Honey bee colonies are still struggling to prevent increasing rates of losses, and the most recent survey shows U.S. beekeepers lost 44 percent of their colonies during the year between April 2015 and April 2016. What’s even worse is that the results showed rates of both winter loss and summer loss–and total annual losses—worsened compared with last year. This is the second year that summer loss rates rivaled winter loss rates.

A total of 44.1 percent of colonies were lost over the course of the year, which marks an increase of 3.5 percent over the previous study year (2014-15), when loss rates were found to be 40.6 percent. Winter loss rates increased from 22.3 percent in the previous winter to 28.1 percent this past winter, while summer loss rates increased from 25.3 percent to 28.1 percent.

The survey, Honey Bee Colony Loss, was released by the U.S. Department of Agriculture’s National Agriculture Statistics Service (NASS) and was conducted by the Bee Informed Partnership in collaboration with the Apiary Inspectors of America.

Both commercial and small-scale beekeepers were asked to track the health and survival of their honey bee colonies.

Figure 1: Summary of the total overwinter colony losses (October 1 - April 1) of managed honey bee colonies in the United States across nine annual national surveys. The acceptable range is the average percentage of acceptable colony losses declared by the survey participants in each year of the survey.

"We're now in the second year of high rates of summer loss, which is cause for serious concern," said Dennis vanEngelsdorp, an assistant professor of entomology at the University of Maryland and project director for the Bee Informed Partnership. "Some winter losses are normal and expected. But the fact that beekeepers are losing bees in the summer, when bees should be at their healthiest, is quite alarming."

The researchers note that many factors are contributing to colony losses. A clear culprit is the varroa mite, a lethal parasite that can easily spread between colonies. Pesticides and malnutrition caused by changing land use patterns are also likely taking a toll, especially among commercial beekeepers.

A recent study, published online in the journal Apidologie on April 20, 2016, provided the first multi-year assessment of honey bee parasites and disease in both commercial and backyard beekeeping operations. Among other findings, that study found that the varroa mite is far more abundant than previous estimates indicate and is closely linked to several damaging viruses. Varroa is a particularly challenging problem among backyard beekeepers (defined as those who manage fewer than 50 colonies).

"The high rate of loss over the entire year means that beekeepers are working overtime to constantly replace their losses," said Jeffery Pettis, a senior entomologist at the USDA and a co-coordinator of the survey. "These losses cost the beekeeper time and money. More importantly, the industry needs these bees to meet the growing demand for pollination services. We urgently need solutions to slow the rate of both winter and summer colony losses."