting both roots and bulb. Fortunately, hybrids and species vary in their susceptibility to this disease. Infected lilies simply disappear or plants may emerge later in spring, growth is stunted, and foliage may yellow and die prematurely.
Judging from the picture you sent, Botrytis blight seems a likely candidate. The following two sites will provide additional information
I thank you very much.
I pulled off the discolored leaves from different sets of lilies. Should I keep these lilies growing or should I discard them? Is the lily itself still healthy once it has had these discolored leaves? Do my lilies need more space from each other to optimize their health?
Thanks again. May you have a wonderful day.
After removing the discolored leaves, I would put these into a plastic bag that should be put into the trash. Do not compost them. It is hard to tell at this time what will happen to the rest of your plants. I would be hesitant to move the plants at this time. Your lilies may already be stressed by being exposed to this fungus. Be sure they are well watered. Keep an eye out for further infected leaves. If none appear then you have caught things in time. If eventually the entire plant is affected, you should contact us again regarding steps to be taken to prevent things from recurring in 2019.