In jenny2write wrote:
I have a bourbon shrub rose "Boule de Neige" which is in a large pot.
Last year it flowered beautifully but this year buds start developing
normally then instead of opening they shrivel up and form a ball. The
petals themselves seem to get stunted and shrink and shrivel before
they get to a size where they should open. They don't even try to
open. It happened with every single bud. Has anyone got any
suggestions as to how to manage this please?

From what you've told me, it could be a fungal condition and mildew
would be the prize suspect. Jenny, is there a white powdery coating on
the flower buds and surrounding young leaves?