My wisteria vine is old and was planted before my ownership of the home. It has two major problems. It is diseased with white patches and the base of the trunk is half missing due to decay or injury. I've pruned half of the plant and is destined for removal in two weeks if I don't save it. I love the vine, but I need advice of how to save it. It has a strong wooden structure to grow on and the soil drains; and this year it bloomed beautifully.
Certified GKH Gardening Expert
Unfortunately, it sounds like it may have crown rot. The white patches are likely lichen, which are more of a side effect of the ill health of the plant. They tend to attach to woody plants that are dying. This article will explain more about crown rot and does have some suggestions on how you might be able to help your vine: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74133.html