Rose powdery mildew (Sphaerotheca pannosa var. rosae) – identify and control

Rose powdery mildew-identify-and-control

Rose powdery mildew, Sphaerotheca pannosa var. Rosae is widespread in all countries manifesting itself both in field crops and in those in protected areas.

Symptoms. The rose powdery mildew is manifested on leaves, young branches, flower buds, or even on fruits, during the whole growing season. Irregular spots in size and shape, white, with a powdery appearance appear on both sides of the attacked leaves when the asexual part of the fungus is formed, respectively of the conidiophores with conidia. As the attack progresses, the spots enlarge and partially or completely cover the leaf. They turn yellow, turn brown, wither and drop. The attacked young branches are covered with a thick, whitish powdery dust at first. In a more advanced stage of the disease, it acquires a yellow color. In autumn, in the mycelium on the branches, the fungus differentiates the cleistothecia that have the appearance of small, brown spots.

The attacked branches do not lignify properly and suffer frost injury during the winter. Frequently, the affected flower buds are covered with powdery growth, remain smaller, and no longer form flowers. Sometimes the attacked flowers are deformed, small.

The pathogen is Sphaerotheca pannosa var. rosae. The fungus lasts from one year to the next in the form of cleistothecia and resistance mycelium in buds or on branches, especially at the base of thorns.

Prevention and control. To prevent the disease, the strongly attacked shoots will be pruned and burned. In protected areas, ventilation will be done frequently to reduce atmospheric humidity. Specific fungicide treatments are required during the growing season.

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Rose powdery mildew (Sphaerotheca pannosa var. rosae) – identify and control
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