• Root rot (Pythium sp.): Roots become softened and have a brown discoloration. Particularly likely to occur in poorly drained mixes.
• Root rot (Rhizoctonia sp.): Roots show a brown discoloration and may appear stunted. May be present in addition to Pythium.
• Virus (mottle, streak): Foliage shows pale streaking or spotting; flowers may be distorted or small. Rogue out infected plants; control aphids (potential vectors). CMV and potyvirus have been found in symptomatic lilies in recent years.
• Leaf scorch (physiological): Seen primarily in Croft lilies; tip scorch on leaves. Keep calcium levels and pH high (use a pH of 6.8 to 7.2) and avoid sources of fluoride such as superphosphate and perlite.
• Upper leaf necrosis (physiological): Seen primarily in the hybrid lily ‘Star Gazer,’ this appears as dead areas in the leaves just below the flower. The cause of this problem has been determined to be a calcium deficiency that occurs most often with larger bulbs. Research is under way to devise methods for correcting the problem. Keep plants well ventilated to encourage transpiration.