Fall asters are being produced and sold along side of mums in many Delaware greenhouses and nurseries. The following are some diseases common on fall asters that you may have to manage.
- Leaf spots (Alternaria sp., Ascochyta compositarum, Cercospora asterata, Cercosporella cana, Ramularia asteris, Septoria asteris, and S. astericola). Control watering to avoid prolonged
- Downy mildew (Basidiophora entospora). Control as soon as problem arises with fungicides specific for downy mildew.
- Powdery mildew (Erysiphe cichoraceurum). Mildew that is comonly found on the lower
half of asters. Start control as soon as mildew is apparent using fungicides specific for powdery mildew
- Rusts (Coleosporium soldaginis, Puccinia asteris, P. extensicola, P. grindeliae, P. stipae, Uromyces compactus, and U. junci). Avoid alternate hosts; pines, grasses, and sedges
Gordon Johnson, Extension Horticulture Agent, UD, Kent County