What the heck is wrong with my raspberries?!
This is the third year of a new row of raspberries. I started with six or seven small starts the first year, which grew and multiplied well, so the next year I had quite a few good healthy canes. This year I have a full thirty foot row and last year's canes are blooming well and producing quite a few berries. The problem, though, is the berries are mostly very small and they fall apart (or crumble) when we pick them. The berries are in a raised box against a concrete wall in a bed where raspberries grew about fifteen years ago. The berries in the back are larger and less crumbly. The leaves on the bearing canes are yellowing somewhat, which I think is what my berries always used to do. The new growing canes are huge and healthy, although I have seen a few whiteflies around the bushes.
I did a little research and see that this might indicate the presence of a virus. Does it sound like that to you experts, or are there other reasons for berries to turn out this way (like maybe too little water?)? We have used Miracle Gro to fertilize, and only once every few weeks. Any ideas?