Wisteria is very invasive. It took me years to kill out mine after it's roots spread from one side of my yard to the next, and then proceeded to go through a crack in my neighbors foundation and pop up in his bathtub drain. Just because I want to be a good neighbor I would never replant Wisteria in the ground again.

"I've also heard wisteria can be very hard to get rid of" In zone 10, dry warm Mediterranean climate, wisteria is IMPOSSIBLE to erradicate. Ask me how I know... Plant it REALLY FAR from anything that matters and be prepared for a life long battle to keep it in bounds. At least here, that's how it goes. Beautiful vine, but I would never plant another unless I had the acreage for it not to tear anything down. That means more land than I will ever be able to afford. Eduarda

I don’t grow Blue Moon and am in a warmer area than you. But we have grown both a Chinese and a Japanese wisteria - both are kept pruned to grow as ‘trees’ (click on the picture in the round circle by my name to see them...) The Chinese one was planted in 2000 and the Japanese one about 7 years later. The flowerbuds sometimes winterkill, but the vines always survive here. The Japanese one is the most vigorous re root suckers - it still regularly produces dozens of them; the Chinese one hasn’t produced any in quite a few years. The Japanese one also produces a LOT more of the whippy new stems from the main framework than the Chinese one does. The Japanese one requires root sucker removal and trimming back excess top growth almost weekly while the Chinese one can go a couple of weeks now between prunings. The Chinese one will produce secondary summer flowers near the site where new growth was cut back about 7-10 days after cutting the growth back. By the sounds of it, Blue Moon’s growth habit is somewhere in between.... Definitely that lattice will get mangled! We once visited a garden in the Niagara area where wisteria had been let to grow wild. An interesting thing they did in a few places was to use the long flexible stems to actually weave walls in places! If you’re growing a wisteria and want to control it well, in our experience pruning can be almost a daily chore at first and will always be a regular chore...! But pruning is what maximizes flower production, so prune, prune, prune....

Interesting issue.... Based on the clockwise twining seen in your pictures, this appears to be a Japanese wisteria. Is is a named variety/grafted plant? Does it produce a lot of root suckers and, if so, do you allow them to remain and climb on the structure? You said in your original post that the vine is doing well - is any part of it visibly dead - i.e. no leaf or flower growth? Does the vine lose its leaves at some point in the year in your climate? (My two wisterias are just losing their leaves for the winter now....) If the vine loses its leaves at some point in your growing season, that's a good time to give it a close inspection. Since the support structure is also wood, it may well have rot too, so check it carefully (What kind of wood is the support structure?) Wisterias are pretty tough plants that can survive a lot of damage. If it is still producing healthy new growth from the stems that have split, I wouldn't worry too much about the vine. If there are areas where the vine is dead (i.e. no leaf or flower growth) I'd prune out the dead section and let nearby healthy growth fill the blank space. If there are suckers from above a graft union or if you normally let root sucker grow and they flower the same as the rest of the vine, you could use them to help fill in any dead sections too. If there is a nearby botanical garden or a commercial grower of the vines, you could ask them for further help in identifying the source of the problem and what to do. At this point, I wouldn't give up or the vine or assume it will die out. They are very tough plants and it would take a lot of damage to completely kill it! Do you have a picture of it in flower on the structure? If so, I'd love to see it....