The bee research group in my country, bijen@wur, organized a symposium last month which I didn’t attend. One of the speakers there was bee researcher Dennis van Engelsdorp (weirdly dutch sounding last name, translates to “English village”). He presented statistical data from a beekeeper survey that suggested that annually replacing to much of the comb (50% or more) negatively influences colony health. Often the idea of replacing comb is to prevent buildup of pesticides and/or pathogens, but it also looks ugly blackish comb. But the data shows that beekeepers who replaced 50% or more of their comb compared to beekeepers who don’t replace any, lose more colonies over winter.
It is unclear what causes this, the survey was not comprehensive enough for any analysis like that but the data is clear. They suggest not to replace more than about 20% of your comb annually. I was aiming to replace about a third of the comb but according to this information I will have to amend that. Apparently reusing comb from old colonies is also not advised as it also caused more winter deaths. The only problem is the lack of additional information in the survey. For instance it is unclear what the origins where of the reused combs. Perhaps the old colony died of disease.
So much is unclear, it wasn’t a study but only a survey. What is clear is that you shouldn’t renew to much of your combs annually. See the accompanying video for yourself (there is also a link to the web page in its description):
Making sure my colonies survive the winter period is, after egg laying workers and a queen-less colony the most stressful thing I have had to deal with. A colony needs to be big enough to have a chance of surviving the winter. During the winter time the bees will congregate into a ball of bees inside the hive. The bees have to keep this ball at a relatively constant temperature of around 18-35ºC (35ºC being an indication that the colony has brood), averaging at about 24ºC, even if the temperature outside gets as low as -15 ºC outside the hive. The bees will only be able to maintain this temperature when there are enough bees. The bees vibrate their flight muscles to generate heat. During winter many, many bees will die, only hives that can sustain this die off will survive.
A beekeeper is supposed to asses his colonies strength in late summer to early fall and decide if he thinks this colony will survive the winter or not. If there is any doubt the beekeeper should combine colonies to create a stronger colony of which he can be sure it will survive winter. A colony should occupy at least 6 frames in a hive to have any chance of surviving the winter. If a colony doesn’t meet this requirement then the beekeeper should combine this colony with an other weaker colony. As I only have two colony I either combine them or I don’t.
The easy way to combine colonies is by placing a newspaper on top of an open hive box of the one colony and spraying the newspaper with sugar water. Then you place the brood box(es) of the second hive on top. The bees will have to eat through the newspaper to reach each other. The hypothesis is that by chewing through the newspaper they will all smell the same (newspaper ink) and hostility will be averted. You obviously will have to kill one of the two queens, do this a few days before uniting the hives and place the hive that still has it’s queen on top. Just parroting theory here…
As I was reasonably sure my original colony was big enough to survive winter I didn’t unite my two colonies, the colony that was the result of my artificial swarm was borderline big enough. But as I would end up with one colony either way, I chose the selfish option and I kept both colonies separate. I hope to start the next season with two colonies. I’ll be kicking myself if both colonies end up dying, that will be about 150 euro’s down the drain. I now know my original colony is still alive (because of the oxalic acid treatment I had to perform) but it wasn’t as large as I would have liked. And there are still 2 months of possible freezing weather ahead. If I were a religious man I would be praying, but me I’m just hoping for the best.