Associated Press
A new federal report blames a combination of problems for a mysterious disappearance of honeybees.

WASHINGTON (MCT) — It's one of the most perplexing environmental mysteries of recent years: Why are honeybees dying, and what can be done to stop a catastrophic agricultural disaster with far-reaching economic and environmental consequences in the United States and beyond?

Scientists don't yet have a definitive answer. But a U.S. Department of Agriculture and Environmental Protection Agency report issued Thursday suggests a complex mix of problems contributing to honeybee colony declines, which first emerged in 2006. Contributors include parasites and disease, genetics, poor nutrition and pesticide exposure, as well as farming practices that don't give bees a pesticide-free buffer zone to forage in heavily developed agricultural regions.

"Modern farming practices are leaving very little room for bees and other pollinators at this moment," Sonny Ramaswamy, director of the USDA's National Institute of Food and Agriculture, said in a conference call explaining the report.

The report warns that even with intensive research to understand the cause of honeybee colony losses in the United States, losses continue to be high and could pose a serious threat to meeting the pollination demands for some commercial crops. Growers in California have had trouble pollinating almond trees in the winter, for example, and blueberry farmers in Maine face similar pressures.

"We're on the brink. I don't know that we've crossed that threshold yet, but we're certainly getting there very fast," said Idaho-based beekeeper Zach Browning, who joined USDA and EPA officials in announcing the report.

His 2012 colony losses were double what they were in 2011, said Browning, who co-owns one of the country's largest honey producers. The producer lost bees to drought, pesticides and hives that didn't have enough to eat, he said.

But it's pesticide use that has drawn the most interest in recent months, and some researchers and beekeepers fear Thursday's report didn't emphasize enough the possible effects of the widespread use of a class of pesticides known as neonicotinoids.

"I think it really downplays the effects of pesticides," said Jeff Miller of the Center for Biological Diversity, an Arizona-based nonprofit group, which has sued ? unsuccessfully so far — to force the EPA to consider the effect of pesticides on endangered species when it authorizes or reauthorizes pesticide use.

"There's some pretty strong links now, especially to the neonicotinoid pesticides and colony collapse disorder," Miller said in an interview. "There's some science showing that pesticide impacts may be increasing vulnerability to disease."

Officials in the European Union this week voted to move toward a ban on three popular pesticides in an effort to restore honeybee populations. In the United States, environmentalists and beekeepers have sued the EPA to stop the use of some of the pesticides.