Key points
- Two moths whose caterpillars eat wax: the greater (Galleria mellonella) and the lesser wax moth (Achroia grisella).
- A strong colony defends itself; weak colonies and stored combs are the real targets.
- Cold is the main weapon: freeze combs, then store them cool, dry, in the light and with airflow.
- Avoid paradichlorobenzene and improvised fumigation: they leave residues in wax and honey.
- Larva with prolegs and silk: wax moth. Spiny larva, no silk: suspect small hive beetle and report it.
Wax moth is a pest, not a disease. Two night-flying moths lay their eggs in hives, and their caterpillars feed on wax, pollen, debris and the pupal skins that build up in the combs. In a strong colony, workers find and remove eggs and young larvae, and the problem stays invisible3.
A weakened or dead colony, and above all the drawn combs stored after harvest, can however be reduced within weeks to a mass of silk and droppings. Most of the fight therefore takes place in the storage room.
Two species, one way of life
The greater wax moth (Galleria mellonella) is the more destructive. The female averages 15 to 20 mm long with a wingspan of about 31 mm, and the male is smaller. Larvae reach 25 to 30 mm when fully grown1. Adults do not feed; females live about 12 days and males about 21 days1, 2.
The lesser wax moth (Achroia grisella) is smaller and less damaging. The adult is silvery with a conspicuous yellow head: males are about 10 mm long, females about 13 mm2. Its larva reaches about 20 mm4.
A life cycle driven by temperature
The moths are nocturnal and most active on warm summer evenings4. The greater wax moth female lays clusters of 50 to 150 eggs in cracks, about 700 on average over her life; the lesser wax moth female lays 250 to 3002.
The length of each stage varies enormously with temperature1, 2:
| Stage | Greater wax moth | Lesser wax moth |
|---|---|---|
| Egg | A few days at 29-35 °C; about 30 days at 18 °C | 7 to 22 days |
| Larva | 6 to 7 weeks at 29-32 °C; from 28 days to 6 months depending on conditions | 6 to 7 weeks at 29-32 °C |
| Pupa (cocoon) | 6 to 55 days | About 37 days |
| Adult | Female about 12 days, male about 21 days | Female about 7 days, male about 13 days |
Development is fastest at around 29 to 33 °C, as in a hive in season or an attic in summer; the greater wax moth can then complete four to six generations a year1. In cold climates it overwinters as a mature larva or pupa4. A cool room therefore already partly protects combs.
Damage
Tunnels and silk
Greater wax moth larvae tunnel through combs down to the midrib, lining their galleries with silk and leaving grainy black droppings2. At an advanced stage, only a felt of silk and debris remains.
Cocoons and gnawed wood
Mature larvae settle against woodwork to pupate. They gouge boat-shaped hollows into it and attach their tight white cocoons there2. In heavy infestations, cocoons cluster along top bars and box walls, weakening the equipment.
Bald brood and galleriasis
Lesser wax moth larvae, and less often greater wax moth larvae, tunnel just beneath brood cappings. The result is lines of uncapped pupae across several adjacent cells: this is bald brood. The linear pattern distinguishes it from hygienic behaviour, which opens scattered cells2.
Silk can also trap young bees, which uncap their cell but cannot get out and die in place: this is galleriasis1, 2.
A “cleaner” in nature
In the wild, wax moth quickly destroys the combs of dead colonies5, which frees the cavity for a new swarm. Some authors describe it as a colony symbiont, present at low levels in healthy nests2.
But it disinfects nothing: spores of Paenibacillus larvae, the agent of American foulbrood, have been found in its droppings, and bee viruses in its larvae1. A colony that died of foulbrood is an outbreak to deal with, not something to leave “to the moths”.
Recognising it and avoiding confusion
Silk tunnels, grainy black droppings, cocoons stuck to woodwork, fast-moving greyish-white larvae: the signs are easy to read. In a populous colony, a heavy infestation almost always points to another problem: queenlessness, starvation, disease or poisoning3.
The confusion to avoid is with the small hive beetle, Aethina tumida, a regulated pest2, 9:
| Criterion | Wax moth | Aethina tumida |
|---|---|---|
| Mature larva | 20 to 30 mm, greyish white | About 1 cm, creamy white |
| Legs | Three pairs at the front plus prolegs under the abdomen | Three pairs at the front only |
| Back | Smooth | Rows of spines |
| Silk | Silk-lined tunnels, cocoons | No silk |
| Honey | Little affected | Ferments, runs, smells of rotting oranges |
| Pupation | Inside the hive, cocoon stuck to woodwork | In the soil, outside the hive |
| Status in France | Not regulated | Must be reported to the DDPP |
If in doubt, keep a larva in alcohol and see the Small hive beetle factsheet.
Regulation
In France, wax moth is not a regulated health hazard: no notification is required. Products used against it, however, fall under biocide rules: only a product authorised for this use may be applied. Authorisations vary between countries and change over time.
Prevention in colonies
- Keep colonies strong, with a laying queen: no treatment exists for use in an active colony3, 8.
- Match hive volume to the population: unite weak colonies, remove combs the bees do not cover.
- Renew combs: old dark combs, rich in pupal skins and pollen, are the ones larvae seek out.
- Remove dead colonies and their combs promptly.
Protecting stored combs
Cold and freezing
The reference method, freezing kills all stages, eggs included, without residue. Lethal durations once the wax is at temperature2, 4:
- 2 hours at -15 °C;
- 3 hours at -12 °C;
- 4.5 hours at -7 °C.
