Gerbera Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| ALTERNARIA LEAF SPOT | Brown specks form on florets and the leaves. Centers become white on the leaf spots. | Alternaria | Maintain low relative humidity and do not wet leaves when watering. Apply azoxystrobin or fludioxonil. |
| BACTERIAL LEAF SPOT | Small to large spots are circular at first, then become irregular and dark brown to black. May have a concentric ring pattern. | Pseudomonas cichorii | Maintain low relative humidity. Avoid overhead watering. |
| BOTRYTIS BLIGHT | Petioles have long brown spots. Leaves yellow and die. Petals have tan spots. Stems at soil level are killed. Infected tissues become covered with gray fungal growth. | Botrytis cinerea | Space plants to insure good air circulation. Maintain low humidity. Avoid watering late in the day. Remove crop debris. Apply azoxystrobin or fludioxonil to protect healthy plants. |
| FUSARIUM STEM ROT | Petiole of leaves blacken at the base as the plant collapses. | Fusarium solani | Plant in pasteurized potting media. Discard infected plants. |
| PHYTOPHTHORA CROWN ROT | Plants wilt suddenly. Leaves brown. Roots are rotted and a crown rot develops. | Phytophthora cryptogea | Plant in pasteurized potting media. Avoid overhead watering. Apply etridiazole or etridiazole + thiophanate methyl to protect healthy plants. |
| POWDERY MILDEW | White fungal growth develops on the surface of leaves. | Golovinomyces cichoracearum (formerly Erysiphe) | Apply triadimefon, kresoxim-methyl, azoxystrobin, or piperalin to protect plants |
| PYTHIUM ROOT ROT | Plants wilt and die as roots rot. | Pythium | Plant in pasteurized potting media. Apply etridiazole or etridiazole + thiophanate methyl to protect healthy plants. |
| RHIZOCTONIA CROWN ROT | Stems at the soil level have a brown lesion. Plants wilt and die. | Rhizoctonia solani | Plant in pasteurized media. Apply azoxystrobin, PCNB, thiophanate methyl or etridiazole + thiophanate methyl to protect healthy plants. |
| THIELAVIOPSIS ROOT ROT | Plants yellow, wilt, and die. Roots are dark brown to black. | Thielaviopsis basicola | Plant in pasteurized media. Apply thiophanate methyl or etridiazole + thiophanate methyl to protect healthy plants. |
| VIRUSES | Leaves may be mottled, have yellow spotting, dead flecks, line or ring spot patterns. Plants may be distorted or have flower color breaking. | Tobacco rattle, gerbera mosaic, impatiens necrotic spot, and cucumber mosaic viruses. | Maintain good insect and mite control. Plant in pasteurized media. Destroy infected plants |
Fusarium crown rot.
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 | triadimefon | 12 | Strike (3125-436), Bayleton (432-1360) |
| 5 | Piperidine | piperalin | 24 | Pipron (67690-1) | |
| 11 | 3 | Strobilurin | azoxystrobin | 4 | Heritage (10182-408) |
| kresoxim-methyl | 12 | Cygnus (7969-124) | |||
| pyraclostrobin | 12 | Insignia (7969-184) | |||
| 14 | 1 | Aromatic | |||
| hydrocarbon | PCNB | 12 | Revere (400-407-10404), Blocker (5481-211), Terraclor (400-399), Defend (5481-444-1001) | ||
| Thiadiazole | etridiazole | 12 | Truban (58185-7), Terrazole (400-416) | ||
| 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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