Fasciation causes development of short, thick stems with misshapen leaves near the crown. Infected plants should be removed and destroyed. No chemical controls are listed.
Bacterial leaf spot causes dark brown to black spots on the leaves. The spots are slightly sunken and have concentric zonations. Spray with basic copper sulfate.
Verticillium wilt causes the leaves to yellow and turn brown, starting with the lowest leaves. Infected plants are stunted and fail to bloom. Avoid infested soil and destroy infected plants. No chemical controls are listed.
Rust symptoms are blister-like swellings which break open and discharge masses of brown powdery spores. Severely infested plants are weakened and fail to bloom properly. Spray with sulfur to control rust.
A number of leaf spot diseases can attack chrysanthemum. The leaves are spotted and in severe cases, may die and drop. Pick off and destroy infected leaves. A general leaf spot spray is basic copper sulfate.
Blight or gray mold attacks the flowers, flower buds and leaf tips. Symptoms on flowers are small water soaked spots which enlarge rapidly, followed by development of a gray mold. Infected plants and plant parts are removed and destroyed. Applications of benomyl or chlorothalonil will control this disease.
Powdery mildew causes a powdery white coating on the leaves. This disease is controlled with benomyl or sulfur.