The US National Honey Bee Disease Survey sampled colony pests and diseases from 2009 to 2014. Even with increased focus on improving honey bee health, winter colony losses have averaged ~30 % over the last 8 years and annual hive mortality approached 50 % for commercial beekeepers

From September through November, only 30–45 % of samples tested were below the three-mite threshold. Thus, more than half of all beekeepers surveyed entered the winter with elevated mite infestations, which have been shown to contribute significantly to winter colony mortality.

National winter loss surveys indicate that 60 % of hobby beekeepers do not treat for Varroa. Without beekeeper Varroa management interventions, these colonies almost inevitably crash, releasing abundant mites that invade healthy colonies by switching from nurse bees to foragers and swapping hosts via communal foraging or robbing.

Traynor, Kirsten S., et al. "Multiyear survey targeting disease incidence in US honey bees." Apidologie (2016): 1-23.

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