Petunia Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| BOTRYTIS BLIGHT | Flowers have small translucent, or dead spots. | Botrytis cinerea | Maintain low relative humidity. Apply chlorothalonil, mancozeb, or fludioxonil to protect plants. |
| PHYTOPHTHORA CROWN ROT | Branches wilt and the plant rapidly dies as the crown. Young plants are quickly killed. Outdoors if the weather is dry, the stem at the soil line may have a dry rot. | Phytophthora nicotianae | Use pasteurized potting mix or soilless mix known to be free of pathogens. Discards flats containing infected plants. Apply mefenoxam, dimethomorph, chlorothalonil, etridazole, etridiazole + thiophanate methyl, or propamocarb to protect remaining plants. |
| STUNT | Young plants are stunted and thick. | Lack of boron | Maintain a soil pH below 7. Have a water test done to be certain calcium and sodium are not too high. |
| VIRUS | Small etches on the leaf are surrounded by a dark halo. | Impatiens necrotic spot virus (INSV) | Destroy infected plants. Take steps to control western flower thrips. Examine other plants in the greenhouse for INSV symptoms and destroy them. |
Petal spotting caused by Botrytis
Active Ingredients and Trade Names of the Chemicals
| FRAC Group No. | Risk Level | Class | Active ingredient | Restricted Entry Interval | Trade names (EPA Reg. no.) |
|---|---|---|---|---|---|
| 4 | 3 | Acylanine | mefenoxam | 0 | Subdue MAXX (100-796) |
| 12 | 2 | Phenylpyrol | fludioxonil | 12 | Medallion (100-769) |
| 14 | 1 | Thiadiazole | etridiazole | 12 | Truban (58185-7), Terrazole (400-416) |
| 28 | 1 | Carbamate | propamocarb | 12 | Banol (432-942) |
| 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) | ||||
| Dithiocarbamate | mancozeb | 24 | Dithane (707-180), FORE (707-87), Pentathlon (1818-251) | ||
| manganese + zinc | 24 | Protect T/O (1001-65) | |||
| ferbam | 24 | Ferbam (45728-7) | |||
| ziram | 48 | Ziram (4581-140) | |||
| 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).
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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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