We have a beautiful wisteria that has quit leafing and I think it may be dying. Last year, we had a sewer leak discovered in our backyard. The leak appeared to be brown water from our laundry and we noted the smell of laundry detergent in the run off water. We had the leak located and fixed last June (it was about 4 feet from our wisteria) and we noticed later in the summer that our wisteria had very puny leaves, but a lot of seed pods. This spring I have noticed that the wisteria vines are dead in some places and there is no leafing yet. When I looked at the plant base, I notice that the exterior bark is peeling off and vertical cracks are forming up the trunk of the plant. The bark we pulled off is crumbly and looks like it rotted or had water damage. I am concerned that our sewer leak may have affected the wisteria's root system and potentially killed it. I'd like to know what I can do to diagnose the program and how I can keep it from getting worse.
From your description, it certainly sounds like your wisteria is suffering from a severe root rot caused by the sewer leak. Sad to say, you may well have lost the plant. First, try to see if there are any living branches or trunks. Live branches will be flexible when bent, dead ones will snap. Scrape some bark off the trunk in various places - if there's green tissue underneath, there is still some life in the tree. Dig around the roots to see if they are brown and mushy, or if they have any live tissue (scrape test.) This article has some more info on root rots: https://www.gardeningknowhow.com/ornamental/vines/wisteria/wisteria-diseases.htm
If there's any life in the roots or the trunk, you may be able to save the plant by cutting it back severely, digging it up and planting it in another spot.