Blackberry psyllid (Trioza tripunctata) is an unusual pest of blackberries and uncommon enought that most growers will never encounter it. However, when they do feed on blackberries, their damage is showy enough to attract a lot of attention. As few as one adult psyllid can cause the characteristic cane shortening and leaf curling, which is an aggressive plant response to psyllid feeding. I have described this injury as making canes look like broccoli or mushrooms.
I posted a description of blackberry psyllid biology along with images of immature psyllids in 2010. Blackberry pyllids spend the winter in pine trees, and as a result, they are most common in plantings near pines. Because they are so rare, there are no recommended mangement programs for blackberry psyllid. In most instances, infesation is likely low enough that cultural control, pruning away damaged canes, is likely sufficient.