Modelling the spread of resistance to Varroa in Australian feral honeybee populations

Abstract

Australia is the only country where Western honeybees, Apis mellifera, are not infested with the mite Varroa destructor. Hence, a collapse in the feral honeybee population, brought about by an incursion and spread of V. destructor, would have serious consequences for Australian horticulture given its dependence on managed and feral honeybees for pollination. Managing Varroa in commercial colonies is well understood and can be achieved, although at significant bee-health costs, by using miticides. Protecting the feral population in the event of a Varroa incursion is much more difficult, but nevertheless imperative. One way to mitigate against collapse of the feral population is to seed it with Varroa-resistant queens, so as to accelerate the spread of resistance. We developed a simulation model of the spread of Varroa-resistance in feral honeybee populations following the introduction of Varroa-resistant queens into the managed population. We show that, compared with a do-nothing scenario, seeding the managed honeybee population with Varroa-resistant queens was only effective in decreasing the length of time for the feral honeybee population to recover when the size of the managed resistant population was large compared to the size of the feral population. This situation may be achievable in some urban areas where numbers of managed colonies are high and habitat for feral colonies is limited.