Raspberry tips I removed upon seeing “girdling” on wilted tips
I noticed that the tips of some of my raspberry canes were wilting. Upon inspection the cause became clear. Raspberry Cane Borers are beetles that lay their eggs in raspberry canes, close to the tips. The larva then burrow down the canes eventually killing it. The sign of this is two dark rings (see image above of two affected canes). Hopefully if you remove the tip a few inches below the bottom ring you should be able to save the cane.
Note: I was just shocked to find that there is no wikipedia article on Raspberry Cane Borers because they are pretty well known! Not even a link to a more general class of insects.