Dear Stephen,

It sounds like you are sure that cane borers are your problem but I've provided a link to a Cornell University blog page that has great photos if you want to be sure.

https://blogs.cornell.edu/berrytool/raspberries/raspberries-cane-borer-girdler-and-rednecked-cane-borer/

If you don't yet have the problem, it is recommended that you remove any wild raspberry patches in the vicinity of your plants if you can as they serve as a source of the borers.  There does not seem to be any specific way to keep them away but the insect has a two-year life cycle and therefore the populations can be kept in check with routine surveillance and removal of any infected canes as noted below.

If you do already have them in your patch, regular pruning of infested canes several inches below the lower 'ring' (the punctured line that the female makes above and below the egg site) should keep the population in check.  You want to be sure to dispose of the infested canes as far from your growing site as possible.  

I've attached a very nice handout from NH University Extension as a reference for you.

Good luck with your raspberry patch!