I've been
growing raspberries for years now. I don't really have any problems with my "everbearers". I've actually converted them into "oncebearers". I noticed that the fall crop was much larger and of much better quality than the summer crop, so I now prune all the canes to the ground in the winter so as to put all the energy into the fall crop. I now have no summer crop at all as the summer crop produces on the previous years growth.
I was having problems with my "oncebearers". They were starting to have pretty extreme dieback. I decided they were suffering from raspberry cane borers, so last
spring I watered heavily with Dipel in
spring. Unfortunately, I still had considerable dieback, but mainly of a different sort. We had hard freezes on 5 consecutive nights back in April. The dieback from the borers however, seemed to be substantially reduced.