Summary

The greater wax moth Galleria mellonella is estimated to cause upwards of $5 million worth of damage a year in the United States alone.

The adult wax moth is greyish brown and has a wingspan of around 3 cm. The adult female moth penetrates the hive and lays her eggs directly on the comb. The wax moth larvae feed on the wax, the pollen, and even, if there are many larvae, on the host's brood.

Vita has a biological wax moth treatment B401.

Life Cycle

The moth life cycle consists of four stages. The first stage, the egg, is tiny and, unless specifically searched for, generally goes unnoticed. Eggs are usually laid in cracks between hive parts in batches of up to 300.

In five to eight days, wax moth eggs hatch to the second, larval, stage. Larvae burrow into the beeswax comb and feed for one to five months, depending on the temperature. Fully-grown larvae have a dark, hard head capsule, three pairs of segmented legs, and several body segments. They are initially white, turning dark grey with age, and about 2 cm long.

Wax moth larvae live on impurities in the comb (rather than, as their name suggests, the wax itself), and so prefer to live on comb that has been used for brood rearing. Foundation is rarely consumed, but in capped honey, young larvae tunnel just below the cappings, which causes harvested honey to leak, and comb honey to become less attractive.

Fully-grown larvae form cocoons either in the comb debris or, more commonly, attached to the frame or hive body. Larvae chew cavities in which to cement the cocoons, and lasting damage is done to the frame.

Adult wax moths have acute sensory capability to find and exploit beeswax. They readily enter beehives to lay eggs, but the bees keep their numbers under control. Adult wax moths have atrophied mouths, do not feed, and so cause no damage. Adult wax moths and larvae can, however, act as vectors for the transfer of serious bee diseases such as foulbrood.

Since wax moth numbers are kept under control by healthy colonies, it is in weakened or abandoned hives, or stored frames, that populations explode. In this case, all four life stages can be found, along with tunnels of silk throughout the combs, and deposits of dark faecal matter. Very quickly, all that will remain is gritty debris of comb remnants on the bottom board, and cocoon attachments. Little or no comb survives intact after a wax moth infestation.

Control Of Wax Moth

IN COLONIES

Although beekeepers may claim wax moths are responsible for killing their colony, they are not capable of overcoming a healthy hive. However, if a colony has become weak, and especially if the queen has been lost, the population may dwindle to a point where there are no longer sufficient numbers of bees to protect the combs. In favourable conditions, wax moth can completely destroy brood comb in under a month.

Ensuring active and populous colonies is key to preventing their infestation by wax moth, but other measures should also be taken. Keeping the hive (especially the bottom board and in cracks and crevices) clean and free of debris, and allowing bees access to all parts of the hive, can help reduce damage by removing places where wax moths can become established.

IN STORED COMBS

Removal and storage of drawn comb (particularly in warmer temperatures) increase the risk of infestation. Trying to protect comb within plastic bags can be ineffective since eggs could already be present. Similarly, storing outside is only an effective strategy when temperatures are consistently below freezing throughout the storage period.

The natural microbial bacteria Bacillus thuringiensis offers highly effective protection against wax moth. The Vita product B 401 (also known as Certan) is a concentrated solution of B. thuringiensis, which offers up to 100% efficacy.

References:

Caron, D. M. (1992). Wax Moth. American Bee Journal, Vol. 132 (10): 647-49, USA.

Charrière, J.-D.; Imdorf, A. (2004). Protection of honey combs from moth damage, Communication nr. 24, Swiss Bee Research Centre. Bern.