A couple of weeks ago, I’m dismayed to find around fifty or more dead and dying bees out front of a small colony. They have overwintered well in a 14 x 12″ multi-story poly nuc with plenty honey and pollen stores. This happens on several days with several hundred deaths in total. A few of the bees are crawling up grass stems (CBPV Type-1) but most are dying or dead and many are small, hairless, black and shiny with shortened abdomens which ties in with CBPV Type-2.
Poisoning?
Last summer, several hundred bees from this colony came tumbling out of their hive and lay spinning on their backs before dying. I thought that they may have been poisoned because potatoes are sprayed at this time. I collected a sample of bees which was analysed at the Scottish Government (SASA) labs in Edinburgh under the Wildlife Incident Investigation Scheme. No pesticide residues were found.
Strong honey producers
This colony (along with their other half from swarm control measures) produced an amazing 82lbs honey last summer, plus a full super for winter stores. So, it was strong and appeared healthy until the mystery episode. I transferred them into a nuc for winter since they had taken a beating with possible disease and reduced numbers. They were at risk of robbing also.
Healthy foragers
Low varroa levels
Oxalic acid 2g was sublimated in December, and a recent test dose caused a total of 60 varroa to fall over a week. No deformed wing virus (DWV) has been seen.
CBPV
According to my Honeybee Veterinary Medicine:Apis mellifera L.Honeybee Veterinary medicine by Nicholas Vidal-Naquet, this contagious disease often presents in strong colonies and can persist in colonies throughout the year. Often thousands of dead bees are found outside the hive. Not all colonies will be affected in an apiary which is a relief. I try to keep colonies as far apart as possible for this reason. The two types often appear simultaneously as I think they have here in my colony.
Management
Well, there is no treatment for viruses but limiting overcrowding might be useful. To this end, I plan to move my bees back onto standard brood frames and boxes and limit the size of colonies. To get rid of the virus load in comb, I performed a shook swarm and got the bees onto clean comb. The death rate appears to have fallen. I’m seeing only several dead bees daily out front. Fingers crossed!
Awful. But not disastrous, I’m glad to see. Taking careful note of how you’ve dealt with it at the practical level
Since I am not a bee keeper but very much interested in them, please tell me what this means:-
I performed a shook swarm.
That’s terrible dying in such numbers. Poor things.
It is a beekeeping term which means that a situation, like when bees swarm naturally, is created. In a swarm the bees that leave the hive take a load of honey with them and move to a new home where they build new comb. In this situation, all the bees are shaken off the brood frames, by the beekeeper, onto new frames. In this case I did it to get the bees off the frames which were likely to have contained heavy virus loads. It sounds like a harsh procedure but the bees are resilient, and in the long run it does more good than harm. Already the numbers of bees dead outside the hive have reduced markedly. I wouldn’t do this to a colony that was weak and very sick but this one is strong. The numbers of dead bees may seem high but it can be many more than that, and in CBPV Type 1 it seems that the virus is more virulent with higher mortality rates.