Lesson 65: Wax Moths and Storing Comb

The pest of empty comb, and how to store your drawn comb safely

Drawn comb is one of a beekeeper's most valuable assets. Bees use a lot of honey to build it (lesson 10), and reusing it gives colonies a head start. Its biggest enemy is the wax moth. Wax moths rarely hurt a strong colony, but they can destroy stored comb in a couple of weeks in warm weather.

Know the wax moth

Two species attack comb: - the greater wax moth (Galleria mellonella), the more destructive; - the lesser wax moth (Achroia grisella).

The adults are plain grayish-brown moths that lay eggs in cracks in hives and stored equipment. The damage is done by the larvae ("wax worms"): - whitish-gray caterpillars, up to about 1 inch long when grown, soft, with fleshy legs along the body; - they tunnel through comb, eating pollen, cocoons left in brood cells, and wax; - they spin silk webbing as they go and leave dark droppings (frass); - they chew grooves into wooden frames and boxes to spin their cocoons.

A badly infested comb becomes a mass of webbing and debris the bees can't use.

How it looks: Wax moth damage: tunnels, webbing and ruined comb.

Silk webbing and cocoons left by wax moth larvae.

Don't confuse them with small hive beetle larvae (lesson 64): beetle larvae are smaller (about ½ inch), tougher, spiny, with legs only at the front, and don't spin webs.

Wax moths in living colonies

Strong colonies keep wax moths out. Bees remove eggs and larvae. If you find wax moths in a live colony, something else went wrong first, usually queen loss or another problem that weakened the colony (lessons 43–44).

• Keep colonies strong and queenright.
• Don't give them more comb than they can cover: don't over-super.
• Move a weak colony into smaller equipment (a nuc box) so it can guard its combs.
• A mild infestation in a frame or box: put it on a strong colony and the bees will clean it up. A severe one: scrape the comb off and let bees rebuild.

Storing comb safely

Wax moths are active whenever it's warm. They're no threat when temperatures stay below about 40°F. How you store comb depends on the season and your climate:

1. Freeze first. Freezing kills wax moth eggs and larvae. Freeze frames or supers for at least 72 hours (some beekeepers keep them frozen until needed). Then store them so moths can't get back in (sealed stacks or bags).

2. Light and air. Wax moths prefer dark, still spaces. Some beekeepers store supers in stacks that let light and air through, crisscrossed or in open racks. Wax moth larvae prefer dark, old brood comb (it holds pollen and larval skins), so honey-super comb is at lower risk.

3. Cold storage. In cold climates, comb can be stored in an unheated building through the winter.

4. Moth crystals (fumigant). Some beekeepers use paradichlorobenzene (PDB) crystals sold for wax moth control: - Only products labeled for use on beeswax comb, used exactly by the label. - Stack supers, tape the cracks, put the crystals on paper on top of the frames (every few boxes), and cover the stack; refill as they evaporate. - Air the combs out well before putting them back on hives. - Never use mothballs made of naphthalene. Naphthalene contaminates the wax and kills bees. - Never store honey supers you plan to harvest with crystals. The fumes can be absorbed.

5. Other options some beekeepers use: acetic acid (glacial, 80%) fumigation, and a Bacillus thuringiensis (Bt) product that kills moth larvae. Use only products registered for this use, and follow the label.

Store only sound comb. Before storing, check for small hive beetles; beetle larvae in stored supers can slime the honey (lesson 64).

What to remember

• Wax moth larvae destroy comb with tunnels, webbing and droppings; they're a sign of a weak colony or poorly stored comb.
• Strong colonies protect their own comb; don't give them more than they can cover.
• Store comb safely: freeze 72+ hours, then keep it sealed, cold, or in light and air. PDB per label, never naphthalene.
• Moths are inactive below about 40°F.

Quick check

1. You find wax moth larvae in a live colony. What does that usually tell you?
2. How long should you freeze comb to kill wax moths?
3. Why must you never use ordinary naphthalene mothballs on stored comb?

Show answers

1. The colony was weakened by something else first, often queen loss, and couldn't guard its combs. 2. At least 72 hours. 3. Naphthalene contaminates the wax and kills bees.

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Adapted from: University of Arkansas, Complete Beekeeping Short Course, Part 13 (Zawislak); Penn State Extension, A Quick Reference Guide to Honey Bee Parasites, Pests, Predators, and Diseases; Delaplane, Honey Bees and Beekeeping (UGA Bulletin 1045, rev. 2017); Purdue Extension, Advanced Beekeeping (4-H-1059); UF/IFAS Extension, Welcome to the Apiary! (4H446, 2024).

Photos: Wax moth damage and webbing, Goldmull, CC BY 3.0 (via Wikimedia Commons).

Adapted from university Extension sources. Experienced Georgia beekeepers are reviewing these lessons. See something that doesn't match your experience? Tell us.