Unpruned raspberry bushes won’t yield more berries and can lead to problems and even early die out of the raspberry bushes. Pruning raspberry plants does more than just keep your plants under control. Raspberries can be prone to disease and pruning inhibits the spread of disease throughout your patch. To insure that light and air can get inside the plants and to facilitate pruning, keep your raspberry plants controlled in a row. Prune all canes that bore fruit last year; they won’t fruit again. These will have grayish, peeling bark. Remove any canes that have grown outside the 12 – 18 inch designated row footprint. Keep reading the tutorial in the source.