Powdery mildew and composting

My comfrey has been neglected and not been cut.  It is. Now very tall and has powdery mildew.  I've cut it down and there are new shoots appearing. Should I bin the prunings or compost them?  Has anyone else had this problem?

I think, but correct me if I'm wrong, that powdery mildew is not a cause for NOT composting them. It doesn't spread like that

I would agree with Sarriss, I think different plants have their own version of mildew and would definitely add to the compost or use them to make a feed for your plants.

Thanks will do