Ms B, not to highjack your thread, but I have he same problem. I can't wait to hear what the problem is.

I grow everbearing red raspberries here in Madison, Wisconsin. I think the variety is Heritage, and the patch must be 15 years old. Every fall, I cut the canes down, clean up any weeds, and mulch the area with shredded leaves from our Norway maple tree. The refuse goes on the compost pile, and slowly works its way down to the pit under the heap. So far, I am not having virus symptoms. However, the symptoms you describe are common in older raspberry patches, and are thought to be due to a virus infection. I have seen recommendations to cut down the infected canes, burn them, and plant new stock at a new location. That is not a practical solution for everyone, since we have limited yard space, and the original reason for locating the raspberry patch in a specific spot still exists. In your situation, I would consider digging out the raspberries, amending the soil with peat moss and agricultural sulfur, and planting blueberries. Lowering soil pH to 4.5 might drive the nematodes away, and any residual virus would be rendered not infective.

I can't see how changing out raspberries would make any difference. Suckers are essentially new plants.
Could the issue be soil depletion?
Shriveling fruit sounds like a watering issue.

If you have a virus the new plants will pick it up too.

I suspect that the least expensive way to nail the diagnosis would be to plant a new variety of raspberries in the same spot, and await the outcome. If the issue with small and crumbly fruit goes away, then it likely was not a virus that caused the problem. I suspect that there is a virus involved, and that the new raspberry bed will be adversely affected, as well.

Is there any way you could remove all evidence of the old patch and wait one full year before you plant the new patch? If it was my yard I would dig as much of the soil up as I could stand to do and then make that entire area a giant compost pile that I stirred as often as I could. And then replant a year later in the composty soil.

I think that with some viruses you will just have to replace plants every so often - they are not just coming to your berry plants via the soil but through all the plants in the surrounding area. Plenty of fruit diseases live all over the garden but mainly affect one type of plant - so, new plants will get infected by other plants that may not be showing you signs of the virus.

It's common with cane fruits to accumlate viruses over time. From what I've read on various extension resources, the recommended treatment is to pull up the raspberry bed and grow something else in that spot. The above recommendation to grow blueberries is a good suggestion - higher pH would kill off the viruses and ensure they don't spread. Raspberries are pretty tolerant of poor soil and even a bit of shade, so unless you're very pressed for space, you can likely find a new spot elsewhere for a new planting of raspberries. You could also dig out most of the soil, compost heavily over the spot (make a hot compost on the site, if possible), put in beneficial nematodes once it cools down and then replant in the same spot.