African Violet Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| 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, mancozeb, chlorothalonil or fenhexamid 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 etridiazole, etridiazole + thiophanate methyl, or mefenoxam to protect healthy plants. |
| POWDERY MILDEW | White, mealy fungal growth on the leaves and flowers causes them to dry and die. | Oidium | Apply myclobutanil, piperalin, or triadimefon to protect healthy plants. |
| 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. To protect, apply etridiazole, etridiazole + thiophanate methyl, or mefenoxam to protect healthy plants. |
| "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. To protect healthy plants, apply fludioxonil, etridiazole + thiophanate methyl. |
| 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
Active Ingredients and Trade Names of the Chemicals
| FRAC Group No. | Risk Level | Class | Active ingredient | REI Restricted Entry Interval | Trade names (EPA Reg. No.) |
|---|---|---|---|---|---|
| 1 | 3 | Benzimidazole | thiophanate methyl | 12 | 3336 (1001-69), OHP 6672 (51036-329-59807), Fungo Flo (51036-329-59807), Systec 1998 (48234-12) |
| 3 | 2 | Triazole | tridimefon | 12 | Strike (3125-436), (Bayleton (432-1360) |
| myclobutanil | 24 | Systhane (707-253) | |||
| 4 | 3 | Acylanine | mefenoxam | 0 | Subdue MAXX (100-796) |
| 5 | Piperidine | piperalin | 24 | Pipron((67690-1) | |
| 12 | 2 | Phenylpyrol | fludioxonil | 12 | Medallion (100-769) |
| 14 | 1 | Thiadiazole | etridiazole | 12 | Truban (58185-7), Terrazole (400-416) |
| 17 | 2 | Hydroxyanilide | fenhexamid | 4 | Decree (66330-35-67690) |
| 40 | Cinnamic acid derivative | dimethomorph | 12 | Stature (241-419-67690) | |
| M | 1 | Chloronitrile | chlorothalonil | 48 | Daconil (50534-9), Exotherm Termil (70-223) |
| 12 | Echo (60063-7), PathGuard (60063-7-499), | ||||
| Concorde (72167-24-1812), Pegasus (72167-24-1812) | |||||
DISCLAIMER
Notice: The user of this information assumes all risks for personal injury or property damage.
Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds.
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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