What would be the correct chemical to get to combat wax moths?
I think your best bet would be BT (
Bacillus thuringiensis) spray. It's not a poison ("chemical") but is very effective. It has a long lasting effect since the spores of the BT remain in the hive, thus providing protection against new generations of moths. It is harmless to the bees and can be applied while the supers are on the hives just as well as when they are stored off the hives.
My general practise has been to spray the frames with BT after the honey is extracted and then put them back on the hives for cleaning. As the bees clean the remnants of honey, they also spread the BT sporess to unsprayed parts of the hive, expanding the protection to unsprayed areas.