Symptoms: Galls ( knots ) form on roots.
Treatment: Not much unfortunately start a new plant from leaf cuttings.
Symptoms: Older leaves drop and as crown rot progresses younger leaves start to drop as well. Stems are water soaked and weak. Roots become brown and die.
Cause: over watering
Treatment: Sometimes fungicides can help. They can be found at your local nursery. Also get the plant out of the wet soil and into fresh, sterile soil. It is organisms that actually do the damage.
Symptoms: Small spots appear on leaves and stems. The spots will enlarge, often quickly covering the entire leaf. Flowers look faded. A close look might show gray fungus.
Treatment: none – remove infected plants before the blight can spread to your other plants.
Symptoms: White filaments grow on leaves, stems, flowers, they will look like powder. It might only effect flowers.
Treatment: Use a fungicide available at your local nursery.
Symptoms: Rust colored spots appear where stem touches pot or soil. The stem and leaf collapse.
Cause: Too much salt accumulation in soil. This means too much fertilizer.
Treatment: Repot in a fresh pot with fresh soil and go easy on the fertilizers.
Symptoms: Rings appear on leaf surface, they might be white, yellow, or brown. Leaves affected eventually die.
Cause: Cold water touching the leaves
Treatment: Use warm water to water African Violets.