Big problem on gazania used for ground cover. Loose mycelium may form and black sclerotia on surface or in hollow pith. Environment - favored by cool, moist conditions. Our winters are very conducive. Cycle - virtually all survival is in sclerotia, but infected perennial plants may harbor mycelial infections.
Most infection is from primary inoculum.
Secondary cycles are very limited. Sclerotia are difficult to kill. Avoid excess moisture and space plants widely to allow ventilation. Fungicides are of little value. PCNB is effective but has limited registration.