A new study by researchers from the Harvard School of Public Health says that the widespread demise of honeybees is due to the use of a class of popular insecticides called neonicotinoids, combined with cold temperatures during the winter months. The study is published online in the Bulletin of Insectology.
The deadly combination of insecticides and cold weather causes honeybees to abandon their hives–a phenomenon known as Colony Collapse Disorder (CCD). Over recent years, Western countries have lost between 30 percent and 70 percent of their honeybee populations, scientists say.
The new study replicates earlier research by same research team that found a link between CCD and low doses of imidacloprid, another neonicotinoid insecticide.
“We demonstrated again in this study that neonicotinoids are highly likely responsible for triggering CCD in honeybee hives that were healthy prior to the arrival of winter,” said lead author Chensheng (Alex) Lu in a statement.
Lu’s group studied the health of 18 honeybee hives in three separate locations in central Massachusetts from October 2012 through April 2013. At each location they separated six colonies into three groups, one treated with clothiamidin (another neonicotinoid), one treated with imidacloprid, and another left untreated.
The researchers observed a steady decline in the size of honeybee colonies treated with insecticides. By April 2013, six of the 12 neonicotinoid-treated colonies had abandoned their hives. Only one of the control colonies was lost, the study says.
So what is the big deal? The sharp reduction in honeybee populations is worrying because bees are responsible for pollinating about a third of the world’s crops, with some saying that in the United States, honeybees pollinate as much as 80 percent of agricultural crops.
Although Lu’s team has shown a strong correlation between the use of neonicotinoids and CCD, they do not yet know what it is about exposure to these chemicals that causes bees to leave their hives.
“Although we have demonstrated the validity of the association between neonicotinoids and CCD in this study, future research could help elucidate the biological mechanism that is responsible for linking sub-lethal exposures to CCD,” Lu said. “Hopefully we can reverse the continuing trend of honeybee loss.”
The massive population decline has led some to speculate that Congress may consider tightening regulations of pesticides linked to CCD. Calls for action are already building at the state level. Earlier this month, the Oregon Association of Nurseries urges Congress to use a collaborative and scientific approach to regulating pesticides that some blame for honeybee deaths.
“This chemical class, when used properly, is vital to the success of our industry,” said OAN director Jeff Stone told members of the House Agriculture Subcommittee on Horticulture, Research, Biotechnology and Foreign Agriculture.
While CDC may eventually spur members to find a solution, a number of lawmakers have expressed little interest in addressing an issue that is likely to pit environmentalists against agriculturalists.