By Lgf
United Kingdom 
Hi
I've just checked my raspberry canes and have found that the underside of leaves on most canes are partially covered with a black powder, which looks like the kind of mould you get on windows as a result of poor circulation. I've searched and can't find this condition listed as a typical raspberry problem. I presume it is a fungal disease, am I right and how do I treat it? Thanks
17 Nov, 2012
Answers
My garden is increasingly sheltered, and my raspberries still have most of their leaves on. They will fall off by New Year, so any mould on them now if not really an issue, though to be safe do not leave the fallen leaves around the base to stop the mould reinfecting.
17 Nov, 2012
Why worry? Half the plants in the garden and in the countryside around us are covered in black, grey or white moulds at this time of year. It's part of nature's way of dealing with dead and dying material at this time of year. As long as the canes put up new healthy growth next spring you have no need to worry.
17 Nov, 2012
I'm surprised you have any leaves on your raspberry canes at this time of year - ours shed their leaves a good month ago.
17 Nov, 2012