There was an interesting set of mails today with several subject headings but
connected with varroa mites, treatments and selection.  One of the simple
experiments that hobby beekeepers could do on all their hives and commercial
beekeepers could do on a similar quantity but smaller proportion is to use mesh
floors to monitor natural mite drop.

At it's simplest this can tell the keeper to treat or to leave alone, thus
reducing routine treatments.  The mesh floor can easily pay for itself in a
couple of seasons in this way.  The reduction in treatments can prolong the
effective life of chemicals for those who choose to use them, or to indicate that it
is time to take physical or biological treatments for those who do not or who
wish to alternate methods.

An interesting experiment that I did (24 hour mite drop at monthly intervals)
was not just to count naturally fallen mites but to look at them through a
10X lens.  I found that over a period of several months the proportion of
naturally fallen mites with missing legs or with dents in the carapace increased
markedly, although not enough to cope with the increase in mites.

This suggests to me that this is an indication that 'aggressive grooming', if
that is the appropriate term, is learned behavior rather than inherited.
From this it follows that it may be useful to maintain a proportion of mites in a
hive so that learning is not forgotten.  I suppose one could do parallel
counts on a number of hives to determine whether some are better at aggressive
grooming than others or learn faster. If so then selection might be possible and
useful.

Chris

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