Here is my previous email:

It's hard to diagnose from just one photo, so here's a link to a publication on raspberry diseases in Michigan. I have a feeling that you can narrow down what is attacking your plants.

It sounds kind of like you might have cane blight. It says "On infected second-year canes (floricanes), the side branches may suddenly wilt and die, usually between blossoming and fruit ripening. Upon close examination, the presence of dark brown or purplish cankers can be observed on the main cane or branches below the wilted area." Here's a University of Wisconsin publication on cane blight with photos.

Have you observed galls on your plants? If you dig down, do you see a gall or galls at the crown or on the roots? Here is information on bacterial crown gall from OSU.

Once you have taken a look at these resources, if you are still unsure of what is going on or you have additional questions, please feel free to reply.

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It's hard for me to tell if the plants have galls because they have been dead for a long time. The cane on the left in the photo might have had a gall, but it is dried up and hard for me to see. I would look at some of the healthier canes and see if they have galls forming at the soil line.