2 MILLION BLOSSOMS
Bees coated in powdered sugar to dislodge and then assess the colony’s population of varroa mites.
explored. At the top of the list is the question of resistance: are there indeed colonies resistant to varroa, that require no treatment, and if so, what are the mechanisms of resistance and why aren’t more beekeepers using resistant bees?
if it had brought that research into the video. A fair number of resistant colonies have been found at various locations globally, generally discovered from feral nests or abandoned apiaries, or else from researchers placing bees at isolated sites where selection proceeds unimpeded by management. Some examples of regions where naturally occurring or selected honey bee resistance to varroa was uncovered include (much of the information below is taken from a 2016 article by Swedish researcher Barbara Locke, in Apidologie 47:467–482): • Brazil and South Africa, with the African bee Apis mellifera scutellata;
• The island of Fernando de Noranha, with a hybrid ligustica/ scutellata cross from a Brazilian breeding program;
• Primorsky, Russia, a stock that was imported by the US Department of Agriculture to the bee laboratory in Baton Rouge, and through a selection program provided commercially available stock;
• Gotland, Sweden, from a diversity of honey bee races, showing 82 percent reduction in mite populations;
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• Avignon, France, from feral colonies, with 30 percent lower mite reproductive success; and
• Arnot Forest, New York, an isolated and genetically distinct feral population.
There also has been a fair bit of research into the mechanisms of resistance to varroa, and there are a number of traits through which Apis mellifera can resist mite infestations. It requires untreated colonies, however, for these traits to emerge, as treatment removes any selection pressure that might lead to resistance. And, the resistant honey bee populations that have been discovered express a variety of moderately effective mite-resistant characteristics rather than just one highly effective trait. Perhaps the most fascinating resistance mechanism is uncapping and recapping, where worker bees uncap cells and remove infested pupae, thereby preventing the adult mites from reproducing and immature mites from maturing to adulthood. Colonies with this trait uncap cells more frequently and target mite-infested cells more effectively than susceptible colonies. Cells uncapped without mites are recapped so that the pupae can still develop to adults. Grooming behavior is another mechanism, particularly
with the scutellata subspecies, as worker bees remove and kill adult mites infesting their colony mates. A third mechanism may be more at the colony-level, small colony size and frequent swarming, which breaks the brood cycle and reduces
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