Pauline, it sounds like what is called Powdery or Down Mildew to me.
Pansies often suffer with this too.


Strangely, it often starts when plants have been have got too dry at the roots, and as Meg said, they need air round them as well.

Here's just a short exert for you:


Powdery Mildew: Powdery mildew doesn’t need soaking wet conditions to thrive, but often appears where plants are spaced too tightly, obstructing airflow.
Look for white, powdery spots of spores that spread or cover leaves and flowers completely. Powdery mildew can be treated with neem oil, but you should also correct the conditions allowing this disease to get a foothold."


Unfortunately I have never been able to cure my Pansies and usually end up pulling them up.

Yes the others are right Pauline, I knew it was to be really heavy rain and I put all my pots of Begonias, Petunias, and Dahlias into the greenhouse before it arrived. They are still in there with the door open so they don't get used to being inside.

Same here,Annie, Petunias need a lot of sunshine, most are now mouldy, I’ve cut them so the air can circulate.

They need sunshine...rain here once again....