Answer: What you describe sounds like Botrytis blight. This is the most widespread and common disease of lilies. Symptoms appear as oval or circular spots which are initially reddish-brown and develop pale centers and purplish margins. These spots may run together and rot the entire leaf,and progress into the stem and cause the stalk to fall over. If the spots dry out, they turn brown or gray. Buds or flowers may turn brown and rot and are often covered with the diagnostic gray, fuzzy growth of the fungus. This disease shows up and spreads rapidly under cool, humid conditions especially if plants are crowded.
Control involves cutting and removing any affected plant parts after the tops are killed in the fall. It is also helpful to avoid overhead irrigation and crowding of the plants. When conditions are favorable, applications of fungicides can be made when new growth emerges in the spring.
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