Whenever, the foliage of African violets are wetted, warm water must be used and sufficient time allowed for the leaves to dry out before dark. Foliage that stays moist is prone to fungal diseases. One common fungal foliar disease is powdery mildew. Infected leaves will have small circles of a gray or whitish powder on the topside of the leaves. Control for powdery mildew requires the removal of infected leaves and spacing plants out more for better air circulation between plants.
Powdery mildew tends to more of a problem on plants that are overcrowded.
Crown rot is another common fungal problem of African violets that are overwatered. Crown rot causes the main stem and lower leaves to appear water-soaked, shrivel and die. Crown rot usually leads to death of the plant. Allowing the top of the soil to dry out between watering will prevent crown rot. Prepared by Cindy Haynes , Department of Horticulture Iowa State University , Ames, Iowa.