Informational table showing disease name, symptoms, pathogen/cause, and management of Aster diseases. Disease Symptoms Pathogen/Cause Management Aster Yellows Leaves yellow. Abnormal branching occurs. Yellowed, leaf-like tissue forms instead of flower parts. Phytoplasma Destroy infected plants. Maintain good leafhopper control. Destroy any similarly affected weeds in the vicinity. Botrytis Blight Brown specks form on petals. The entire flower browns and dies. Botrytis cinerea Avoid sprinkler irrigation.  Apply a fungicide to protect healthy tissue. Fusarium Wilt Young seedlings are killed. Older plants are stunted and have yellowing and wilting up one side of the plant. Water conducting tissue in the stems browns. Fusarium oxysporum Use potting soil that has been treated to eliminate pathogens. Or, use soilless potting mix. Leaf Spots Spots form on leaves. Leaves Yellow, wilt, and die. Usually lower leaves are affected first and symptoms progress upward. Alternaria, Ascochyta, Cercospora, Septoria Avoid sprinkler irrigation.  Apply a fungicide to protect healthy tissue. Powdery Mildew White felty growth develops on the surface of leaves. Leaves wither and die. Golovinomyces cichoracearum (formerly Erysiphe) Apply a fungicide to protect healthy tissue. Rust Reddish-orange masses of spores form on the underside of leaves. Severely affected leaves yellow and die. On the alternate host, pines, blisters of spores form on needles in the spring. Coleosporium solidaginis No control is recommended.