Lesser Wax Moth (Achroia grisella)

The lesser wax moth (Achroia grisella) is the smaller relative of the greater wax moth; its larvae dig fine silk tunnels in the comb, in the debris on the hive floor and in stored frames. Strong colonies keep it in check easily; problems mostly arise in weak colonies and in poorly stored combs. Despite the similar-sounding name, it has nothing to do with the notifiable small hive beetle.

What is it and how does it spread?

The lesser wax moth is a moth species. At night the female enters through cracks in the hive or gaps in the store and lays her eggs along the edges of combs and among debris. The larvae feed on wax, pollen, cocoon remains and floor debris; they develop better in brood combs and old dark combs. It multiplies rapidly in the warm season and its development slows in the cold.

It is usually found in the same places as the greater wax moth (Galleria mellonella). Its damage progresses more slowly; but when both species are present together, stored comb can become unusable in a short time.

How to recognise it

Adult

It is a slender, silvery grey-brown moth about 1 cm long, with a distinctly yellowish head. The greater wax moth is noticeably larger and has more mottled wings.

Larva and cocoon

The larva is slender, whitish-grey with a brown head and grows to at most about 1.5 cm. The larva of the greater wax moth is thicker and noticeably longer. When mature, the larvae spin white silk cocoons covered on the outside with debris in the corners and cracks of the hive.

Signs in the hive and in storage

• Bald brood: As the larva advances beneath the cappings, cells with their cappings removed and live white pupae visible inside line up in a straight or winding row.
• Silk trails: Fine silk tunnels close to the surface on the comb face and on cell bases.
• On the floorboard: Heaps of debris bound together with silk, and winding silk paths.
• In stored frames: Webbing, black faecal pellets, cocoons in the corners of frames and hives.

How it differs from similar conditions

What to do

1. Strengthen the colony: Remove surplus frames that the bees cannot cover, and unite weak colonies.
2. Clean out the tunnels: Remove capping debris along the row of bald brood and take out the larvae; replace heavily infested frames.
3. Clean the floorboard: Heaps of debris are both food and a hiding place for the larvae.
4. Seal cracks, and scrape away cocoons in the corners of the hive.

Protecting stored combs

• Freezing: Keeping frames in a deep freezer (about –18 °C) for at least 24–48 hours kills eggs, larvae and pupae. Then store them in closed boxes that the moth cannot enter.
• Cool, light and airy storage: The moth likes dark, warm and enclosed conditions. Store frames spaced apart.
• Comb selection: Do not keep dark brood combs in storage for long; render down old ones.
• Biological product: Authorised products containing Bacillus thuringiensis can be used against larvae in stored comb; follow the package leaflet.

Naming confusion

In the past this topic was mistakenly confused with the small hive beetle in some sources. The correct picture is:

• Lesser wax moth, Achroia grisella (Turkish: küçük mum güvesi): a moth; a common hive pest that is not notifiable.
• Small hive beetle, Aethina tumida (Turkish: küçük kovan böceği): a beetle; notifiable and a far more serious threat.