Summer care includes weeding, regular and deep watering. The use of fresh manure is NOT recommended. Good housekeeping means cleaning up and removing the dead foliage in the fall. Most problems associated with lilies are fungal-related, botrytis being the most common disease associated with lilies on the prairies.
Symptoms are root rot and browning of stems and leaves.
Soaking bulbs in a benlate solution prior to planting will control botrytis. Most reputable lily growers will have already done this for you. Remove only the flowering portion of the stalk, not the leaves. Like tulips and other flowering bulbs, lilies need all their stems and leaves to manufacture food for the next year's flowers. Lilies will usually thrive for years in the same spot, especially if well fertilized, but when spindly, short stems indicate crowding, the clumps should be lifted, carefully pulled apart, and the divisions planted elsewhere.