Traditionally, damage by wax moths (generally the greater wax moth, Galleria mellonela) has accounted for large losses of stored comb. This is especially in the southeastern and southwestern United States, where warm temperatures ensure a viable wax moth population year around. The larval stage of the wax moth does damage by boring into and leaving silk-lined tunnels or galleries in the combs, in extreme cases, the comb is reduced to nothing more than a mass of web. Larvae will also bore holes in the wooden parts of the hive.
It is emphasized that the wax moth is generally not responsible for the death of a colony. Rather this insect is a "garbage man" of sorts, moves into areas unprotected by worker bees, and can be an early warning signal that everything is not well with a colony. Strongly populated honey bee colonies always have wax moths, but are unaffected because the moth larvae are being continually sought out and then cast out of the hive. Only when a colony becomes weak in numbers because of disease, starvation or some other occurrence, does the wax moth move in to "clean up" the colony by consuming the comb.
Wax moth is a consistent and vexing problem in stored comb; the rate of moth development in a stack of stored supers rivals the imagination! Traditionally, stored comb has been either heated, cooled or fumigated with chemicals to deter wax moth infestation.
A bacterial disease spore, which attacks only wax moth larvae, is now marketed under the name Certan for control. This material represents a breakthrough because the disease is so specific it cannot harm either bees or people and can be used with little concern around bees or equipment. However, its application is labor intensive and not favored by large-scale operators. Several chemical fumigants that have been used in the past were methyl bromide, aluminum phosphide, ethylene dibromide (EDB) and paradichlorobenzene (PDB). At present, only aluminum phosphide and PDB are approved in Florida.
Of these, paradichlorobenzene is less dangerous to the applicator and easier to apply. Unfortunately, it does not kill all stages of wax moth and so remains more of a preventative; it will not clean up a severe case.
Again, it is advisable to buy any chemicals for beekeeping use from bee supply houses; this way full information on use of the substance in beekeeping is available. All pesticides must be labelled for use on stored comb; the label is the law, under no circumstances should a pesticide be used, if that use is not specified on the label. Beeswax is similar in structure to many insecticides and often has an affinity for these substances. As a consequence extreme caution should be exercised when using pesticides anywhere near a beekeeping operation. For further information on toxicity of pesticides, see Florida Cooperative Extension Circular 534 , Protecting Honey Bees From Pesticides.Table 1 is a chart of temperatures required to kill all stages of wax moth using cold or heat treatment as published in Farmers' Bulletin Number 2217 "Controlling the Greater Wax Moth..A Pest of Honeycombs," USDA Science and Education Administration, 1981.
Care should be taken when treating with cold because beeswax becomes brittle and breaks easily. Even more caution, however, is advised when heat-treating combs. They should only have very little honey to avoid distorting the wax comb, must be placed vertically in supers and the heat must be circulated to avoid creating hot spots which could melt the comb. Consult referenced works for more information on wax moth control. http://edis.ifas.ufl.edu/AA090