Dieffenbachia Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Sympoms | Pathogen/Cause | Management |
|---|---|---|---|
| ANTHRACNOSE | Circular to oval brown leaf spots have a yellow halo. Spots may become two inches in diameter and contain tiny black fungal fruiting structures. | Colletrotrichum gloeosporioides | Avoid overhead watering. Apply mancozeb to protect healthy leaves. |
| BACTERIAL LEAF SPOT | Small gray or dark green leaf spots enlarge and become irregularly shaped, tan, dark brown, or black. | Erwinia carotovora or Erwinia chrysanthemi | Purchase plants free of the disease. Remove infected leaves and water in a manner that keeps the surface of the leaves dry. |
| WILT | Lower leaves yellow, wilt, and die. | Drought | Maintain even soil moisture. |
| MARGINAL LEAF BURN | Margins of leaves brown and die. | Over-fertilization | Do no overfertilize. If no slow-release fertilizer is present, leach the potting medium. |
| MYROTHECIUM LEAF SPOT | Large gray-brown, oval leaf spots form at leaf tips or margins. Fungal fruiting structures form in concentric rings within the spots on the underside of the leaf. | Myrothecium roridum | Do not apply excessive amounts of nitrogen fertilizer. Apply chlorothalonil, mancozeb, or thiophanate methyl + mancozeb. |
| NITROGEN DEFICIENCY | Plants are yellowed with smaller than normal leaves and short internodes. | Lack of fertilization. | Apply a balanced fertilizer solution. |
| VIRUS | "Leaves have a mosaic of light green where they should be dark green. Plants may be stunted, and leaves deformed. Some cultivars die within a month of infection." | Dasheen mosaic virus | "Discard infected plants. Maintain good aphid control. Disinfests tools used on the plants." |
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.) |
|---|---|---|---|---|---|
| M | 1 | Chloronitrile | chlorothalonil | 48 | Daconil (50534-9), Exotherm Termil (70-223) |
| 12 | Echo (60063-7), PathGuard Concorde (72167-24-1812),Pegasus (60063-7-499),(72167-24-1812) | ||||
| Dithiocarbamate | mancozeb | 24 | Dithane (707-180), FORE (707-87), Pentathlon (1818-251) | ||
| manganese + zinc | 24 | Protect T/O (1001-65) | |||
| Combined products | 1 | ||||
| 1 + M | thiophanate methyl + thiophanate methyl + | Zyban (58185-31) |
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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