If it was cane borers, the canes would have an obvious limp bend near the tips and a dark place near the bend where the borer eggs was deposited. Look here http://www.extension.umn.edu/yardandgarden/ygbriefs/e216raspberry.html and here http://ipm.illinois.edu/ifvn/volume16/frveg1601.html (photos about 2/3 down the page.)