| Disease (causal agent) | Symptoms | Survival of pathogen and effect of environment | Comments on control |
|---|---|---|---|
| Botrytis blight (Botrytis elliptica, B. cinerea) |
Circular or oval orange or reddish brown spots usually appear on older leaves. Under damp conditions, fuzzy gray fungal spores form on spots. Brown spotting of blooms occurs. Botrytis elliptica infects healthy tissue whereas B. cinerea invades only dead or dying tissue. | In plant debris. Spores are airborne. Favored by cool, wet conditions and condensed moisture on plant parts. | Keep humidity below 85% by heating and ventilation. Do not use overhead irrigation. Mist blooms and foliage with iprodione, mancozeb, or fenhexamid. |
| Bulb rots (Rhizopus spp., Penicillium spp.) |
Bulb rot may be soft and mushy (Rhizopus spp.) or dry and rotted (Penicillium spp.) | In plant debris. Spores are airborne. Favored by warm storage temperatures. | Do not injure bulbs. Store bulbs under cool and dry conditions. Thiabendazole bulb dips usually prevents Penicillium decay. |
| Fusarium bulb rot (Fusarium oxysporum f. sp. lilii) |
Lower leaves become yellow or purple and die. Plants are stunted and of poor quality. Brown basal rot of bulb occurs, causing the scales to fall off. | In diseased bulbs and soil. Favored by warm temperatures. | Do not plant bulbs that show any signs of infection. Dip bulbs in thiabendazole. Plant deep in pot to force stem roots. |
| Leaf scorch (nonparasitic) |
Semicircular brown areas develop along leaf margins. Leaf tips turn brown. | Most severe in high-acid and low-fertility soils. | Adjust soil pH to 6.5 or 7.0. Maintain adequate levels of nitrogen and calcium. |
| Root rots * (Pythium spp., Rhizoctonia solani) |
Roots turn brown and rot. Plants are stunted with yellowing of lower leaves and leaf scorch. Buds are blasted, resulting in a reduced bud count. | In soil and on bulbs. Favored by overwatering and poor drainage. | Drench plants with mefenoxam in combination with thiophanate-methyl. Mefenoxam at high rates may cause yellowing of leaf margins of Easter lilies. |
| Shoot rot (Phytophthora cactorum) |
Growing points of emerging plants are rotted. Stems of older plants are rotted, causing the plants to wilt and collapse. Roots are also frequently rotted. | Soilborne. Spores are spread in water. Favored by poorly drained soil and overwatering. | Steam or chemically treat soil. Oomycete (water mold) specific fungicide drenches also help control the fungus. (See root rot control, above.) |
| Virus or viruslike disease | Symptoms | Host range and natural spread | Comments on control |
| Fleck (Cucumber mosaic virus and Lily symptomless virus) |
Small, brown, elongated spots appear parallel to leaf veins mostly on older leaves. Flowers are smaller and fewer than on healthy plant | Many hosts; transmitted by aphids. | Remove infected plants and control aphids. |
| Mosaic (Tulip breaking virus) |
Foliage shows a slight, dark and light green mottling. Plants are usually salable. | Spread by aphids. | Obtain virus-free bulbs, if possible. Control aphids. Destroy infected plants. Root rot is more severe on virus-infected plants. |
| Rosette (Lily rosette virus) |
Leaves curl downward and are flat. Internodes are shortened, giving plants a flat rosette or cylindrical appearance in contrast to pyramid shape of a healthy plant. Flowers fail to open correctly. | Symptoms tend to be masked at high temperatures (above 75°F). | |
| Easter Lilies are also susceptible to foliar nematodes (Aphelenchoides olesistis)** that cause bunchy top and black scale rot (Colletotrichum lilii). | |||
| * For additional information, see section on Key Diseases. |
| ** For additional information, see section on Nematodes. |