Cleaning, freezing and storing supers so wax moth cannot get in

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Why this is worth doing properly

Bees use a lot of honey to make a little wax. A box of drawn super comb is worth more to you next spring than the honey that came out of it. A colony given drawn comb can fill it straight away instead of spending weeks and a lot of stores building it.

This starts the moment the supers come off, so have somewhere ready before harvest day.

Wax moth is what takes it away. It is only a minor pest of a strong colony, but it is a serious pest of stored comb. 1 A stack of supers in a warm shed with no bees in it is the best home a wax moth will ever find.

The order that works

Four steps, and the order matters more than any single step:

1. Let the bees clean them.
2. Let them dry fully.
3. Freeze for 48 hours, sealed.
4. Keep them sealed, or store them cold and airy.

The freezer does the killing, not the bag. Sealing comb in plastic does not kill anything. If there are wax moth eggs already in the wax, and in September there usually are, all a sealed bag does is give them a private room. Bag the frames, freeze them in the bag, then keep them sealed.

1. Let the bees clean them

After extracting, the comb is wet with the honey the extractor could not throw out. The extractor and the tanks want putting away properly in the same week. Bees will take every bit of that back if you let them, which leaves the comb dry and much less attractive to wax moth and mould. If the moth got in anyway, or got in last year, saving what you can is a separate job.

Put the wet supers back on the hives they came off, above the crown board, and leave them for a few days. Above the crown board rather than under it, so the bees treat it as robbing out a store rather than as part of the hive.

Do it in the late evening and make sure the stack is bee-tight. This is the single easiest way to start a robbing war in an apiary, and wet supers left out in the open will do it in minutes.

Do not put wet supers out in the open air “for the bees to have”. It sets every colony in the area fighting, and it spreads disease between them. Wasps at the hive covers the precautions if you have to do this in the open.

2. Dry them

Once the bees have finished, the comb still holds moisture. Stack the supers somewhere airy for a few days before you do anything else.

This is the step people skip, and it is why they open a sealed box in March and find mould. Cold plus sealed plus damp equals mould, every time. Comb that has gone mouldy is not always ruined, but the bees will have to clean it before they will use it, which puts you back where you started.

3. Freeze for 48 hours

The NBU calls freezing the safest and easiest treatment, and says a domestic freezer kills every life stage of wax moth, eggs included. 1 Its wax moth sheet gives 24 hours for frames. Its leaflet on pests of adult bees gives 48. We say 48 as the working minimum, because it covers both figures, and because frames in the middle of a stacked freezer take a while to reach temperature. Longer costs nothing. A weekend, or a week, is fine.

Neither document gives a temperature, which is the gap worth knowing about. It means a proper four star freezer compartment, not the icebox in the top of a fridge.

• Scrape off any cocoons you can see on the boxes and frames first.
• Put the frames in tightly closed bags, zip-tied or taped shut, before they go in.
• Take them out and leave them in the unopened bag until you need them, or move them into a sealed container.

Leaving them sealed on the way out matters for a second reason: frozen comb brought into a warm room will sweat. Let it come back up to room temperature inside the bag, then it is dry when you open it.

A chest freezer takes a super at a time. A kitchen freezer takes a few frames. Either is fine, it just changes how many rounds you do.

4. Or store them cold and airy instead

Sealing is not the only answer. Cold slows wax moth right down, which is why it is a worse problem in hot countries than here. 1 If you have somewhere cold and unheated, an open stack works and needs no freezer:

• Put a queen excluder on a hive stand, so nothing can walk in from below.
• Stack the boxes on it, each with three or four frames fewer than it would normally hold, so air moves between the combs.
• Another queen excluder and a roof on the top.

The excluders keep mice out while letting air through. The gaps between frames are the working part: a stack of tightly packed comb is still a wax moth nursery even in the cold.

Check it during a mild winter. Look for silk trails and tunnelling, and freeze anything you find.

Do not store old dark brood comb or frames of pollen this way. Wax moth goes for dark comb and old cocoons first. Brood comb wants freezing and sealing, or melting down.

The other option, and why we do not use it

Acetic acid fumigation kills every life stage too, and it also disinfects comb after Nosema apis. The NBU says it may not work on Nosema ceranae. 2 It is a strong acid, it needs careful handling and proper ventilation, and it corrodes metal parts. For a few supers a domestic freezer is easier and safer. For a large stack in a shed with no freezer, it is worth reading up on.

Flow frames are washed, not extracted

Flow frames do not go in an extractor and they do not go back on for the bees to lick out in the same way, so the routine is different. Flow’s own instructions: 3

• Set the cells to the open position and take the bottom plug out.
• Wash in warm to hot water, with the frame slanted towards the plug end so water, honey and wax all run out.
• Dry thoroughly.
• Seal in plastic, then freeze overnight to kill any eggs or larvae in the wax.
• Store somewhere cool, dry and dark, because the frame plastic is UV sensitive.

Note that Flow seal before freezing too, the same order as the NBU: the plastic stops anything getting back in after the freezer has done its work.

Wear a mask for the clean-up

If you are scraping out a box that has already been infested, do it outside. Moth wing scales and the silk and frass the larvae leave behind can irritate your airways, and the NBU recommends respiratory protection if you have any sensitivity. 1 It also smells revolting.

What to throw away

Comb that has been tunnelled through is not worth saving. Scrape the frames back to the wood, scrub the boxes out, and start again with foundation. 1 Old dark brood comb should be going anyway on a two or three year rotation. 2 That habit does more for disease control than almost anything else.

The frames themselves are usually fine once scraped. Look for the boat-shaped grooves wax moth chews into the wood near the lugs, and bin anything badly gnawed.

Cleaning the boxes themselves, and the freezing time for dismantled woodwork, are in Hive tools, and keeping them clean.

Bags, ties and freezer space are on the autumn kit list, which is worth reading in July rather than the day the supers come off.

The short version

• Bees clean, then dry, then freeze 48 hours sealed, then keep sealed.
• Sealing on its own protects the moth. The freezer does the killing.
• Damp plus sealed equals mould. Dry it first.
• Or store cold and airy on excluders, with gaps between the frames.
• Never store dark brood comb or pollen frames in an open stack.
• Wax moth working through comb in a live colony is a sign to ask why that colony is weak.