On Tue, 17 Mar 2009 08:21:45 -0600, allen <[log in to unmask]> wrote:

>> True, and in operations or yards where varroa are not adequately
>> controlled in time, the strongest colonies one year are most likely to be
>> the dinks (or dead) the next spring.  IMO, an operation raising its own
>> queens should keep at least some of the dinks because their queens contain
>> valuable genetics (as evidenced by colony strength and production in the
>> prior year).

>I wondered about that and think a lot depends on your goals in breeding,
>your point in the progress towards those goals, whether you have -- or are
>close to having -- hives that do not need treatments -- and the design of
>your breeding programme. 
>
>Bob was talking about how commercials cull, and I agree: 'no mercy' when it
>comes to deciding which hives get to breed.

Bob and Allen are making very good points that are especially applicable
when the mite control method achieves very high colony survival rates or the
strain of bees has very high varroa tolerance.  My breeding program lets
winter plus varroa cull 25% of my colonies.  If actual mortality is 10%, I
choose another 15% from what I view as the worst weak ones/dinks.  If actual
mortality is near 25%, I keep nearly all the dinks.  I will point out that
it is very difficult to know in advance how much to back off on mite
treatment so that dead plus dinks equal 25%.  I cannot afford a 50-75%
colony loss and still meet my commitments.  On the other hand, a 0-5% loss
rate means there is inadequate selection pressure.

I believe the nature of varroa leads to an inherent contradiction in a
breeding program.  A strain of bees that keeps small populations, and swarms
often, will show a lot of varroa resistance.  Beekeepers want large
populations and minimal swarming in order to get large honey crops.  In the
moderate selection pressure breeding program I use, I am worried about
selecting against productive colonies and selecting against colonies that
happen to have more drone comb.  I should know in a few years whether I am
attempting the impossible.

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