Michigan State University Extension
Ornamental Plants plus Version 2.0 - 00000363
01/01/98
Fasciation causes development of short, thick stems with misshapen leaves near the crown. Infected plants should be removed and destroyed.
Bacterial leaf spot causes dark brown to black spots on the leaves. The spots are slightly sunken and have concentric zonations.
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 available.
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.
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.
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.
Powdery mildew causes a powdery white coating on the leaves.