Verbena Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| BOTRYTIS BLIGHT | Tan spots develop on leaves. Established plants rot at the crown. Infected tissue is covered with dusty gray fungal growth. | Botrytis cinerea | Maintain low humidity by spacing plants and venting to improve air circulation. Remove dead and dying flowers and leaves. To protect healthy plants, apply fenhexamid or fludioxonil. |
| POWDERY MILDEW | White fungal growth forms on the upper surface of leaves and may form on flower petals. | Golovinomyces cichoracearum (formerly Erysiphe) or Podosphaera xanthii (formerly Sphaerotheca fuliginea). NOTE: This powdery mildew can attack cucurbits and verbena. | Apply Ampelomyces , trifloxystrobin, or kresoxim methyl to protect plants. |
| PYTHIUM ROOT ROT | Roots are dark brown. Plants are wilted and yellowed. | Pythium sp. | Do not over-water plants. Pot in pasteurized media. Keep hose ends off the ground. To protect healthy plants, apply etridiazol + thiophanate methyl or mefenoxam. |
Bacterial leaf spot
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.) |
|---|---|---|---|---|---|
| 4 | 3 | Acylanine | mefenoxam | 0 | Subdue MAXX (100-796) |
| 11 | 3 | Strobilurin | kresoxim-methyl | 12 | Cygnus (7969-124) |
| trifloxystrobin | 12 | Compass (432-1371) | |||
| 12 | 2 | Phenylpyrol | fludioxonil | 12 | Medallion (100-769) |
| 17 | 2 | Hydroxyanilide | fenhexamid | 4 | Decree (66330-35-67690) |
| 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).
| Biological Control Agent (type of pathogen) | Trade Name (EPA Reg. No.) | Target Pathogens |
|---|---|---|
| Ampelomyces quisqualis (fungus) | AG10 (55638-16) | Powdery mildew |
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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