These times apply to the core of the comb. A full super takes a long time to cool: practical guides therefore recommend at least 72 hours in the freezer3. Frozen wax is brittle: handle it carefully.
Freezing does not protect against reinfestation: afterwards, store combs out of the moths’ reach, in sealed or wrapped stacks4. A cold room, by contrast, protects them for as long as they stay there.
Heat
The published durations are 80 minutes at 46 °C or 40 minutes at 49 °C2. Above that, wax softens and sags: a well-regulated hot room is needed.
Light and airflow
Light and air movement discourage egg-laying. A bright, ventilated room with supers stacked criss-cross reduces attacks markedly3, 4. Pale super combs, free of pupal skins and pollen, attract few larvae, unlike brood combs.
Bacillus thuringiensis aizawai
Bacillus thuringiensis produces a protein that is toxic to caterpillars and harmless to bees. Sprayed on combs before storage, it kills young larvae that eat the treated wax4, 7. The product long sold in Europe, B401, is being discontinued by its manufacturer, which cannot supply the data required under current regulations6. Its successor, B402 (Certan), is sold in North America but, according to the manufacturer, not in the EU. In Switzerland, Mellonex is no longer on the market5. Before buying, check that a Bt product is authorised where you live.
Sulphur: a historical method
Burning sulphur strips in closed stacks of supers was long common practice. The gas released is toxic to the user, the fire risk is real and residues are possible1. In Switzerland, sulphur, formic acid and acetic acid are not permitted against wax moth because they are not approved as biocides5, 10. In France, check the status; if in doubt, use cold.
Products to avoid
Paradichlorobenzene (mothball crystals) was used for decades. It does not kill eggs, and residues have been found in honey and recycled wax: it is banned for this use in Switzerland1, 5 and has no place in a honey house. Naphthalene, methyl bromide, phosphine and other fumigants are toxic to the user and to bees, and leave residues1. Carbon dioxide in an airtight enclosure is the only fumigation the Kwadha et al. review considers recommendable1. Essential oils are not registered against wax moth4.
In practice: what beekeepers actually do
Wax moth is mostly managed between harvest and putting the supers back on. Here are the most common practices.
Sort before storing
- Most beekeepers split combs into three batches: pale super combs, brood combs still in good condition, and old dark or damaged combs.
- Old combs go for rendering straight away: keeping them means feeding the wax moth.
- It is common to let the bees lick supers clean after extraction, then to store them dry.
Freeze what is at risk
- Brood combs, combs containing pollen and any comb showing larvae go into a freezer or cold room before storage.
- Many work in rotation: one chest freezer, a few days per batch, then straight into sealed boxes.
Stack and store
- Supers of pale combs are often stacked criss-cross in a dry, bright, ventilated room, safe from mice.
- Frozen combs, by contrast, are stored in sealed stacks: queen excluder or board at top and bottom, joints taped or a plastic cover, to keep moths out.
- Stacks stand on pallets, never on the floor or outdoors.
Typical calendar in a temperate climate
- July-September, after each harvest: sort combs, let bees lick them clean, freeze at-risk batches, store immediately.
- September-October, wintering preparation: remove surplus combs from colonies, unite weak colonies.
- Winter: check stacks; little risk in an unheated room.
- Spring: check stacks as soon as it warms up; any suspect comb goes back into the cold.
- Before supering: final check; damaged combs go for rendering.
Most common mistakes
- Storing combs in a warm, dark attic or shed: ideal conditions for the moth.
- Keeping old dark combs “just in case”.
- Freezing combs and then leaving them in the open, where they are laid on again.
- Using mothballs or household products: lasting residues in the wax.
- Leaving a dead colony in the apiary, where it feeds wax moth and attracts robbing.
Frequently asked questions
Can wax moth kill a strong colony? Rarely. It mainly finishes off colonies that are already weakened: look for the underlying cause.
Are pale super combs at as much risk? Less, but they can still be attacked, especially next to brood combs or in a warm room.
Can a damaged comb be saved? If the damage is limited, freeze the comb, then give it to a strong colony, which will clean it up. A comb reduced to silk goes for rendering, and the wood is scraped to remove the cocoons.
References
- Kwadha C.A., Ong'amo G.O., Ndegwa P.N., Raina S.K., Fombong A.T. (2017). The biology and control of the greater wax moth, Galleria mellonella. Insects 8(2): 61. doi.org
- Ellis J.D., Graham J.R., Mortensen A. (2013). Standard methods for wax moth research. The COLOSS BEEBOOK, Vol. II. Journal of Apicultural Research 52(1). doi.org
- Jack C.J., Ellis J.D. (2021). Wax Moth Control. UF/IFAS Extension, publication ENY-121. edis.ifas.ufl.edu
- Perennia (Nova Scotia). Wax moth fact sheet (French edition). perennia.ca
- Agroscope, Swiss Bee Research Centre. Wax moth control. agroscope.admin.ch
- Vita Bee Health. Wax moth control product to be superseded (B401 replaced by B402). vita-europe.com
- US EPA (2020). First beehive uses of the currently registered active ingredient Bacillus thuringiensis subsp. aizawai strain ABTS 1857. epa.gov
- FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.
- Neumann P., Elzen P.J. (2004). The biology of the small hive beetle (Aethina tumida, Coleoptera: Nitidulidae): gaps in our knowledge of an invasive species. Apidologie 35(3): 229-247. doi.org
- Food Safety and Veterinary Office, Canton of Fribourg (2026). Cantonal apiary inspectorate information for 2026 (in French). fr.ch
- USGS Bee Inventory and Monitoring Lab. Wax worm, U, Maryland, side (public domain). usgs.gov