Informational table showing disease name, symptoms, pathogen/cause, and management of Delphinium diseases. Disease Symptoms Pathogen/Cause Management Aster Yellows Leaf-like tissue forms where flower parts should be located. Flower-like parts remain green or light green. Often flowers on only one side of the spoke show sympotms. Sepals may be very large or dwarfed. Phytoplasma Destroy infected plants. Control leafhoppers. Bacterial Bud Rot, Crown Rot, and Stem Rot Yellowed leaves and stunting occurs. Blackened stem bases around cracks and wounds mark the point of entry. Smelly ooze forms under wet conditions. Infected stems topple. Erwinia carotovora and Erwinia chrysanthemi Promptly destroy infected plants. Avoid overhead irrigation. Bacterial Stem Rot Black, irregularly shaped spots form on leaves. Seedlings are killed. Pseudomonas syringe Destroy infected plants. Diaporthe Blight As the plants flower, lower leaves brown and die. Brown spots form on the stems at the soil line and expand upward several inches. Small, black, pimple-like fungal fruiting structures develop on infected tissue. Diaporthe Destroy infected plants. Use seed known to be free of the fungus. Fusarium Wilt and Canker Small brown spots form on stems and enlarge. Brown, sunken lesion may occur on petioles. Stem cankers may be dark brown and 12 inches long. As the canker tissue dies, masses of pink spores form in clumps. Wilting plants have vascular tissue that is browned. Fusarium oxysporum Destroy infected plants. Powdery Mildew Dry, white, mealy, fungal growth occurs on the upper surface of leaves. Leaves turn yellow, die from the base of the stem upward. Erysiphe polygoni Apply a fungicide when the fungus is first observed. Destroy plant debris at the end of the season. Storage Rot Tubers decay into a soft smelly mass. Various fungi and bacteria. Avoid wounding the tubers when digging them for storage. Let the tuber surfaces dry after digging and removing soil and before storing. Store tubers in a cool, dry location. Virus Conspicuous rings and line patterns may be present and plants are stunted. Cucumber and tobacco mosaic viruses. Destroy infected plants.

Prepared by Gary W. Moorman, Professor of Plant Pathology