It could be caused by several things. It might be stress if there have been up and down weather changes this year. It could also be getting too much water. Sometimes too much water will cause a fungus as well.
If the branches aren't dry and dead, then chances are it will come back; but if there is a problem with the root, then I'm not sure.
Mine are about 30 years old and I've never fed them anything nor have I treated them with anything, so I don't know how they would react to Dyna Gro. I guess I'm not much help.
Zuzu has gorgeous Chinese wisteria and she lives in California. Hers grow over two old trees, so she might know more about problems with them than I do. Mine is Kentucky wisteria, aka American wisteria and you can see it here:
http://garden.org/ideas/view/S...
There's nothing in my article that will help with your problem, though.
I love wisteria, so good luck with yours. I'm hoping it might only be stress related and will quickly recover.
