| Disease | Symptoms | Pathogen/Cause | Management |
|---|
| Botrytis Blight | Petals turn brown and fall. Leaf spots form, especially where faded petals have fallen. Flower buds are killed before opening. | Botrytis cinerea | Space plants to insure good air circulation. Maintain low humidity. Avoid watering late in the day. Remove crop debris. Apply a fungicide to protect plants.
|
| Cercospora Leaf Spot | Tan spots with reddish-brown halos develop on leaves. | Cercospora | Water in a manner that keeps moisture off the leaves. Apply a fungicide to protect plants. |
| Powdery Mildew | Yellow areas form on leaves. These may become purplish. White, cottony fungal growth forms on the lower surface of the leaf. | Erysiphe polygoni | Apply a fungicide as soon as any mildew is observed.
|
| Virescence | Flowers are green and may be stunted. Leafy shoots grow from the flower parts. Plants decline and die. | Phytoplasma | Discard infected plants. Maintain good insect control. |
| Viruses | Leaves may be mottled, have yellow spotting, dead flecks, line or ringspot patterns. Plants may be distorted or have flower color breaking, or few flowers. | Hydrangea ringspot, tomato ringspot, impatiens necrotic spot | Plant virus-indexed cuttings. Maintain good insect and mite control. Destroy infected plants. |
