Hello,

This winter I have hard pruned my wisteria.
I am training it for a future bonsai, using the cut-and-grow technique.
I did not use any cut paste on the wounds.
During winter, I have sprayed the trunk (and probably the wounds too) with diluted lime sulfur for pests control.

Now, in spring, the wisteria is creating buds. But the wounds, have some black marks/dots.
Is it fungus? Should I treat it with something? Should I be worried?

 

Looks normal to me nothing wrong with it assuming it is alive.

I second Geoff. Just leave it to recover. Some trees make it, others don't.

next time, use wound paste if you make large cuts

There will always be someone who has to be negative about a product. Cut paste works and works well. I use it all the time, if you watch any Japanese videos on Youtube you will see that they always use it and that is good enough for me.