Lesser Wax Moth
Achroia grisella (Fabricius)
📖 Description
Lesser Wax Moth (Achroia grisella) is a serious secondary pest of managed honey bee colonies and stored beeswax comb across the Indian subcontinent and worldwide. Often co-occurs with Greater Wax Moth but is generally less damaging. Particularly severe in apiaries of Apis cerana indica (Indian hive bee — native) and Apis mellifera (European honey bee — widely used in commercial Indian apiaries). India has over 12 lakh bee colonies producing over 95,000 tonnes of honey annually. The pest is unusual among apicultural pests because (a) it prefers old dark comb with high pollen content — different from Greater Wax Moth which prefers new wax, (b) adult males produce ultrasonic courtship songs that attract females — making acoustic monitoring possible, (c) larvae are smaller and more secretive than Greater Wax Moth larvae, often hiding in debris at the bottom board, (d) a single female lays 200-400 eggs in crevices of hive wood or comb, with larvae developing over 5-7 weeks, (e) the pest is most damaging to weak or queenless colonies and stored comb, and (f) populations build up rapidly in the warm humid months of monsoon and post-monsoon. IPM with strong colony maintenance, regular hive inspection, prompt removal and freezing of infested comb, Bt and acetic acid treatments for stored comb, PDB fumigation for long-term comb storage, regular replacement of old dark comb, screened bottom boards, full-sun apiary placement, and good apiary hygiene provides effective control. The pest is a particular concern for Indian beekeepers because (i) India is a major honey-producing nation with rapidly growing commercial apiculture, (ii) traditional log and clay hives provide numerous crevices for moth egg-laying, (iii) India’s warm humid climate favours wax moth development year-round in many regions, (iv) many Indian beekeepers use old dark comb for multiple seasons (which favours Lesser Wax Moth), and (v) the pest is often overlooked because its damage is less conspicuous than Greater Wax Moth damage.
⚠️ Symptoms to watch for
- Small silken tunnels in old dark comb and pollen cells, webbing and frass in pollen storage cells, damage to old brood comb (less severe than Greater Wax Moth), larvae often hide in debris at the bottom board, contaminated pollen and honey, weakened bee colonies in neglected apiaries, absconding of weak colonies. Economic loss typically 10-30% of comb in neglected apiaries — less than Greater Wax Moth but often co-occurring.
🩹 Treatment
- Same as Greater Wax Moth: inspect hives every 7-10 days, freeze infested comb at -7°C for 4.5 hours, keep colonies strong and populous, store drawn comb only after PDB/acetic acid fumigation, do not leave drawn comb unattended in unused supers.
🌿 Organic treatments
- Maintain strong populous colonies (most effective biological control), apply Bt var. aizawai spray on stored comb, apply Beauveria bassiana to stored comb, fumigate stored comb with glacial acetic acid, use essential oil blends (peppermint, lemongrass) on stored comb to repel adults, expose stored comb to bright sunlight in sealed bags, use upper ventilation to prevent humidity, keep hives in full sun, use screened bottom boards with vegetable oil tray, replace old dark comb (which is most attractive to Lesser Wax Moth) with new foundation regularly.
🧪 Chemical treatments
- PDB (para-dichlorobenzene) crystals @ 6-8 crystals per shallow super for stored comb fumigation, aluminium phosphide (Phostoxin) tablets @ 1 tablet per 5 stacked supers in sealed stacks (use only by trained operators), sulphur fumigation @ 50 g sulphur per cubic metre of stacked comb. NEVER apply chemical insecticides inside active bee colonies.
🛡️ Prevention
- Maintain strong populous bee colonies, regularly replace old dark comb (which is most attractive to Lesser Wax Moth) with new foundation, store drawn comb in sealed stacks with PDB crystals or after Bt/acetic acid treatment, inspect hives every 7-10 days, keep hives in full sun, use screened bottom boards with oil tray, reduce entrance size during dearth periods, avoid small splits too weak to defend comb, store harvested supers promptly after extraction, practice good apiary hygiene, manage Indian hive beetle and small hive beetle, use queen excluders to keep brood nest compact.
🪴 Affected plants
- Honey bee colonies (Apis cerana indica, Apis mellifera, Apis florea, Apis dorsata); damages old dark comb, bee bread, pollen, and stored wax; particularly attracted to old comb with high pollen content. Not a plant pest — an apicultural pest.
🦋 Natural predators
- Worker bees (most important — kill and remove eggs and larvae in strong colonies), ants, pirate bugs (Orius spp.), spiders, earwigs, silverfish. No commercial biological control agents are widely used.
🌱 Host plants
- Honey bee colonies (Apis cerana, Apis mellifera, Apis florea, Apis dorsata) and stored beeswax comb. Not a plant pest.
🔄 Lifecycle
- Adult female lays 200-400 eggs in crevices of hive wood or comb.
- Egg incubation 5-7 days.
- Larva passes through 7-9 instars over 35-50 days; larvae tunnel through old comb and pollen cells.
- Mature larva pupates in a silken cocoon attached to hive wood.
- Pupal stage 10-14 days.
- Adult lifespan 7-12 days (does not feed).
- Total life cycle 6-10 weeks at 25-30°C; 4-5 overlapping generations per year in tropical India.
📅 Season
- Year-round in tropical India; peaks Jun-Nov (warm humid monsoon conditions most favourable for moth reproduction, and bee colonies may be weakened by dearth)
🔎 Appearance
- Adult is a small, slender, silvery-grey moth; forewings silver-grey with darker grey outer margin, hindwings pointed with long fringes.
- At rest, wings are folded flat over body giving a slender appearance.
- Larvae are creamy-white caterpillars with brown head capsule, smaller than Greater Wax Moth larvae.
- Pupae are light brown in silken cocoons.
- Distinct from Greater Wax Moth by smaller size, slender build, silvery colour, and preference for old dark comb rather than new wax.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- Southeast Asia
- Cosmopolitan in Tropical
- Subtropical
- and Temperate Regions Worldwide
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