Last winter, 29 percent of hives in the U.S. succumbed to colony collapse disorder Suspected causes are mites, stress from shipping bees long distances to their pollinating locations and viruses, the Fort Worth Star-Telegram reported Sunday.
One researcher at Penn State University believes the main problem to be pesticides.
"We do feel like pesticides are playing a role in pollinator decline. We know that the pesticides are there. We don't know yet exactly what role they're playing," Maryann Frazier said.
The environmental group, the Sierra Club, suspects chemically coated seeds called neonicotinoids, an artificial form of nicotine, to be the problem, the Star-Telegram said.
They have asked the Environmental Protection Agency to suspend use of the seeds until more research can be conducted.
Bees are shipped nationwide to pollinate crops such as vegetables, fruits and nuts. They are essential to U.S. agriculture adding $15 billion to the value of those crops, the newspaper said.