Wax Moth: Killer in the Night

On Saturday July 16th we finally turned off our cameras and declared our bumblebee nest inactive. We'd seen no bee action in or around it for 3 full days, apart from one large bee leaving, that looked large enough to possibly be a queen. A sad moment, given all the time and energy invested into our Bumblebees, but certainly not the end of our journey - still much to do. 

I will consign a fuller write up of the our findings from our examination of the box to a later blog post, but for now just a few words on Wax Moth.

Wax Moth is a Bumblebee parasite, a fact we were not aware of until the last few weeks of the function of our nest. It seems that honey beekeepers are well aware of the existence and precautions required against the wax moth; knowledge that perhaps doesn't extend readily down to the novice Bumblebee hobbyist; indeed, all the information I've found online is directed towards honeybee keepers. 

The bottom line is this: the wax moth spends time checking out the nest and even staying close to pick up the scent from the nest. Then it enters the nest secretively with the aim of laying its eggs without being discovered. The moth larvae build these incredible "silky" channels and tunnels to move around  the nest in. It's like a whole underground network made of really tough and sticky silky fibrous material. This protects them from being attacked by the bees. Then they basically munch their way through the wax pots made by the bees until the colony can no longer survive. 

According to experts at the Bumblebee Conservation Trust, it is thought that up to 80% of garden-sited bumblee nests succumb to the wax moth. Some of the reasons stated for this being so high include the general garden habitat, which appeals to the moth and also that garden bumble bee nests are generally much more conspicuous (compared to say, a small hole in a mossy bank on the edge of field). I'm not 100% convinced the latter is a good explanation, or at least interpretation (it suggests that the moths are able to discern which man-made constructions comprise bumblebee nests); my personal feeling is that Bumblebees and their nests are more conspicuous in a garden simply by nature of the confined space and land area that is occupied. Add to this the other man-made features which may attract the moths, such as lighting,  and what you find is bees and moths habiting (say) the same 100m-square area: basically, dinner on a plate for the moth.

We may have unwittingly contributed to this situation ourselves by having solar lighting in the garden and infra-red lighting on our CCTV cameras. Once in a while we saw a moth at the mouth of the nestbox and wondered whether the infra-red had attracted it there. The jury is still out for me on that one - because what we didn't see was sustained activity around the camera, which I would have expected if the theory was true. 

However, there is another side to the story. When we opened up the Koppert Hive (which proved extremely difficult to do) we discovered that the wax moth larvae in the upper section of the box all eminated from around where our internal camera was sited (poking through the box lid). This left us wondering whether the heat/infrared from the camera had provided an attraction to the moth/larvae and a preferred environment for it to develop. At this stage I need to do more research/reading to be able to answer. 

 wax moth larvae and cocoons extending down the box side near the infrared camera

In a sense then, I was paradoxically relieved to discover that there had also been significant larvae development at the base of the box, underneath the whole nest. Perhaps, again, this leads to a theory of warmth being desirable, but it does suggest that it was not the camera and camera alone that provided an environment for the moth development. 

 Wax moth larvae in the base of the box, embedded in the polystyrene

Their invasion on the nest is really rather horrible. The larvae are bright yellow/green, up to 2cm long and fast movers. (There are lots of pictures on the web, so I didn't take any close ups to publish here). They hide out in their silk cocoons, which are dense and sticky (and why the box lid was so hard to remove; we almost had to rip it off). They seemed to have built a vast structure of cocoon tunnels to hide in around the edges of the box, away from the core of the nest itself, but these then extend into the nest/wax pot area in a web of silk paths and make the whole structure one very sticky and matted mess of silk, wax, honey and pollen. It seems to me it's possible this is responsible for restricting the movement and hatching of bees within the body of the nest structure, which aside from the destroying the wax itself, may also contribute to the nest decline. 

I was very sad to discover our box had been invaded by wax moth - we suspected it around mid June after a decline in audio activity from the nest, before a slight reduction in visible activity. By the beginning of July I was 99% certain - at one point we did see a moth inside the box on the CCTV, although we didn't see the larvae. Then the rapid decline began over the first 10 days of July, and I was sure. I was more sure than a sure thing from Sure Street, Sureland when on the final day I could see the larvae actually moving around on the nest bedding on the CCTV. Pretty gross actually. I'd like to try and go back over the CCTV if I have time to try and figure out when the initial invasion happened. 

I was gutted that we were powerless to help - or at least seemed so at the time, the Koppert box being a sealed unit. But in fact, having now disassembled it, that is not the case, (it's just cleverly constructed and clipped together) and it may have been possible to intervene earlier if we had really been sure of what was going.

This was partly down to lack of visibility inside the box and partly down to not really knowing about the risks of the wax moth until late in the day. The other lesson I will learn from this, is that it would have paid to have checked the nestbox all round from time to time. We believed the best thing was to leave it as alone as possible in its shelter and avoid stressing the bees by moving, examining and even opening it . But in hindsight, this might actually have paid off if we'd seen evidence of intrusion round the back of the box where the camera was. Although, to be fair, once the damage had got to the stage where it was visible, it may have been too late.

For next year we will try some strategies to try and reduce the risk of wax moth invasion:

• Seal all the ventilation holes around the nest box by sticking on small webbing (as used on our wooden box to prevent Ant intrusion)
• Eliminate lighting (or at least any nearby) in the garden
• Control the opening of the nest box using a wireless timer (also available from Koppert)
• reduce usage of the infrared camera, certainly inside the box
• use "Certan" treatment around the box
• plant some mint, which may help to discourage them

I would actually like to some research at this stage with what's left over from our box. We could use the wax pots that are left over (substantial quantity) to both track the rate at which the larvae can destroy it, but also potentially assess the effects of the above strategies - for example, whether the infrared attracts the moth and encourages development. The only thing is, we don't really want to end up creating a whole colony of new moths which could go on to destroy other bumble nests or come back next year to destroy ours. So, for the timebeing, we are still contemplating this.

But one thing is clear for next year: whatever we do, we have to try and prevent this devastating killer getting near our nest.