Leif Hjalmarsson at his 3 km isolated apiary with Elgon colonies since established in 1998. Here he kept 5-7 colonies without treatment until he died in 2016.
• Few colonies in apiaries
I designed my apiaries with fewer than previously used number of colonies, sometimes only one.
In those with only one colony I had moved colonies that had needed some treatment, but not full dose. The following years they didn't need any treatment any more. It was 2 km (1,5 mile) to other apiaries. The distance that bees normally fly in whatever activities they are involved in, for example so called quiet robbing is mostly that distance.
The experiences from the above tested points give good advice for designing good circumstances for developing a resistant bee stock.
• Move the most inferior colonies away
Inspired by Eric Erickson,
the most inferior colonies concerning resistance (as well as bad temper, low crop, development, etc) were moved to a couple of apiaries furthest away from my other colonies. This took place first time just receently, but had a tremendous effect on lowering the average varroa level in the colonies. In the season 2020 only 20% of the colonies were treated (about 45% the year before). Most of the treated ones only got ¼ – ½ of a full thymol treatment, which now is 20 gram [2x5gr (x2)] not 30-40 gram as it was 10 years ago.
These far away apiaries are situated in a forested area with only those colonies. Four colonies in one, and three colonies in the second. Surprisingly these colonies that had been treated full doses the year before, now developed only low varroa levels. I had expected that I would loose some of them, but I didn't. Half of them were treated with 5-10 gr thymol (thymol pads). The other half nothing.
• Make splits from the best
After seeing that colonies that I had to treat with a full dose of thymol, and requeened them next year with a grafted queencell, they still often had to be treated effectively as virus effects were seen. This could go on for several queen replacements with grafted queens (and superseded ones).
So I decided to make splits if possible only from colonies that had not been treated for varroa, or treated very little. Such splits many times were allowed to produce their own queen. They were seldom needing any treatment.
The conclusion is that chemical (organic and other) treatments make the bees more susceptible for pathogens, such as viruses. In this case especially Deformed Wing Virus (DWV). And that it takes time for the microbiome to come back into harmony. The new queen has to get a very good set up of resistance traits in her worker bees to overcome the difficulties of the microbiome getting back to normal.
• VSH (Varroa Sensitive Hygien)