African Violet Diseases When Leaf Edges Turn Black

Bacterial Blight

• African violets exposed to the Erwinia chrysanthemi bacteria may develop a serious soft rot disease. This bacteria can damage practically every part of an African violet, including roots, stems and leaves, according to the University of Florida. Leaves may become discolored and curl around the edges as a result of root deterioration. Leaves that are directly infected by the bacteria become completely discolored. Some cultivars of African violet may be more resistant to this bacterial illness than others, but the majority of violets in circulation can contract this illness. Bacterial soft rot eventually causes the entire plant to wilt and collapse from structural damage.

Phytophthora Rot

• African violets are prone to a rot disease caused by fungal species in the Phytophthora genus. Infections of these fungal pathogens leads to serious root and stem damage, which produce noticeable discoloration of foliage and other green growth. Damage to foliage often emerges as dark discoloration along the edges of the leaf near its base. The stem tissue connected to the leaf may also become darkened or distorted. Phytophthora can infect the stems and other tissue that support the plant's flowers, which can cause flowers to fall from the plant before blooming.

Pythium Rot

• Fungal species in the Pythium genus cause diseases on a large number of herbaceous and woody plant species, including African violets. Violets infected with this pathogen develop a crown and root rot disease that can produce serious or fatal symptoms. The fungus usually infiltrates its host's roots and systematically spreads throughout the entire plant through its circulatory system. The fungus can starve foliage and other remote growth by clogging the plant's circulatory pathways and deteriorating its roots. Pythium fungal spores can propel themselves in liquids, so they are more likely to spread and infect plants growing in saturated soil with poor water drainage.

Botrytis Blight

• A fungal blight disease caused by Botrytis cinerea is one of the most severe ailments of African violets in the United States. This condition is particularly common in controlled, indoor environments like greenhouses, according to "African Violet Magazine." External symptoms of an infection include patches of gray discoloration on buds and leaves. Damaged leaves may turn brown or black as the infected tissues decay. Infected plants should be removed from a garden or greenhouse immediately to prevent the disease from spreading.