I often hear beekeepers say that it’s not too late to lose your bees even in March, usually with a reference to feeding. I was asked by some friends (and former students of mine) to do a PM on their hive as the colony – having been active earlier a few weeks previously – had died. This colony had swarmed the previous year and also produced a super of honey on top of that which they were left with as stores, and had a good population bees going in to the winter as far as we know, so they were understandably concerned and sad that this had happened, and whether it could have been prevented.
There were very few bees on the floor of the hive when I looked today, and plenty of stores of pollen and honey in the super and either side of the nest. There was a small patch of capped and slightly chewed brood, but no eggs or young larvae. A number of the bees were deformed, and there was evidence of mites on a few of them. I found the queen who looked a nice specimen, but the cluster must have been tiny and therefore it lost its ability to function correctly. I think it’s difficult when we’ve had a large and productive colony who, if they swarm, leave behind a well-resourced hive so it is difficult to judge when the problems start. They were flying a few weeks ago, although one is never certain (especially if they aren’t carrying pollen) whether the bees entering and leaving the hive are robbers or foragers. Bees can go on a surprisingly long time, but we did have a very cold snap a week or so ago, and maybe that was enough to cause them to succumb. It could be that if lots of the bees were subnormal they could not support the colony, and this became a point of no return.
The bees who swarmed from this colony are in a top bar next to this one with the original queen potentially – probably – still happily doing her thing in that hive; it’s certainly very active and productive. Her daughter may not have been well-mated, or perhaps had less rigour against the mites. The post mortem of this colony seemed to be virtually identical to the others I have seen – except these had a lot more honey – but essentially exactly the same pattern. They were in a poly hive so insulation wouldn’t have been a problem. We talk a lot about whether bees are hygienic towards mites, which of course deals with the physical battle against them attaching to the bees’ bodies, but there will be other physiological characteristics, such as a susceptibility to the viral load carried as the mites feed which will affect the likely outcome. I saw a number of deformed bees with short abdomens, and a handful with deformed wing virus.
I have cleaned the hive and removed the combs from the frames as they had started to go mouldy. This happens after the bees have died, or because they are too small to maintain the correct temperature and humidity within the hive – which is why you sometimes get them on the edge frames of a small colony that has overwintered in a brood box. Here are some photos:
The bees had not been treated for Varroa, but as I have said many times before, treating creates bees that need treating, rather than a solution to the mite problem. The two other hives on the site – so the swarm from this colony, and another swarm who seems to be establishing itself now after a gradual start – have not been treated and yet are coping with any mites, so it is better to prioritise colonies who can survive and thrive without treatment in the long term.