One to 20 (commonly two to five) small, black sclerotia (a fungal resting stage) form on an infected flower 6–8 weeks later.

Caused by the Ovulinia azaleae fungus, the disease develops during periods of moist weather at flowering time.

The fungus overwinters as sclerotia on diseased petals adhering to plants, on the soil surface, or in leaf mulch under the bushes.

Spraying the infested soil with fungicides and removal of the leaf litter beneath infected plants have not been reliable methods of disease control.

[9] In general, sprays of triadimefon or benomyl applied at weekly intervals throughout the flowering period have controlled the blight and inhibited sclerotium formation.