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Common African Violet Diseases: Identification and Management

Disease Reference Table

Disease	Symptoms	Pathogen/Cause	Management
Bacterial Blight	Dark reddish-brown to black rotting on roots and crown; infected petioles appear greasy.	Erwinia chrysanthemi	Pot and propagate in pasteurized media. Do not take cuttings from infected plants. Avoid high temperature/humidity. Keep separate from new/unknown plants.
Botrytis Blight	Small water-soaked lesions on damaged petioles spreading to leaf blades; flowers fade prematurely.	Botrytis cinerea	Space plants, ventilate to reduce humidity. Remove fading flowers and yellowing leaves. Apply fungicide to protect healthy tissue.
Foliar Nematode	Small tan, sunken spots on lower leaf surfaces; spots enlarge, become dry and dull black; plants stunted.	Aphelenchoides ritzema-bosi	Destroy infected plants. Water to keep foliage dry, avoid splash between plants.
Phytophthora Crown Rot	Crowns/roots dark and water-soaked; spreads to petioles and leaf blades; leaves remain attached as plant collapses.	Phytophthora nicotianae, P. cryptogea	Do not propagate from infected plants. Pot in pasteurized media. Destroy infected plants. Apply fungicide to protect healthy tissue.
Powdery Mildew	White, mealy fungal growth on leaves and flowers; causes drying and death.	Oidium	Apply fungicide to protect healthy tissue.
Pythium Root Rot	Roots dark brown; plants wilted and yellowed.	Pythium	Do not propagate from infected plants. Pot in pasteurized media. Keep hose ends off ground. Apply fungicide to protect healthy tissue.
Rhizoctonia Crown Rot	Plants wilt, collapse, blacken, die; reddening at soil line; leaves detach easily.	Rhizoctonia	Destroy infected plants. Pot in pasteurized media. Apply fungicide to protect healthy tissue.
Ring Spot	Bright yellow or bleached ring patterns on dark green leaves.	Irrigation water much colder/warmer than leaf surface causes cell collapse.	Keep irrigation water off foliage. Use room-temperature water.

Phytophthora crown rot; Cold water spotting

Plant Disease: African Violet Flower Color Change: Genetic Expression in Hybrid Plants; African Violet Pests in Self-Watering Pots: Emergency Rescue; Divided African Violet Still Traumatized After 6 Weeks: Recovery or Loss?; African Violet with Hairy New Leaves and Failed Blooms: Powdery Mildew or Mealybugs?; African Violet Care: Year-Round Blooms, Varieties, and Toxicity; African Violet Care: Complete Guide to Year-Round Blooms; Chrysanthemum Disease Guide: Comprehensive Identification and Management; Cyclamen Disease Guide: Comprehensive Management Strategies; Delphinium Disease Guide: Comprehensive Identification and Control; African Violet Care: Complete Guide to Growing Saintpaulia Indoors

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