Maryland's beekeepers lost nearly 61 percent of their colonies on average in the past year, one of the highest declines in the nation, according to an annual survey released by the U.S. Department of Agriculture.
Summer bee die-offs in the state and nationwide outstripped winter losses for the first time, surprising scientists involved in the survey. A University of Maryland entomologist who helps coordinate the survey said parasites remain a top suspect in the bee declines but suggested changing farming practices and pesticide use also may be factors, at least nationally.
Environmentalists called for renewed scrutiny of a widely used group of pesticides linked in some research with bee declines. A key Maryland lawmaker promised an investigation.
Nationwide, managed honeybee colonies suffered annual losses of 42 percent, according to the survey, up from 34 percent the previous year. Winter losses, which had been the focus of concern about "colony collapse disorder" several years ago, declined — though they remained higher than what many beekeepers consider acceptable.
But the surprising finding was that keepers reported losing an average of 27.4 percent of their colonies last summer, topping the winter loss rate.
The declines appear to be driving up prices for crop pollination services, according to federal agriculture officials, a trend beekeepers say is likely to put upward pressure on food prices, especially fruits.
"If you've ever eaten a strawberry or a blueberry, you ought to thank a bee," said Toni Burnham, president of the Maryland State Beekeepers Association.
In Maryland, beekeepers reported losing 44 percent of their hives on average last summer and 41 percent over the winter, said Dennis vanEngelsdorp, an assistant professor of entomology at the University of Maryland, College Park. He is project director for the Bee Informed Partnership, a coalition of scientists and government officials studying bee health issues.
Maryland beekeepers' overall loss rate of 60.9 percent was fifth-highest among all states, the survey found.
State agriculture officials were not available to comment on the survey, but Julie Oberg, spokeswoman for the state Department of Agriculture, said Maryland honeybees are under a variety of pressures, including "the destructive Varroa mite, pathogens, nutrition and habitat loss."
There are about 900 beekeepers statewide, tending to 9,000 colonies, she said, and most are small-scale or backyard operations.
Varroa mites are a chief suspect in many beehive declines, vanEngelsdorp said, and many backyard beekeepers don't treat their hives for mites as often or as regularly as large-scale commercial operations.
But vanEngelsdorp said this survey found even big commercial beekeepers reported high summer losses, which he called "a real shocker."
"While we think Varroa mites probably played a role there, too, we have to think other things are at play," he said.
He suggested one factor may be changing farming practices, with vast acreage planted in corn, soybeans and other crops that do not provide bees the same nutrition. And he said scientists also are looking at whether pesticide use on farms could be playing a role.
A number of studies have found that neonicotinoid pesticides, widely used in farming and in home gardening products, may be linked to deaths of honeybees as well as wild bees and other pollinating insects. Even at doses too low to kill outright, the chemicals have been found to impair bees' performance.
VanEngelsdorp said he suspected other pesticides, though he declined to name any. He said he didn't see evidence that neonicotinoids, if properly applied on farm fields, would be enough to kill off honeybees — though he said they might be doing so to wild pollinators.
Burnham said she believed frigid weather this past winter and early spring played a role in winter bee losses. Mites also are undoubtedly a major factor, she said, but she suggested that pesticide use, including the neonicotinoids, adds to a growing variety of environmental insults and stresses with which managed honeybee colonies must cope.
"They can fend off one thing more easily when they aren't fending off a dozen other things," Burnham said.
Environmentalists and many beekeepers lobbied unsuccessfully in Annapolis this year for legislation that would have barred retail sale of neonicotinoid pesticides and required labeling of nursery plants that had been treated with them. State agriculture officials and others argued the restrictions would hurt farmers and nurseries, and were unwarranted given other research disputing the pesticides' impacts on bees.
Ruth Berlin, executive director of the Maryland Pesticide Education Network, said she hoped lawmakers would revisit the issue next year, especially given the new survey results.
Manufacturers of neonicotinoid insecticides defend their products, citing studies that have shown they will not harm bees when used as directed.
Del. Kumar Barve, chairman of the House Environment and Transportation Committee, said his panel intends to investigate the reasons behind the losses. The Montgomery County Democrat said lawmakers heard conflicting testimony about the status of the state's beekeeping industry, "but the majority seems to show it is under real pressure."
Tribune Newspapers contributed to this article.