Downy fungal blight

A picture of a rosehip plant infected with downy fungal blight

English name: Powder Mildew

The scientific name: Podosphaera pannosa, Sphaerotheca pannosa

The type of disease: Fungal disease

the family: Erysiphaceae


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.

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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.


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


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