Dead raspberry plants
What are the possible causes of several plants dying even when they seemed to be thriving by leafing out? Some died after pruning.
Washington County Oregon
There could be many causes for raspberry plants dying even as they are leafing out in spring, including fungal root rot, boring insects etc.
Probably the first place to look would be the roots. Pytophthora root rot (Raspberry - Root Rot https://pnwhandbooks.org/plantdisease/host-disease/raspberry-rubus-spp-root-rot) could cause dying canes. With this disease you will see dark rotted roots without nice white fibrous roots. Since the roots don't function, the canes die. Soil drainage is key to preventing this disease, because the phytophthora organism requires water to function. To prevent this disease use certified disease-free, phytophthora resistant planting stock. Plant in well-drained soil that has not grown any berries for several years. Planting on beds raised 12 inches above the soil line will improve drainage considerably. Fungicides are really not effective. There are also other soil fungi that can cause root rot in raspberries.
Insect pests that might cause cane death include crown borer. The caterpillars live inside the crowns and canes, so you need to open up the canes to find the caterpillars.
This article gives excellent information and advice on Growing Raspberries in your Home Garden https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1306.pdf. If you send more information, like how many of your canes were affected, how long you have had the raspberry plants, how the other canes are doing - are you harvesting raspberries from them, pictures of your raspberries, and any other questions you may have we can narrow down the causes of your raspberry problems.