Agriculture: Floriculture and Ornamental Nurseries Pest Management Guidelines

Sweet William

  • Dianthus barbatus
  • 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.
    Text Updated: 11/20