It is summer in Australia. It does not have gall. Some roots were cut last week for paving.
My Wisteria Is Dying..Leaves Are Yellowing and Drying Up
Certified GKH Gardening Expert
The cut roots are likely the issue, especially if the tap root was cut or damaged. The plant is trying to reduce its size to something the roots can still support. I would recommend a heavy pruning of the wisteria vine so that it better matches the current root system. Also, follow the steps in this article for treating transplant shock. It is currently going through something similar to transplant shock: