Scientists have been trying to discover why millions of beehives have collapsed and died during the past six years. The reason for the phenomenon - known as Colony Collapse Disorder - according to a new study, may be much more complex and disconcerting. Dozens of different types of chemicals may be combining to wreak havoc on the pollen that the bees collect for their hives.
CCD has killed off more than 10 million beehives in North America since 2007 alone. Scientists have tried repeatedly to identify the root cause for the beehive collapses, ranging from certain classes of pesticides to parasites or nutrition.
So academic researchers from the University of Maryland and federal scientists from the Department of Agriculture decided to collect pollen from seven major types of crops along the East Coast where CCD has been especially destructive - where bees had been in serious decline – and fed them to healthy bees.
The pollen fed to the healthy bees contained an average of nine different types of pesticides and fungicides. One pollen sample had 21 different chemicals.
The researchers discovered that the healthy bees that ate the fungicides – which are supposedly harmless to bees – were actually three times more likely to become infected with a parasite that's known to cause Colony Collapse Disorder, according to the study in PLOS One, an open access journal.
What the study also indicated is that there may not be a single cause of the collapse of bee colonies in North America – it could be a complex web of many chemicals that involves different types and classes of pesticides and fungicides.
Fungicides are used to control things like fungus on apples, and weren't expected to have an impact on healthy bees. But according to the study, healthy bees that ate such fungicides were much more likely to become infected with a deadly parasite. So USDA may need to change the way it regulates the use of such fungicides around these crops and the bee colonies that pollinate them, and change the way it advises farmers and beekeepers about the use of such fungicides.
Likewise, if CCD is linked to the complex array of chemicals in pollen, it will make it vastly more difficult to protect bee colonies – not to mention the implications for other forms of life subjected to this complex set of chemicals that make their way into the food web or environment.
And to make things even more complicated, the researchers found that the healthy bees they sampled had mostly foraged from weeds and wildflowers – not crops – meaning that bees in general across North America are likely much more exposed to pesticides than previously thought.
More research is needed about "how honey bees are exposed to pesticides outside the field in which they are placed. We detected 35 different pesticides in the sample pollen, and found high fungicide loads," the authors wrote in PLOS One. "Our results highlight a need for research on sub-lethal effects of fungicides and other chemicals that bees in an agricultural setting are exposed to."
CCD isn't just about the bees – food crops and agriculture economies are affected too. Because bee populations are so low in the United States, for instance, the surviving colonies are working overtime to pollinate crops in California and elsewhere. More than $30 billion worth of crops in the U.S. could be seriously at risk if the continuing die off of honeybees were to reach critical levels.
While the researchers were careful not to directly link the complex web of pesticides found in the pollen samples directly to Colony Collapse Disorder, the inference is hard to ignore.
It's also just common sense. Something has been causing CCD in different parts of North America, and it would make sense that chemicals designed to kill certain things like pests or weeds might also have unintended consequences when combined and spread outside crops.
The solution could be as simple as labeling fungicides that kill fungus on apples, for instance. But it could also be vastly more complicated, and involve tighter regulation of the regions and instances where different sets of chemicals are used in and around crops pollinated by honeybee colonies.
Right now, for instance, pesticide labels tell farmers not to spray when bees are known to be pollinating, but those regulations don't apply to the chemicals used to kill fungus on the crops and were thought to be harmless to bees.
But one finding from the study that beekeepers should consider right away is that simply looking at the types of chemicals used on crops may simply not be enough.
"Our results show that beekeepers need to consider not only pesticide regimens of the fields in which they are placing their bees, but also spray programs near those fields that may contribute to pesticide drift onto weeds," the authors wrote. "The bees in our study collected pollen from diverse sources, often failing to collect any pollen from the target crop."
And the study also points out what we don't know, and need to study more closely. "Given the diverse routes of exposure to pesticides we show, and increasing evidence that pesticide blends harm bees," the authors wrote, "there is a pressing need for further research on the mechanisms underlying pesticide-pesticide and pesticide-disease synergistic effects on honey bee health."