Q Can you tell me more about rose powdery mildew?
A Rose powdery mildew (Sphaerotheca pannosa) is also very common and widespread. The symptoms appear mainly on the younger shoots. The leaves become distorted and puckered, and buds fail to open. A greyish, powdery deposit appears on the leaves, stems or buds, and can turn the whole shoot a dirty white.
Caption: Rose powdery mildew tends to occur in dry weather
Q How does rose powdery mildew spread?
A The fungus produces spores which are spread by the wind. It overwinters on stems or in buds, not on the leaves.
Q How do I control rose powdery mildew?
A Powdery mildew tends to be worse when plants are short of water, and where air circulation is poor – so plants growing against walls are particularly vulnerable. Water well in dry spells but avoid wetting the leaves. Mulch in spring or autumn when the soil is moist. It is better to grow susceptible climbers on pergolas or arches, rather than walls or fences, to give better air circulation.
Mildew can weaken roses, and ruin their appearance, but is unlikely to kill them. You could spray with Bayer Garden Systhane; Westland Plant Rescue Control; Scotts Fungus Clear Ultra; Vitax Organic 2 in 1; Roseclear Ultra.