I have a lovely pot grown miniture rose that is covered in mildew. Does anyone know how I can treat it? I've tried mildew spray bought from the garden centre but it hasn't worked.
Thin out some of the stems, particularly the affected ones, so that the air can circulate around the plant more easily, and ensure that you water regularly, rather than over water once it's dry. Hopefully that will help.
There is a lot of this about this year, dry, heat and shade are the usual causes (in that order) Have you tried 'Roseclear' ? I've found it pretty good for most rose troubles.