- Cucumber mosaic virus is a common problem with lily growing. It causes brittle, discolored leaves and flowers. It can even stunt the growth of a flower. This virus can live through winter in the leaves of perennials and infect the new growth in the spring. Viral diseases infect the entire plant--flower, leaf, roots and stem--and so any bulbs that you get from an infected plant also will be infected but the seeds will not. This disease will not withstand drying of the soil.
- Basal rot is a form of fungus. Fungi live on plant tissue and feed from the nutrients in the plant, eventually starving and smothering it. One type of this fungus can live in soil for three years without a host, then infect any new plant that begins to grow there. This fungus is recognized by a dark brown rot that begins at the basal plate, or the base of any stem on a plant. From there it spreads throughout the entire lily.
- This virus is the most common virus associated with growing lilies. As its name suggests, this virus doesn't have recognizable symptoms and often never shows any symptoms. It will, however, cause damage and weaken the plant. It will make the lily more vulnerable to other disease and viruses.
- The biggest problem with lilies and insects is aphids. Surprisingly, aphids are a particular problem with potted lilies, probably because there aren't as many ladybugs inside. Ladybugs eat aphids and naturally reduce aphid populations.
Aphids feed on plant material and can cause holes but this isn't the only problem. Aphids carry viruses from one flower to the other. If ladybugs are not available, there are multiple products on the market targeted at reducing aphid populations. - Botrytis is another type of fungus that attacks lilies. It affects the surfaces of the plant and will spread fast to neighboring plants and flowers. The Pacific Northwest is referred to as a "botrytis climate" because the moisture is a perfect habitat for the fungus.
White dots on the leaves can be a sign that botrytis is beginning to devour your lilies. If left untreated, the entire leaf will eventually shrivel. Keep the leaves dry; a fan is helpful for drying indoor plants. When watering, only water the soil and try to keep the foliage and flowers dry.