Just received this from BIBBA (Bee Improvement and Bee Breeders Association
here in UK). Implies uncapping can kill the juvenile mites. Maybe bald brood
is not such a bad thing! Article was written by Kevin Thorn of BIBBA.

 


Two years  ago I listened to a talk by Professor Stephen Martin, a world
wide expert on Varroa, at the Cambridge BKA Convention.  He hinted at
research that would be published that would spell the end of the need to
treat Varroa. At the BBKA spring convention in April 2019 he was able to
elaborate further. His research team have found that honey bees in Africa,
South and Central America are Varroa tolerant (and Africanised!).
In the rest of the world while mites can reproduce 3 fold in worker brood
and 5 fold in drone brood the actual rate is 1.2x. The difference is due to
lack of fertility, accidents etc. In the Africanised bees the rate of
reproduction is 0.8x. This is significant as any ratio below 1x means the
mite population is reducing!
The Varroa tolerant bees showed an infestation rate of 4% whereas non
tolerant populations showed an average 27% infestation.
Enhanced grooming and hygienic behaviour was found to make little difference
but a third behaviour - uncapping and recapping has been found to be the
effective behaviour. In places where there is no Varroa there is no sign of
this behaviour. The bees were seen to uncap and recap several times. Where
mites are not present the bees had made a small hole and recapped. Where
mites were present they made a larger hole and recapped (- this can be seen
as a silvery sheen on the capping as this is part of the pupal cocoon). This
action exposes young mites and kills them and while the mother mite survives
she is unable to reproduce. This may also show up as pepper pot brood.
The key message was DON'T CHANGE YOUR CURRENT TREATMENT REGIME! If we stop
treating now we may create Varroa concentrations that could wipe out the
tolerant populations AKA Varroa bombs. The next stage of the research is to
look at how the average beekeeper can manage and select their colonies to be
able to take advantage of tolerant behaviour.
Perhaps not the end of Varroa but maybe the beginning of the end? 

John Macdougall, Hitchin, UK

 


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