>Are you saying breeding for hygienic traits?  How many generations?

By three generations of selecting for freeze-kill hygiene, the better
colonies easily passed a challenge of putting an entire box of AFB-infected
combs on them to clean up.  But it did not eliminate some residual spores,
so you might see a few diseased larvae at the next nutritional stress, but
they'd soon also disappear.

The colonies are resistant, not immune.

The rate at which you can breed for hygiene (and some other traits) depends
upon heritability and arithmetic.  If the trait is heritable, and you can
control matings, and apply rigorous selection, progress can be fast.  I've
seen this for ABF hygiene, tracheal mite resistance, chalkbrood resistance,
temperament, color, etc.  Noticeable improvement in as little as three
generations.

Unfortunately, resistance to varroa has proven to be more of a challenge...

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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