| Disease (causal agent) | Symptoms | Survival of pathogen and effect of environment | Comments on control |
|---|---|---|---|
| Fusarium wilt * (Fusarium oxysporum f. sp. dianthi) |
Yellowing of new growth. Plants stunted and leaves point downward instead of upward as in a healthy plant. Leaves gradually turn yellow and die. The vascular system of the lower stem and roots is brown. | Fungus survives in soil for many years as chlamydospores. Disease is favored by warm soils and high temperatures. | Fumigate soil with chloropicrin or a chloropicrin combination. Grow seedlings in heat-treated, solarized, or fumigated soil or growing medium. |
| Leaf spot (Cladosporium echinulatum) |
Yellowish brown, withered spots surrounded by a purplish margin on leaves. As the disease progresses, entire leaves and stems become necrotic. | Spores (conidia) are airborne. Fungus survives on sweet william debris. Favored by wet weather and overhead irrigation. | Avoid overhead irrigation. Protect foliage with a fungicide. |
| Sweet williams are also susceptible to rust * (Uromyces caryophyllinus and Puccinia arenariae), root rot * (Pythium ultimum), gray mold * (Botrytis cinerea), stem rot (Rhizoctonia solani), southern blight * (Sclerotium rolfsii), Septoria leafspot (Septoria dianthi), anther smut (Microbotryum violaceum, formerly Ustilago violacea), curly top (Beet curly top virus), and aster yellows * (aster yellows phytoplasma). | |||
| * For additional information, see section on Key Diseases. |