Managing Greater Wax Moth in Beehives: Prevention and Control

If you keep honeybees, you’ve likely encountered – or at least heard of – the greater wax moth (Galleria mellonella). This nocturnal pest is one of the most damaging threats to honeybee colonies worldwide, particularly in warm and humid regions. While adult moths cause no direct harm themselves, their larvae can silently destroy entire combs, leaving behind a mess of silk webbing, excreta, and wax debris. Understanding how this pest works – and how to stop it – is essential knowledge for any beekeeper.

What is the greater wax moth? 🔗

Galleria mellonella, commonly known as the greater wax moth (GWM), is a member of the family Pyralidae (order Lepidoptera). It is a universal pest of both Apis mellifera (the western honeybee) and Apis cerana (the Asian honeybee). The moth is found virtually everywhere honeybees are kept – commercially or by hobbyists – and is especially prevalent across Africa, Asia, and tropical zones worldwide.

Adult moths are slender, measuring 12-20 mm in body length, with a wingspan of up to 40 mm. They are pale brown to grey with reddish-brown mottling on the forewings. Females are noticeably larger and darker than males. Adult greater wax moths have reduced mouthparts and do not consume food or water – their only purpose after emerging is to mate and lay eggs before dying.

Life cycle and behavior 🔗

Understanding the GWM’s life cycle is the first step toward effective management. The moth is entirely nocturnal. Gravid females approach the beehive at night, when the bees are less active, and deposit eggs into crevices within the hive structure. They use hive volatiles – the natural scents of wax, pollen, and propolis – to locate suitable oviposition sites from a distance.

Once eggs hatch, the larvae begin feeding immediately. Larvae burrow into the edges of unsealed brood cells containing pollen, bee brood, and honey, tunneling through to the midrib of the comb. They consume wax, pollen, cast larval skins, and occasionally bee brood itself. The larval stage can last anywhere from 20 days in warm conditions to up to 6 months in cooler environments – with optimal development occurring between 29°C and 33°C, making tropical and subtropical climates particularly high-risk zones.

Larvae undergo 8 to 10 moulting stages before pupating. They bore into wooden frames or hive bodies to spin their cocoons, causing structural damage in the process. After pupation, adult moths emerge ready to mate – and the cycle repeats.

How wax moths damage a beehive 🔗

All the damage in a wax moth infestation is done by the larvae, not the adults. A clear early sign of infestation is bald brood – uncapped brood cells in a straight line or small patch, caused by nurse bees uncapping cells to pursue tunneling larvae beneath.

As the infestation progresses, larvae leave behind masses of silky webs mixed with frass (excrement) and wax debris. This condition is known as galleriasis. In severe cases, the colony may suffer extensive comb destruction and bees may abandon (abscond from) the hive entirely. Combs damaged by wax moth larvae are not fit for human consumption.

Beyond physical destruction, research indicates a further concern: moths can transmit viral pathogens such as Israeli acute paralysis virus (IAPV) and black queen cell virus (BQCV) to bee larvae, adding a disease dimension to what might otherwise seem like a purely structural problem.

Which colonies are most at risk? 🔗

It is important to understand that the greater wax moth is fundamentally an opportunistic, secondary pest. Wax moth eggs and larvae are almost always present in bee colonies, but pose no real risk to healthy colonies because worker bees routinely detect and remove them. Wax moths thrive specifically where bee defenses have been compromised.

High-risk situations include colonies with a failing or dead queen, colonies weakened by disease (such as American foulbrood or Varroa mite infestation), colonies stressed by pesticide exposure or starvation, and hives with a poor bee-to-comb ratio – meaning more comb than bees can actively patrol and defend. Large wax moth populations in a colony typically signal that something else has already gone wrong, and the moths are taking advantage of the reduced bee population.

Stored equipment – particularly stacks of old, dark comb in supers – is another major vulnerability. GWM larvae cause the most damage to dark and stored combs, which are strongly preferred over lighter, newer wax.

Prevention: the first line of defense 🔗

Preventing a wax moth infestation is far easier than dealing with an established one. Most preventive strategies center on maintaining strong, healthy colonies and limiting the conditions that allow moths to get a foothold.

Maintain strong colonies 🔗

The most effective control method is maintaining colonies with a high bee-to-comb ratio and a robust population of young, healthy bees capable of defending every frame. This means keeping colonies queenright, free of disease, and well-nourished. Weak or dead colonies should be assessed and resolved promptly – they quickly become wax moth breeding grounds.

Reduce surplus comb and debris 🔗

Never give a colony more space than its bee population can cover and defend. Remove unnecessary boxes and dead-outs from the apiary as soon as possible, and keep hives clean of debris, burr comb, and areas that are difficult for bees to access. Regular cleaning of bottom boards removes the wax crumbs and debris where young larvae first begin feeding.

