English name: Powder Mildew
The scientific name: Podosphaera pannosa, Sphaerotheca pannosa
The type of disease: Fungal disease
the family: Erysiphaceae
Symptoms
Rose downy fungal blight appears as white or greyish-white downy growths on leaves, stems and buds.
Affected leaves may become distorted, curled, and eventually turn yellow or brown.
Severe infestations can result in stunted growth, reduced flower quality, and premature defoliation.
Fungal growth can also cover rose blossoms, making them appear misshapen or fail to open properly.
![Diseases of roses - the world of plants A close-up of a white and pink rose Description automatically generated](https://worldofplants.ai/wp-content/uploads/2024/05/a-close-up-of-a-white-and-pink-rose-description-a.jpeg)
![Diseases of roses - the world of plants A close-up of a plant stem Description automatically generated](https://worldofplants.ai/wp-content/uploads/2024/05/a-close-up-of-a-plant-stem-description-automatica.jpeg)
![Diseases of roses - the world of plants A close-up of a leaf Description automatically generated](https://worldofplants.ai/wp-content/uploads/2024/05/a-close-up-of-a-leaf-description-automatically-ge-3.jpeg)
![Diseases of roses - the world of plants A close-up of a rose bush Description automatically generated](https://worldofplants.ai/wp-content/uploads/2024/05/a-close-up-of-a-rose-bush-description-automatical.jpeg)
![Diseases of roses - the world of plants A close-up of a rose bud Description automatically generated](https://worldofplants.ai/wp-content/uploads/2024/05/a-close-up-of-a-rose-bud-description-automaticall.jpeg)
the reasons
Rose downy fungal blight is caused by the fungi Podosphaera pannosa and Sphaerotheca pannosa.
Propagation conditions
Downy blight thrives in warm, humid conditions with temperatures between 20°C and 27°C (68°F and 80°F) and high relative humidity.
The fungus can spread via wind and water splashes or by physical contact with infected plant material.
Disease course
Downy blight fungi can overwinter as dormant hyphae or closed cotyledons (fruiting structures) on rose stems, buds and plant debris.
In the spring, these structures release spores that can start new infections on young, sensitive tissue.
Next, the fungi produce additional spores (achenes) that can spread the disease throughout the growing season.
Losses
Severe downy blight infections can significantly reduce the aesthetic value and marketability of roses, as well as weaken plants and make them more susceptible to other diseases and environmental stresses.
Control strategy
An integrated approach including cultural practices, resistant varieties, and fungicide application is recommended to control downy blight.
Preventive measures
- Planting resistant or tolerant rose varieties.
- Ensure good air flow.
- Avoid crowds.
- Remove and destroy infected plant remains.
Organic/chemical control
For organic control, apply baking soda, neem oil, or sulfur-based fungicides.
Chemical fungicides containing active ingredients such as myclobutanil, trevvorin or tebuconazole can also be used according to label instructions, alternating between different classes of fungicides to prevent the development of resistance.
the reviewer
https://s3.amazonaws.com/opinsights.originalpaths.com/2018/04/Powdery-
Mildew-on-Rose-leaves.jpg
https://extension.umn.edu/plant-diseases/powdery-mildew-roses