Periwinkles (Catharanthus roseus), commonly known for their vibrant colors and adaptability as bedding plants, often fall victim to a devastating fungal disease called aerial phytophthora, also known as periwinkle blight. This disease, caused by the fungus Phytophthora parasitica, can spread rapidly under favorable conditions, leading to the decline and death of periwinkle plants.
Key Facts
- Aerial Phytophthora: Periwinkles can be infected with a fungal disease called aerial phytophthora, also known as periwinkle blight. This disease is caused by the fungus Phytophthora parasitica and can spread rapidly under conditions of frequent overhead irrigation or rainfall.
- Symptoms of Aerial Phytophthora: The initial symptoms of aerial phytophthora include water-soaked, gray-green, “greasy” areas on the shoots and leaves. This is followed by a sudden wilting of shoots, and dark brown lesions develop on the stems. The disease can progress rapidly, and plants may die within one to two weeks after symptoms appear.
- Prevention and Management: To prevent periwinkles from dying due to aerial phytophthora, it is recommended to follow these guidelines:
- Plant periwinkles after Mother’s Day, as they are summer bedding plants and prefer hot and dry conditions.
- Choose healthy transplants with no dead shoots or brown lesions on the stems.
- Avoid overhead irrigation, as aerial phytophthora is spread by water. Periwinkles rarely need supplemental irrigation after being initially watered in.
- Plant periwinkles in full sun and well-drained soils.
- Avoid over-fertilization, as new succulent shoots are more prone to the disease.
- Remove dead shoots or dying plants immediately to minimize the disease in the future.
- Avoid planting periwinkles in beds with a history of aerial phytophthora.
- Consider planting periwinkles from the Cora series, as they have some genetic resistance to the disease.
- Chlorothalonil (Daconil) fungicide can be used to protect healthy plants from the disease, but it will not cure infected plants.
Symptoms of Aerial Phytophthora
The initial signs of aerial phytophthora manifest as water-soaked, gray-green, and “greasy” areas on the shoots and leaves of periwinkles. This is swiftly followed by a sudden wilting of shoots, accompanied by the development of dark brown lesions on the stems. The disease progresses rapidly, and infected plants may succumb within one to two weeks after the onset of symptoms.
Prevention and Management Strategies
To effectively prevent and manage aerial phytophthora in periwinkles, it is crucial to implement the following measures:
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Planting Considerations:
- Avoid planting periwinkles before Mother’s Day, as they are summer bedding plants that thrive in hot and dry conditions.
- Select healthy transplants devoid of dead shoots or brown lesions on the stems.
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Irrigation Practices:
- Refrain from overhead irrigation, as aerial phytophthora is primarily spread through water.
- Periwinkles typically require minimal supplemental irrigation after the initial watering.
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Site Selection and Soil Conditions:
- Plant periwinkles in areas with full sun exposure and well-drained soils.
- Avoid over-fertilization, as new succulent shoots are more susceptible to the disease.
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Sanitation and Removal:
- Promptly remove dead shoots or dying plants to minimize the spread of the disease.
- Avoid planting periwinkles in beds with a history of aerial phytophthora.
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Resistant Varieties:
- Consider planting periwinkles from the Cora series, as they exhibit some genetic resistance to the disease.
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Chemical Control:
- Chlorothalonil (Daconil) fungicide can be applied to protect healthy plants from the disease, but it is ineffective in treating infected plants.
By adhering to these guidelines, gardeners can effectively prevent and manage aerial phytophthora in periwinkles, ensuring the health and longevity of these vibrant bedding plants.
FAQs
What causes periwinkles to die?
– Periwinkles can die due to a fungal disease called aerial phytophthora, also known as periwinkle blight. This disease is caused by the fungus Phytophthora parasitica and can spread rapidly under favorable conditions.
What are the symptoms of aerial phytophthora in periwinkles?
– Initial symptoms include water-soaked, gray-green, and “greasy” areas on the shoots and leaves, followed by sudden wilting of shoots and the development of dark brown lesions on the stems.
How can I prevent aerial phytophthora in my periwinkles?
– Preventive measures include planting periwinkles after Mother’s Day, choosing healthy transplants, avoiding overhead irrigation, planting in full sun and well-drained soils, avoiding over-fertilization, removing dead shoots or dying plants, and avoiding planting in beds with a history of the disease.
Are there any resistant periwinkle varieties?
– Yes, periwinkles from the Cora series exhibit some genetic resistance to aerial phytophthora.
How can I treat aerial phytophthora in my periwinkles?
– Chlorothalonil (Daconil) fungicide can be applied to protect healthy plants from the disease, but it is ineffective in treating infected plants.
How can I prevent the spread of aerial phytophthora?
– To prevent the spread of the disease, promptly remove and discard infected plants, avoid overhead irrigation, and maintain good garden sanitation practices.
What are some alternative plants that are resistant to aerial phytophthora?
– Some alternative plants that are resistant to aerial phytophthora include impatiens, begonias, marigolds, and zinnias.
Can I compost periwinkle plants infected with aerial phytophthora?
– No, it is not recommended to compost periwinkle plants infected with aerial phytophthora, as this can spread the disease to other plants.