Coreopsis Diseases
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| Aster yellows | Flowers develop green, elongate, or stunted petals and an excessive number of flower heads. The affected plants are usually stunted and yellowed. | Phytoplasma | Maintain good leafhopper control and eliminate nearby weeds that harbor aster yellows. |
| Bacterial leaf spot | Irregular brown blotches and spots develop on leaves. | Pseudomonas cichorii | Water in a manner that keeps leaf surfaces dry and water when the leaves will dry quickly. Remove infected plants. Copper sulfate may protect leaves not yet infected. |
| Botrytis blight | Lower leaves die and become covered with white to gray, fluffy fungal growth that soon becomes a mass of gray spores. | Botrytis cinerea | Water in a manner that keeps leaf surfaces and flowers dry and water when the plants will dry quickly. Apply copper sulfate, fludioxonil, or trifloxystrobin. See NOTE below. |
| Crown rot | Plants wilt, brown, and die. White fungal growth webs at the base of the dying plant and become peppered with small, tan, round structures. | Sclerotium rolfsii | Remove infected plants. Mulch in a manner that does not hold moisture close to the stems. |
| Downy mildew | Black spots form on the upper leaf surface and white felt-like growth covers the underside of the leaf. | Plasmopara halstedii | Apply trifloxystrobin or copper sulfate. See NOTE below. |
| Fungal leaf spots | Purple to tan spots develop on leaves. | Cercospora, Septoria, Phyllosticta | Water in a manner that keeps leaf surfaces dry and water when the leaves will dry quickly. Apply trifloxystrobin or fludioxonil. See NOTE below. |
| Powdery mildew | White fuzzy growth develops on the upper side of the leaves. | Sphaerotheca macularis | Apply copper sulfatewhen mildew is observed. See NOTE below. |
| Root rot | Plants yellow, wilt, collapse, and die. | Phymatotrichopsis or Rhizoctonia | Apply trifloxystrobin or fludioxonil, See NOTE below. |
| Rust | Orange-yellow masses of spores form on the underside of leaves. | Coleosporium inconspicuum | See NOTE below. |
| Scab | Leaves have a coating of gray to brown spores. | Cladosporium coreopsidis | Water in a manner that keeps leaf surfaces dry and water when the leaves will dry quickly. See NOTE below. |
| Stem rot | Stems turn brown or tan and die as large portions of the plant collapse. | Alternaria sp., Rhizoctonia solani and Sclerotinia sclerotiorum | Remove infected plants. Cut plants back to the soil line in the fall. Mulch in a manner that does not hold moisture close to the stems. Apply trifloxystrobin or fludioxonil. See NOTE below. |
| Wilt | Plants wilt, turn brown and die. | Verticillium albo-atrum | Remove infected plants. This fungus survives in the soil for very long periods of time, even in the absence of susceptible plants. Do not plant susceptible varieties. |
Downy mildew. Fungal leaf spot.
NOTE: The fungicides listed in the table below list Coreposis specifically in their labels. There are other fungicides with very general labels for ‘ornamental use.’ These can be applied but the user assumes all liability for possible plant damage. If the label states that the fungicide is effective for a particular plant disease, apply the chemical to a few plants and wait 24-48 hrs to see if damage occurs. If none occurs, it may be safe to use that chemical more extensively on that variety and test it on other varieties prior to extensive use.
Active Ingredients and Trade Names of the Chemicals
Fungicides and Fungicide Resistance Management - Certain fungicides, usually systemic chemicals, are said to be ‘at risk’ to the development of resistance if they are used repeatedly. See the Risk Level in the table; 1 = low risk; 2 = moderate risk; 3 = high risk. Fungicide Resistance Action Committees (FRAC) have developed a numbering system in which chemicals with the same FRAC Group number have the same mode of action. That is, chemicals with the same FRAC number kill the fungus in the same way (See http://www.frac.info/frac/index.htm). If a fungus has resistance to a chemical with a particular FRAC number, it is most likely resistant to all the other chemicals with that same number. 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).
| FRAC Group | Risk | Class | Active Ingredient | REI Restricted Entry Interval | Trade Names (EPA Reg. no.) |
|---|---|---|---|---|---|
| 11 | 3 | strobilurin | trifloxystrobin | 12 | Compass (432-1371) |
| 12 | 2 | Phenylpyrol | fludioxonil | 12 | Medallion (100-769) |
| M | 1 | copper, complex | Copper sulfate | 24 | Phyton 27 (49538-3) |
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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