Replace old comb regularly 🔗

Replacing old combs every three to five years reduces the buildup of attractive dark wax, which moths strongly prefer. Comb rotation – replacing 20-25% of brood comb each year – is a practical way to keep comb fresh and less appealing to the pest.

Managing stored comb and equipment 🔗

Some of the worst wax moth damage happens not in active hives, but in stored supers containing drawn comb. Protecting this equipment requires deliberate effort.

Physical controls: light, ventilation, and freezing 🔗

Wax moths avoid well-lit, well-ventilated spaces. Storing empty hive boxes and combs in covered but open-walled sheds, stacking supers at right angles to increase airflow and light penetration, provides effective protection without chemicals. For smaller-scale beekeepers, freezing is equally reliable – placing infested or at-risk comb in a freezer for at least 72 hours kills all life stages of the wax moth. The University of Florida’s IFAS Extension recommends a minimum of 4.5 hours at -7°C, 3 hours at -12°C, or 2 hours at -15°C for extracted comb.

Chemical fumigation for stored equipment 🔗

For large-scale storage, chemical fumigants have traditionally been used. Fumigants such as aluminum phosphide, methyl bromide, phosphine gas, and magnesium phosphide are used for wax moth control in stored drawn comb, but these are regulated substances requiring special training and, in many regions, a restricted-use pesticide license. There is also a risk that chemical residues may be absorbed into beeswax and subsequently contaminate honey. Beekeepers should only purchase fumigants from dedicated beekeeping suppliers, and should only use products explicitly labeled for this purpose – under no circumstances should unregistered chemicals be used.

Naphthalene (mothballs) and paradichlorobenzene (PDB) – sometimes mentioned in older beekeeping literature – should not be used, as naphthalene is highly toxic to bees and accumulates in wax, and PDB is no longer acceptable due to health concerns.

Biological control with Bacillus thuringiensis 🔗

The most promising and bee-safe option for stored comb protection is the use of Bacillus thuringiensis (Bt) – a naturally occurring soil bacterium that produces proteins toxic to certain insect larvae. The Bt subspecies aizawai controls wax moth infestations by producing a crystallized protein that is specifically toxic to wax moth larvae, while being harmless to bees and humans.

Commercial products such as B402 (also known as Certan) are formulated from Bt subsp. aizawai. B402 leaves no residue in wax or honey, does not affect the taste of honey, and is suitable for organic farming. It is applied as a diluted spray (1 part B402 to 19 parts water) on both sides of frames before storage, and a single application provides protection through to the following season.

Recent research published in Nature Communications has demonstrated that combining a novel Bt strain with a lure-based entrapment device significantly reduces GWM larval populations in both laboratory and field conditions, pointing toward increasingly effective integrated approaches in the future. Importantly, only the aizawai subspecies of Bt should be used – some other strains of Bt are toxic to bees and humans, so beekeepers must not substitute other Bt products.

Integrated pest management (IPM) approach 🔗

No single method provides complete protection against the greater wax moth. Integrated Pest Management (IPM) is the most appropriate approach, since honeybees are highly vulnerable to insecticidal controls. A practical IPM strategy for wax moths combines several layers: keeping colonies strong and queenright; promptly removing weak colonies, dead-outs, and surplus comb; rotating and replacing old dark comb; storing equipment in well-ventilated, lit conditions; using physical controls like freezing; applying biological controls such as Bt on stored frames; and, where legally permitted and necessary, using approved chemical fumigants with full label compliance.

The bottom line is this: a thriving colony is its own best defense. Wax moths rarely overcome a healthy, well-managed hive. When infestations do take hold, they are almost always a symptom of deeper colony health issues – not just an isolated pest problem.

What do you think? If you’ve noticed wax moth damage in your hives or stored equipment, was colony strength a contributing factor – or did you find the infestation in otherwise healthy equipment? And with biological controls like Bt showing promising results, do you think they could eventually replace chemical fumigants in mainstream beekeeping practice?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC5492075/
2. https://www.lsuagcenter.com/profiles/madeleinestout/articles/page1706044465643
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC9814581/
4. http://bkbees.com/galleria-mellonella-an-in-depth-introduction-to-the-greater-wax-moth/
5. https://www.nature.com/articles/s41467-023-42946-4
6. https://edis.ifas.ufl.edu/publication/AA141
7. http://www.dave-cushman.net/bee/waxmothtreatment.html
8. https://www.epa.gov/pesticides/first-beehive-uses-currently-registered-active-ingredient-bacillus-thuringiensis-subsp
9. https://www.vita-europe.com/beehealth/product/b402/
10. https://www.clemson.edu/extension/beekeepers/fact-sheets-publications/wax-moth-ipm-publication.html
11. https://www.arbico-organics.com/category/WaxMoths-Galleria-mellonella-Achroia-grisella