Alyn W. Ashworth wrote:
 
An additional technique is to trap the Q on a frame of drone comb, caged
in with excluder-type walls, so that she only lays drone. When the comb
is full (sealed?), transfer the Q to another similar frame trap, destroy
the first and repeat. I think that the idea is to make sure that the
only available cells for the varroa are those within the special frames,
so that a large proportion are destroyed.
 
We don't (yet, quite) have the dreaded mite here in Liverpool, but
perhaps someone with practical experience could enlarge on this
treatment and it's pros & cons - looks attractive, but may be a lot of
work for anyone with more than a couple of hives.
 
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Methods of 'comb trapping' varroa mites  have been used quite widely in
Europe, and properly carried out can remove up to 90% of mites from a
colony. It is not necessary to use drone comb in the comb-cage, and if you
do you tend to find the queen does not lay properly. Worker comb is much
better; the important thing is that the only young brood available to mites
wishing to reproducein in the trap combs during the month or so the method
is in use.
 
The other important point concerns timing. Since the colony will not be
producing new bees for a month, if practised too early it will harm colony
build-up for the honey flow, and if practiced too late, it will harm colony
preparations for winter. Here in Europe, there is a suitable window between
the point at which further eggs laid will not contribute foragers in time
for the main flow (around the start of June) and the point when colonies
start cutting back for winter (around the beginning of August).
 
Comb trapping methods are very labour intensive and probably not really
suitable for the large scale beekeepers. Despite this, they have their
place reducing the use of chemical treatments as part of an integrated
varroa control programme.
 
James Morton
CSL Regional Bee Inspector (S.E England)