Should you? It isn't required for any reason. It is optional for vine control only. So if you have room to let them run leave them alone. If not try tying them up to the trellis until the get the idea. :)

Besides when you do prune them that isn't the end of the vine. 2 new vines sprout from the node just below the cut so you end up with even more vines.

A better approach, assuming you planted 3 or more seeds in the hill, is to remove one of the whole plants for better trellis control of the other 2.

Dave

Thanks!