Question
I live in central OH and I have a wisteria that has been growing over an arbor for many years. Currently the main trunk is 6-8in in diameter. In the summer the foliage is thick, green and healthy. Some years it blooms some not but not a concern. The problem I'm having is a white looking fungus that forms on the bark and eats into the plant  bark leaving a dead, rotted and hollow limb. I've try various fungicides with no results. Currently the plant foliage covers an area of about 20ft x 15ft.  Can you help please? I love this thing and will do anything to save it... Thanks for your time

Answer
Hi Dan -
I am glad you've been enjoying one of my very favorite flowering vines.  You did not say whether the vine is Chinese or Japanese wisteria, but it probably doesn't matter too much. What is of concern, of course, is the white fungus that has shown up on the bark. (You haven't noticed any fungus on leaves, right?)
I'd love to see some photos of the problem, but absent any visual aids, I would venture that your wisteria has what is commonly called "white rot," which is a fungal disease that is known to be resistant to many fungicides.  Most people deal with it by pruning away affected limbs, but it sounds as though that would practically decimate your wisteria!  Fungus can spread very easily - through rainfall, contaminated pruning shears, and even wind-borne spores. Have you applied the fungicide via spray or through a systemic (soil drench applied to roots)?  Systemics are, in my opinion, more effective than sprays.  I am usually reluctant to recommend actual brands, but Organocide Plant Doctor formerly Exel LG) might help.  One final note: Wisteria's "life span" is not usually measured in many decades.  Do you know how old your vine is?  Most wisteria live only 15-30 years, and as they age they are more susceptible to fungus and other maladies.  
Dan, I wish I could be more helpful. Unfortunately, there is no "magic bullet" for many fungi, particularly those that are well-established.  Let me know how things go, please.  I feel your pain.