Dealing with Wax moth.
Wax moths come in two different flavours; the Lesser Wax Moth Achroia grisella and the Greater wax moth, Galleria mellonella. It’s the greater moth that will tunnel (make galleries – hence the Latin name) into the wood or into polystyrene hives. The moth prefer brood comb to honey only (super) combs and they prefer dry comb to wet, although we cannot be sure that a wet super comb will never have wax moth larvae in them. They will burrow through polystyrene which must have no nutritional value to them, so nothing is safe! By wet I mean extracted combs that have not had the residue honey removed by the bees.
The moths tend to be apparent in late summer so it’s the time when we are dealing with extracted supers when we have to be on the look-out to stop them getting into the comb; although this is not the only time they are likely to cause a problem as stored combs can look OK in September and be ruined by Spring.
At extracting time, I put the ‘wet’ supers back on the hives (or wets as some call them) over a crown-board with one porter bee escape removed. The bees should consider the supers ‘outside’ the hive and remove the remaining honey from them. This needs to be done in the evening as the bees will think there’s honey close-by and outside the hive and go searching for it. Because the round dance – used for short distances from the nest - doesn’t give range or direction, the bees can start to look about and rob another hive. They don’t do this at night and by morning the risk is much reduced. After a week or so the wet supers will be dry and can be removed and stored.
Storage is best done by stacking up the supers or empty boxes on something like a sheet of plywood with a couple of sheets of newspapers in between each box. At the top of the stack some sort of mesh should be used over a crown board opening to stop bugs getting in. (I use a heavy greenhouse shading material, then a queen excluder on top which allows ventilation but no insects or mice to get in).
Ideally you won’t have any moths inside – it’s worth checking a few weeks later as one small moth can fly in in seconds. A strong hive with a reduced entrance will tend to keep the moths out although it is still possible that a moth or two will get in whilst supers are on the hive. Wax moth larvae activity will reduce as the weather gets cooler. However if you allow them to remain over winter, as mentioned above, you could well have a nasty surprise in spring.
Removal of wax moth IF they get in to a working hive.
To identify wax moth larvae you often see lines or tunnels through the comb. If the moth is present in a hive – and more likely in brood comb, you may see a line of uncapped brood; The moth will be at one end of this. To remove the larva, shake most of the bees off the frame and then rap your hive tool against the frame for, say 10 seconds, you will invariably see a wriggle of the larva coming out of the comb or see it just under the capping – at which time it can be squashed or scooped out.
Wax moth larvae - after they have got in stored comb.
If numerous larvae have a free-reign on wax comb it can be a real mess with furry tunnels and cocoons all over the place. In which case the comb will need to be replaced. Some comb damage can be scraped out with your hive tool or a (blunt) wood chisel. The bees will repair the damage when they are ready, once the frame goes on the hive.
There are several ways of dealing with them.
1) Freezing. 24 hours in a deep freezer will kill the moth, larvae and pupae. Leaving a stack of supers out in sub zero temperatures over winter will also kill them; if you can guarantee cold weather of course.
2) Fumigating with Sulphur Strips. These are available from some of the main beekeeping suppliers and the fumes are nasty.
3) Fumigation with 80% Acetic (Ethanoic) Acid. Again this is nasty stuff and it can be difficult to get as many freight carriers won’t carry it. Fumigation with Ethanoic acid also destroys EFB and nosema spores so it can be beneficial as part of winter duties in any case.
4) Old methods of fumigation, PBD crystals for example, should NOT be used as being either illegal or dangerous to bees and comb or both.
Later I will give details of fumigation methods.