Do Varroa Manipulate Honey Bee Behaviour?
New research from the Carl Hayden Bee Research Center in Arizona considers whether Varroa mites and viruses are changing honey bee behaviour to improve parasite dispersion in the landscape.
The scientists conducted a longevity study in which multiple miticide treatments were applied to the colonies. However mite numbers remained high and colony losses exceeded 55%. High mortality from Varroa in managed apiaries is a departure from the effects of the mite in feral colonies where bees and Varroa can coexist. The research considers whether differences in mite survival strategies and dispersal mechanisms may be contributing factors. In feral colonies, mites can disperse through swarming. In managed apiaries, where swarming is reduced, mites disperse on foragers robbing or drifting from infested hives. Could the high density of commercial colonies and the management practices to reduce swarming be driving greater exchange of Varroa between colonies? The team used a honey bee–Varroa population model to show that yearly swarming curtails Varroa population growth, enabling colony survival for more than 5 years. However without swarming, colonies collapsed by the third year. To disperse, Varroa must attach to foragers that then enter other hives. The research considers whether stress from parasitism and virus infection combined with effects that viruses have on cognitive function may contribute to forager drift and mite and virus dispersal. Also could drifting foragers with mites can measurably increase mite populations. The simulations indicated that low levels of drifting foragers with mites can create a sharp increases in mite populations in autumn and heavily infested colonies in the spring.
Read the full paper.