>>www.russianbreeder.org>... members of the 
association all agree not to use any kind of treatments for mites (both Tracheal and Varroa). That mindset of "only the strong survive" seems guaranteed to keep that particular trait in their lines of bees.

This is a good approach but they are at the *mercy* of the local drone population.  One would have to keep many (hundreds I suspect) hives in several adjacent apiary sites to ensure their virgins mate with mostly the drones from the same line to pass on the desirable traits.

In collecting many ferals, I find mostly robust colonies but there are a couple every year from one certain area that are declining from varroa.

In raising queens from my best ferals, I have been happy with their ability to go through the year well with only oxalic dribble in the early winter.  However, since I introduced the unlimited broodnest in my hives, I've seen a great increase in worker numbers and roughly doubling of the honey yield along with a decline of the production colonies at the end of the year (Nov./Dec.).  The nucs come through great though.

It's probably due to an increased varroa pressure in expanded brood rearing in the unlimited production colonies or from a change in the drone composition in the surrounding area.  Just have to keep selecting from the best.

Waldemar

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