If you are pruning, and wondering whether you can protect pruning wounds from infections by trunk diseases, there is a supplemental label of Rally for control of various trunk diseases (Botryosphaeria, ESCA, and Eutypa).  Also we have a special use label of Topsin-M for VA.  

You can apply them with a sprayer or as a paint.  It would be a very good idea to use them, especially when you are making a big cut.  The timing of application would be soon after pruning and before a rain.

Also, double pruning (early winter rough cut followed by the final cut in early spring) showed to reduce 95% of trunk disease in a CA study.