Impatiens Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| ALTERNARIA LEAF SPOT | Brown spots and rings form on infected leaves. | Alternaria | Reduce humidity and maintain good air circulation. Space plants for good air circulation. Apply iprodione to protect plants. Or, apply chlorothalonil if plants are not flowering, chlorothalonil |
| BOTRYTIS BLIGHT | Flowers are spotted and stems rot. | Botrytis cinerea | Reduce humidity and maintain good air circulation. Do not space plants too closely. Remove fading flowers and yellowing leaves. Apply iprodione to protect plants. If plants are not flowering, chlorothalonil can be applied. |
| BACTERIAL FASCIATION | Plants stunted and have many short shoots at the crown. | Corynebacterium fascians | Discard infected plants. Do not propagate from infected plants. Propagate and plant in pasteurized potting media. |
| DAMPING-OFF | Stems at the soil line die and plants collapse. | Pythium or Rhizoctonia | Plant in pasteurized potting media. Keep hose ends off the ground. |
| POWDERY MILDEW (New Guinea impatiens) | White, mealy fungal growth develops on the top of leaves. Sometimes, heavy gray growth develops. | Oidium | Apply triflumizole to protect plants. If plants are not flowering, chlorothalonil can be applied. |
| PYTHIUM ROOT ROT | Lower leave wilt, leaves fall, and the plant dies. | Pythium spp. | Pot in pasteurized, pathogen-free media. Keep hose ends off the ground. Apply potassium salts of phosphorus acid, dimethomorph, mefenoxam or fosetyl-Al to protect healthy plants. |
| THIELAVIOPSIS ROOT ROT | Roots become dark brown and rot. Lower stems have sunken lesions when infected. | Thielaviopsis basicola | Pot in pasteurized, pathogen-free media. Keep hose ends off the ground. Apply thiophanate methyl or etridiazole + thiophanate methyl to protect plants. |
| VERTICILLIUM WILT | Lower leaves yellow and fall. Infected plants may recover. | Verticillium dahliae | Pot in pasteurized, pathogen-free media. Do not take cuttings infected plants. |
| VIRUS | Ring spots on leaves. Death of growing tips. Severe stunting. | Impatiens necrotic spot virus | Discard infected plants. Control thrips that carry the virus. Do not propagate from infected plants. |
Alternaria leaf spot.
Powdery mildew
Impatiens necrotic spot virus symptoms.
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) |
| 2 | 3 | Dicarboximide | iprodione | 12 | Chipco 26GT (100-1138), Chipco 26019 (264-481), Iprodione (51036-361), Sextant (51036-361-59807) |
| 4 | 3 | Acylanine | mefenoxam | 0 | Subdue MAXX (100-796) |
| 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) | ||||
| U | 1 | Phosphonate | fosetyl-Al | 12 | Aliette (432-890) |
| Phosphite | phosphorus acid salts | 4 | Alude (71962-1-1001) | ||
| potassium phosphate | 4 | Vital (42519-24) | |||
| Combined products | 1 | ||||
| 1 + M | thiophanate methyl + etridiazole | Banrot (58185-10) |
Fungicides and Fungicide Resistance Management - Certain fungicides, usually systemic fungicides, are said to be 'at risk' to the development of resistance if they are used repeatedly. See the Risk Level in the above table (1 = low risk; 3 = high risk). The Fungicide Resistance Action Committee has developed a numbering system in which chemicals with the same FRAC Group number have the same mode of action (See http://www.frac.info/frac/index.htm ). It is recommended that chemicals at high risk be used sparingly and in rotation or mixed with chemicals with different modes of actions (different FRAC number).
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.
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