Fusarium is a vascular wilt disease that develops within stems. Fusarium wilt results in symptoms similar to root rot but plants infected with Fusarium generally wilt in sectors, or one branch at a time and roots often appear healthy. Note the wilted branch in the front of the plant in the photo. Root rot usually results in the entire plant wilting. In later stages of Fusarium wilt, a white or pinkish fluffy mold may develop on the affected stems. Managing Fusarium centers on disease-free cuttings and pathogen-free root media.
See Fact Sheet: Diseases of Chrysanthemums