From his blog….

The reason the wild ones survive on their own is that they move about. In the garden, humans usually want to keep raspberries corralled in permanent rows. Raspberries are like teenagers: they want to get away from their parents but maintain a connection in case they got in a jam. On black and purple varieties, the new canes that come up in the springtime grow to about five feet high, then bend over in midsummer so that the tips of the canes pierce the soil surface and root. The red and yellow ones spread by suckering, that is new canes come up from the roots moving out and away from the parent plants. By moving away from the old stand every year, the new canes usually avoid disease until they fruit in their second year and then die naturally. (Everbearing reds and yellow canes fruit in the fall of their first year and summer of their second year and then die naturally.)

Understanding this process, the successful raspberry grower sets out new plants in the spring (suckers on red raspberries and the new tip sprouts on the blacks that rooted the year before), at some distance from the old plants, same as they do for strawberries. Setting out new plants at least a hundred feet from the old row avoids diseases or delays them at least. And makes weed control a little easier. Even if you buy so-called virus-free plants, they are not really all that free because virus-free rarely last for very long and is of no help against fungal diseases like orange rust. It does help to cut out the old canes as soon as they are through fruiting, but that is very hard work since they are growing right in among the new canes.