Wax Moths

Posted by Jon on Jun 30, 2010 in Beekeeping, Hive problems | 0 comments

I opened one of our hives earlier this year to find that the colony had disappeared leaving behind discoloured comb which I put to one side to do something with once I had had a chance to look at it more closely. This was a few months ago now, and it has been on my mind recently to destroy the frames so yesterday, I went to have a look. Thankfully, I had sealed it and put it in a barn away from all my other equipment and hives fearing the possibility of disease, a sensible move as when I opened the brood box up it became apparent that I had a major wax moth infestation.

The greater wax moth (Galleria mellonella) is 1.3 – 1.9cm long whereas the lesser wax moth (Achroia grisella) is smaller but the damage to the hive is very similar. From the size of the moths we had and its pupae distribution, it was the greater wax moth thriving in our abandoned hive.

(click photos to see larger slideshow)

The moth isn’t a worry in healthy hives as the bees will keep the numbers down, but if the hive is compromised then it can be catastrophic and hence its involvement in Colony Collapse Disorder (CDD). Obviously, our hive was empty so the moths had free run as you can see from the photos. The lifecycle of the moth is in 4 stages, eggs, larvae, pupae and adult. The adult doesn’t feed and is merely an egg fertilising and laying stage, it is the larvae growing from an egg laid in a cell in the comb that burrows through the wax, eating pollen stores, honey, hive detritus and even the bee brood in some cases. The larvae nibble away the woodframe to create depressions where they pupate. The greater wax moth pupates in groups whereas the lesser one tends to pupate individually (another pointer that we had the greater variety).

We didn’t see the complete destruction that is shown in some of the textbooks (like David Cramp’s). Whether this was because the comb was diseased, they didn’t like the crystallised honey (this was oil seed rape and was perhaps a reason why the hive was abandoned) or we had caught the infestation early enough, I have no idea. Whichever, it seemed sensible to destroy the frames away from our other hives.

Having said this, in Natural Beekeeping, Ross Conrad says

The wax moth is an opportunist, a scavenger to whom nature has delegated the task of cleaning up dead hives, thereby acting as a natural form of disease prevention to help keep other colonies in the neighbourhood healthy.

There are ways to protect your stored comb against wax moth, including freezing or spraying them with Bacillus thuringiensis or leaving them in the lightand fresh air (moths don’t like light or ventilation). I’ve now destroyed the comb and thoroughly cleaned the hive and will be more careful about leaving comb in a hive for so long in the future.