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Date: | Fri, 3 May 2019 08:00:46 -0600 |
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The resistance/tolerance (two different phenomena) of
African/Africanized bees is not as clear cut as many think. And even
murkier is the question of what mechanism(s) may have the greatest
effect in curbing varroa mites. The advancing front of Africanized
bees through northern South America, Central America, and even into the
USA did not carry or encounter varroa until after the bees had been
in each country for some time. So what emerged in Brazil as
resistance/tolerance may have occurred there and not in other
countries. The real (or perceived) need to treat confirms this view:
Brazilian beekeepers in general do not treat, in other countries they
claim to have to treat or varroa will take over. Puerto Rico seems to
have developed a unique subtype of Africanized bees- gentler, and not
requiring treatment.
As for mechanisms, the literature from Brazil documents a number of
mechanisms (infertility of mites in brood, grooming,
uncapping/recapping, generalized hygienic behavior), as isolated
reports, but as best as I know no one has looked at them in concert to
extract the relative contribution of each one. E. Guzman-Novoa did
that in Mexico and found no single strong mechanism. In terms of the
effect of uncapping/recapping in reducing mite growth in colonies, the
effect on reproduction is relatively small, at least relative to the
effect of highly specific removal of infested worker brood cells at the
level of colonies with VSH (varroa sensitive hygiene).
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