Mtssa. Charles M. Fitch Repotting

[estación seca]

If it's new bark dry in the bag, you can put it in a colander and pour boiling water over it. The premixed stuff probably was somewhat moist?

You don't need to spray new medium with anything. It's impossible to sterilize medium without an autoclave or pressure cooker. There are very many beneficial organisms in all growing environments that help keep pathogens in check. Spraying may kill these. It is far more likely preventive spraying is harmful long term.