From _Honey_Bee_Pests,_Predators_and_Diseases_ (Morse and Nowogrodzki):
 
"If artificial cold is used, the following minimum treatments are
required to kill all stages of the greater wax moth: -7dC (20 dF) for
4.5 hours, -12 dC (10 dF) for 3 hours or -15 dC (5 dF) for 2 hours..."
 
Temperature less severe in natural environs allow wax moths to survive
over the winter.  I believe it is the pupal atge that is most hardy,
but this is my recollection which has been noted to be flawed.
 
Aaron Morris