A survey released this week by the Bee Informed Partnership, a collaborative organization of honeybee researchers around the country, revealed that beekeepers in the United States lost 44 percent of their colonies in the past year — the second highest annual loss reported in the past 10 years. Colony “losses” refer to colonies whose bees died from any number of possible reasons, such as disease. They do not necessarily refer to hives stricken by colony collapse disorder, which is a well-publicized but very specific phenomenon that occurs when a colony’s worker bees suddenly and mysteriously abandon the nest.
Notably, the survey indicated that bee losses during the summer were just as high as bee losses during the winter — an alarming finding, considering summer is the time of year when bees should be at their healthiest.
“The summer is boom time for bees — lots of forage,” said Dennis VanEngelsdorp, the survey’s project director and an entomologist at the University of Maryland. “We usually think of this as a very good time for bees. When we first started this [survey] 10 years ago, we didn’t even monitor summer losses because we didn’t think this would be significant.”
Altogether, the study surveyed more than 5,700 beekeepers managing nearly 400,000 honeybee colonies across the country. The findings indicated that about 28 percent of managed colonies were lost during both the 2015 summer and the 2015-2016 winter. Because beekeepers tend to add, remove or restore colonies throughout the year, these numbers come out to about a 44 percent loss of all colonies managed between April 2015 and March 2016.
A second survey, published Wednesday by the U.S. Department of Agriculture, supports these dire findings. Those results suggested that beekeeping operations throughout the country, maintaining five or more colonies at a time, lost anywhere from 12 to 18 percent of their colonies each quarter between January 2015 and April 2016.
Scientists say they think the losses stem from a variety of factors, some of which may be more prevalent than others.
“What we think from other surveys is there are three major drivers,” VanEngelsdorp said. “Pesticides, poor nutrition and, most importantly, parasites.”
In fact, VanEngelsdorp was involved with another recent study, published last month in the journal Apidologie, which surveyed bee parasites and diseases between 2009 and 2014 and provided some insight into what afflictions are the biggest problems for honeybees. The survey found that Nosema, a disease-causing fungus, and the Varroa mite, a parasite capable of carrying a variety of harmful viruses, both remain major problems among honeybee colonies. In particular, the study indicated that Varroa mites may be more prevalent than previous analyses have suggested, with their infestations peaking between August and November.
“Especially in the fall, over 50 percent of the colonies sampled had levels higher than we think [will] damage colonies,” VanEngelsdorp said. He noted that backyard beekeepers, in particular, who typically keep fewer than 50 colonies at a time, sometimes fail to treat their hives for mites — and this can contribute to the parasite’s spread.
“When those colonies die, they spread their mites to all the neighborhood bees,” he said.
He added that the mite’s role in commercial beekeeping operations — which are larger and typically stay on top of their parasite treatments — seems to be “a little more complicated,” and is more likely to combine with other factors that may contribute to the demise of colonies, including the effects of pesticides or poor nutrition.
At the end of the day, scientists generally believe that no single factor is causing the demise of honeybees in the United States — and recent efforts to help the insects recover reflect this view. Last year, for instance, the White House released its first National Strategy to Promote the Health of Honey Bees and Other Pollinators, a document that stressed the importance of increased research on the effects of pesticides and establishing larger areas of good-quality habitat for pollinators, such as bee and butterfly gardens in urban areas.
The strategy set a goal of bringing winter honeybee colony losses down to 15 percent within the next 10 years — although, as this week’s surveys suggest, summer losses are now deserving of equal, if not greater, attention.
In the coming weeks, the Bee Informed Partnership will continue to break down the results of the most recent survey in order to analyze whether any particular regions or types of beekeeping operations seem to be more affected than others and to examine the causes of death most suspected by beekeepers. Gaining a greater understanding of these kinds of trends is a matter of immense importance to agriculture, and therefore national food security, VanEngelsdorp said.
“One in every three bites we eat is directly or indirectly pollinated by bees,” he said. “Without honeybees we would not be able to produce apples and almonds and a lot of other berries and fruits, so it’s really important to understand the drivers of these losses.”