Managed honeybee colonies suffered annual losses of 42%, with summer declines outstripping winter losses for the first time, the U.S. Department of Agriculture reported Wednesday.
The declines are less steep than those associated with the mysterious widespread collapse of bee colonies, first recognized in 2006, but remain troublesome, driving up prices for crop pollination services, according to the department.
“Beekeepers in some cases are replacing half their operations during the year,” said Jeff Pettis, a senior research entomologist at the USDA Agricultural Research Center's Bee Research Laboratory in Beltsville, Md.
California has the largest number of beekeeping operations in the country. Its almond industry, the single largest user of honeybees, paid more than $292 million for pollination services in 2012, according to the USDA.
Prices for colony rentals for a three- to five-week pollination period ranged from $140 to $200 last year, depending on colony size, according to the online beekeeping community Beesource.com.
Summer colony losses averaged 27.4%, based on the agency's annual survey, which included more than 6,100 beekeepers managing 400,000 colonies — about 16% of the colonies managed nationwide.
The decline outstripped the 23% winter loss, according to the survey.
“We've always known that we had summer losses,” Pettis said. “We just never tried to quantify it before.”
Although winters are stressful for hived bees, spring and summer are the times when colonies are moved from crop to crop across multiple states.
“That pollination workload is certainly part of it,” Pettis said.
In addition to the summer losses, entomologists are puzzling over reports of unusually high rates of queen loss, which can doom a colony. “Queen honeybees are either dying in the colony or being replaced,” Pettis said. “They're failing for some reason.”
A 2012 USDA study attributed colony collapse disorder to multiple factors, including beekeeping practices, parasites, viruses and exposure to agricultural chemicals such as neonicotinoid pesticides.
Such stress amounts to “death by a thousand cuts” for bee colonies, said Gordon Wardell, pollination manager for Paramount Farms, which rents 90,000 colonies to pollinate its 46,000 acres of almond trees in the San Joaquin Valley.
“Commercial beekeepers are pushing their bees more,” causing imbalances in the social structure of colonies, he said.
That social structure, tightly regulated by chemical pheromones, is key to survival of a colony. Normally, a colony experiences rapid population growth that tapers off as winter approaches, Wardell said.
“They're keeping the bees in that exponential growth phase longer than they normally would be in it,” he said.
Because foraging bees survive only a few weeks, a colony can quickly collapse without adequate replacements.
A recent study showed that even a slight increase in forager mortality can cause a domino effect — worker bees become foragers too early in their life cycle, increasing their mortality, perpetuating the cycle that can cause colony collapse within months.
Even a weakened colony can drastically affect pollination, Wardell said.
“We had a real quick bloom this year; the bloom happened in about two weeks,” Wardell said. “And if you don't have real strong colonies, your flowers don't get pollinated.”
Pointing to the colony declines, environmental and food safety groups have been pushing to suspend or ban the use of neonicotinoid pesticides, commonly used to coat seeds.
“These dire honeybee numbers add to the consistent pattern of unsustainable bee losses in recent years that threatens our food system,” Tiffany Finck-Haynes, food futures campaigner with Friends of the Earth, said Wednesday.
The U.S. Environmental Protection Agency in April informed registered users of neonicotinoids that the agency is “likely not to be in a position to approve” new applications of the chemicals while it weighs the risk to crop pollinators.
The European Union banned use of several neonicotinoid chemicals two years ago, but their replacement with older pesticides has led to insect infestations in some crops.