I want to clarify somewhat the comment in the text about the contradiction concerning the reason for lowering the threshold for giving Thymol to get a better selection. At the same time saying that if you have non-selected bees against Varroa resistance it might be good to have a low threshold to avoid loosing many colonies.

But first I think it’s good to mention that the “selection average” concerning the crop for all apiaries is not a real average. The economical average, the total crop harvested, divided by all colonies wintered in the autumn, has been for a number of years between 25 and 35 kg (55-77 lb). That is including all colonies lost during winter and all colonies for different reasons not producing or producing very little.

When Varroa started to create problems (2008 – and arrived a couple of years before) I lost quite many colonies the first two years. That’s not uncommon. Common is also to continue to lose many colonies in intervals with some years in between, in spite of heavy treatment.

During those problem years I made quite some walk away splits of the best survivor colonies in spring. They made their own queens to ensure to save survival heritage from those surviving colonies. But some of them of course survived due to treatment, and those still had low resistance.

After a couple of years, the winter losses have been about 15 % with another 30 % not producing or producing just a small crop. When I got the first colony that had been without Thymol for at least one season as a big colony (H157) I grafted a lot from it. But I hadn’t time to shift queens in all colonies, which had got most of Thymol. Such colonies that didn’t get their queens shifted unfortunately still contributed with drones coming season. But they contributed though to high genetic variation. The compromise was relevant to be able to produce enough much honey to put food on the table and keep me going.

Now the amount of resistance is better in my bee stock and next year I will have time to shift all queens needed. Maybe one third is the right number to avoid loss of genetic variation. If so the development might turn backwards. With a lower threshold now, the progress for the whole stock will accelerate, as the very best breeders will be easier to discern. And the Varroa population will be kept at a lower level and thus I will hopefully get a higher total crop.

But with unselected stock you may need the low threshold to avoid loosing many colonies. Probably some other help to discern breeders is necessary. When some progress is achieved it might be relevant to have a higher threshold than just one wingless bee. But be prepared for eventual more losses. Maybe the right time is when you can observe bees cleaning out infested brood and throwing out sick bees from the hive (mostly wingless bees), treating them as trash (they can even fly away with them to get them away from the hive). This is apparently a way for the bees to lower the virus pressure in the colony.

Comment to evaluation