A national survey of managed honey bee 2014-2015 annual colony losses in the USA

Declines of pollinators and high mortality rates of honey bee colonies are a major concern, both in the USA and globally. Long-term data on summer, winter, and annual colony losses improve our understanding of forces shaping the viability of the pollination industry. Since the mass die-offs of colonies in the USA during the winter of 2006-2007, generally termed Colony Collapse Disorder (CCD), annual colony loss surveys have been conducted. These surveys gage colony losses among beekeepers of all operation sizes, recruited to participate via regional beekeeping organizations, phone calls, and postal mail. In the last three years, these surveys include summer and annual losses in addition to winter losses. Winter losses in this most recent survey include 5,937 valid participants (5,690 backyard, 169 sideline, and 78 commercial beekeepers), collectively managing 414,267 colonies on 1 October 2014 and constituting 15.1% of the estimated 2.74 million managed colonies in the USA. Annual losses are typically higher than either winter or summer losses, as they calculate losses over the entire year. Total reported losses were 25.3% [95% CI 24.7-25.9%] over the summer, 22.3% [95% CI 21.9-22.8%] over the winter, and 40.6% [95% CI 40.0-41.2%] for the entire 2014-2015 beekeeping year. Average losses were 14.7% [95% CI 14.0-15.3%] over the summer, 43.7% [95% CI 42.8-44.6%] over the winter, and 49.0% [95% CI 48.1-50.0%] over the entire year. While total winter losses were lower in 2014-2015 than in previous years, summer losses remained high, resulting in total annual colony losses of more than 40% during the survey period. This was the first year that total losses were higher in the summer than in the winter, explained in large part by commercial beekeepers reporting losses of 26.2% of their managed colonies during summer, compared to 20.5% during winter. Self-identified causes of overwintering mortality differed by operation size, with smaller backyard beekeepers generally indicating colony management issues (e.g., starvation, weak colony in the fall), in contrast to commercial beekeepers who typically emphasize parasites or factors outside their control (e.g., varroa, nosema, queen failure). More than two-thirds of all beekeepers (67.3%) had higher colony losses than they deemed acceptable.