African Violet Diseases
|Bacterial Blight||Dark reddish brown to black rotting areas form on roots and crown. Infected petioles have a greasy appearance.||Erwinia chrysanthemi||Pot and propagate in pasteurized media. Do not take cuttings from infected plants. Avoid high temperature, high humidity conditions. Keep plants separate from new plants, especially foliage plants of unknown health.|
|Botrytis Blight||Small water-soaked lesions form on damaged petioles and spread to leaf blades. Infected flowers fade prematurely.||Botrytis cinerea||Space plants and provide ventilation to avoid excessively high humidity. Remove fading flowers and yellowing leaves. Apply a fungicide to protect healthy tissue.|
|Foliar Nematode||Small tan, sunken areas form on lower surfaces of leaves. Spots become dry and dull black as they enlarge. Plants are stunted.||Aphelenchoides ritzema-bosi||Destroy infected plants. Water plants in a manner that keeps leaf surfaces dry and does not splash from plant to plant.|
|Phytophthora Crown Rot||Crowns and roots have a dark, water-soaked appearance. This spreads to petioles and leaf blades. Leaves remain firmly attached as the plant collapses.||Phytophthora nicotianae, P. cryptogea||Do not propagate from infected plants. Pot in pasteurized media Destroy infected plants. Apply a fungicide to protect healthy tissue.|
|Powdery Mildew||White, mealy fungal growth on the leaves and flowers causes them to dry and die.||Oidium||Apply a fungicide to protect healthy tissue.|
|Pythium Root Rot||Roots are dark brown. Plants are wilted and yellowed||Phythium||Do not propagate from infected plants. Pot in pasteurized media Keep hose end off the ground. Apply a fungicide to protect healthy tissue.|
|Rhizoctonia Crown Rot||Plants wilt, collapse, blacken, and die. A reddening of infected tissue may occur at soil line. Leaves readily detach from collapsing plants.||Rhizoctonia||Destroy infected plants. Pot in pasteurized media. Apply a fungicide to protect healthy tissue.|
|Ring Spot||Bright yellow or bleached ring patterns form on dark green leaves.||Irrigation water mluch colder or warmer than the leaf surface causes cells to collapse.||Keep irrigation water off the foliage. Use water that is at room temperature.|
Phytophthora crown rot
Cold water spotting
Prepared by Gary W. Moorman, Professor of Plant Pathology
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Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
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