The long straight cane is next year's fruiting wood. Whatever you do don't cut it off. Tie it in to the wires. When your current year's fruit has been picked cut down the canes which fruited this year.

Thanks for the unambiguous answer! I am going to tie that thing up right now before it gets any thicker.

Thickness is already established at any one point on a growing cane, except where the new leaves become smaller near the tip. Unless you want to climb ladders next year, prune the top off at a convenient height and force branches to grow.

If you can get the cane to bend you can tie it horizontally or at an angle. Do you have several parallel wires? If so you can tie one cane to each wire. That will also promote side shoots. You could also tip it. (ie cut the tip off) When I said don't cut the cane off I meant don't remove it. You can shorten it. The main message is to understand that the new cane is needed for next years fruit. If you Google training blackberries you'll find lots of diagrams.

I cut mine off when it was reaching for the roof on the porch and it branched out below the cut with 4 more canes and sent up 2 more skyscrapers from the root that are at least 8-10ft.and arching since they weren't cut.

Many say to pinch back the tips after it gets to be a decent manageable height (for picking and netting) to encourage branching, create a bushy shape, make it produce more canes and more fruit. I'm picking a basket every other day now there's so many, but the long arching canes have to be picked at dawn before the birds get to them since I cant reach with netting.