Re. "I believe Thunder Bay, Ontario, Canada beekeepers are finding it impossible to maintain their mite free status thanks to the drift off trucks carrying mobile bee stocks. There is not an alternate route: if I were a Thunder Bay beekeeper I would run with robbing screens on."

I've spoken with four Thunder Bay beekeepers about their Varroa history.  They lost their Varroa-free status in 2012.  Although prior to 2012 they were concerned about drift from migratory stocks transported along the Trans Canada Highway (something the provincial government would not restrict), they attribute their first Varroa incursions to the actions of one or two beekeepers who violated their voluntary quarantine.  They had invested a great deal of energy as a beekeeping community in trying to maintain a quarantine re. importation, but their own members crashed it, with predicable results.

I note, however, that there appears to have been a Varroa-related drift problem associated with migratory beekeeping along "principle highway(s)" between B.C. and Alberta in the early 1990s, soon after the first Varroa incursions in B.C.  Provincial apiarist, Paul van Westendorp, reported this in the 1994 CAPA Proceedings (p.15): "In the spring of 1993, one commercial producer moved an estimated 700 lightly Varroa infested colonies from the south Okanagan Bee District to the (Alberta) Peace River without netting or closed entrances during daytime hours. The beekeeper has been charged by BC for moving bees illegally (still pending) and charged and convicted in Alberta for importing bees into the province illegally.  Subsequent Varroa infestations have been found along the principal highway(s) leading to Alberta. Currently, most mite infestations are found in border areas, while the majority of colonies remain mitefree."

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