Rose Disease and Powdery Mildew
Powdery mildew is a rose disease that appears as a white powdery growth on rose leaves, stems, buds or flowers. This disease often occurs when the days are warm and dry and the nights are cool and damp. Does this Spark an idea?
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Cause
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The fungus Sphaerotheca pannosa is the cause of powdery mildew on roses.
Effects
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Fungus spores usually mature and settle on the flowers during the day when the relative humidity is low. With lower temperature and increased humidity at night, the spores germinate and the fungus infects the plants.
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Prevention
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Dampness and lack of airflow promote the growth of mildew, so it's important to plant roses where they receive a good amount of sun, usually at least six hours a day, and good airflow. You can also regularly spray the roses with a preventative fungicide.
Treatments
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Fungicides are usually used to treat powdery mildew. A natural treatment is to spray your roses once a week with 2 tbsp. white or cider vinegar mixed in 1 gallon of water.
Considerations
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Moderate temperatures and humid (not wet) conditions promote the growth of powdery mildew. Some varieties of roses resist powdery mildew better than others, so ask your county extension office or a local plant nursery which types of roses thrive best in your location.
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References
Resources
- Photo Credit gelbe rose - yellow rose image by Yvonne Baumann from Fotolia.com
