Word is, in a nutshell, that SMR bees are actually hygienic bees, but with
an important difference.

SMR bees perform right up there with the HYG strains in standard HYG tests,
however, hygienic abilities observed in bees selected for SMR extend beyond
simply detecting and removing dead brood.  In addition to doing equally well
as HYG in detecting and removing dead brood, SMR bees are able to detect,
uncap, and remove foundress varroa mites that are laying eggs and
reproducing in cells.

This uncapping and removal liberates the foundress, interrupts her
reproductive work, and prematurely exposes the undeveloped offspring,
resulting in the death of the daughters.  The foundress may then enter
another cell, but, if she tries to reproduce there, the cycle repeats.  Thus
SMR greatly reduces mite reproduction, and mites die of old age or accidents
without replacing themselves.

The wrinkle is that these bees seem to be much less inclined to uncap and
remove foundress mites in sealed brood that are -- for whatever reason --
not laying eggs, and in any hive with varroa, there will be a considerable
percentage of mites that non-reproductive, but which are just sitting out
the dance in sealed in cells with the pupae.

These non-reproductive mites enter the cell, stay the duration of the
capping period, then emerge with the bee.

This subtle fact -- that SMR bees quickly and efficiently remove reproducing
mites in brood, but ignore non-reproductive mites in sealed
brood --initially escaped researchers, and obscured the strong similarity
between SMR and HYG.

Researchers finding and observing the varroa in the sealed brood of such
colonies concluded (understandably) that the bees were causing mite
non-reproduction, rather than realising that the bees had already located,
uncapped and pulled out most of the reproducing foundresses, leaving only
the non-reproducing mites.  After all, they would pull a frame of brood,
brush off the bees, then go to the lab and look at the brood and mites in
cells under magnification.  Sure there were a few empty cells, but there
always are.

They observed that a high percentage of foundress mites discovered in sealed
brood were non-reproducing, and that there were fewer mites -- as a
percentage of total mite load --in brood than expected.  They bred for this
characteristic, and actually wound up with an hygienic bee, but one with
special abilities -- the ability to sniff out and eject reproducing varroa
mites in sealed brood.

Current work -- if I understand correctly -- seems to indicate that SMR and
existing HYG cross well, and that the SMR characteristic can be transmitted
relatively easily to current HYG stock, so we may see some interesting
things in the near future.  A name change for SMR may be in the offing as
well.

FWIW, preliminary DNA work _seems_ to indicate that just two genes are
associated with SMR, but when asked if they are the same genes that are
associated with HYG, the answer from those working hard on this problem,
seems to be that no one knows yet, and that there is likely more to the
whole picture it than just two genes.

I might mention that Dee has been saying for a long time that Lusbys' bees
remove varroa foundresses, and that this is a major mechanism in the Lusby
success.  I think -- correct me if I am wrong -- that she also believes that
using small cells (4.9) encourages that trait.  I have heard others, here
and there, some with small cell and some with ordinary cells, observing
varroa removal, too.

This new(?) information is especially interesting for those of us who think
we can breed bees by looking at natural drop boards and rejecting hives with
big drops.  It is not that simple.  We could be rejecting the best varroa
fighters, using that criterion, if they are, at that moment, combating an
infestation originating outside the hive.  Observations over a longer period
are necessary to get an understanding.  (Again, credit to Dee for that).

Interesting!

allen
A Beekeeper's Diary: http://www.honeybeeworld.com/diary/

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