A new U. S. study has detected a number of pesticides in North American honeybee colonies at far higher levels than previously known.
Scientists have found “unprecedented levels of miticides and agricultural pesticides in honeybee colonies from across the U. S. and one Canadian province,” says the study, published March 19 in an online scientific journal.
The study by a team of Pennsylvania State University entomologists is careful to avoid saying chemicals cause colony collapse disorder (CCD), a mysterious die-off of bees occurring throughout the U. S. But it refuses to dismiss the idea, either.
“It seems to us that it is far too early to attempt to link or dismiss pesticide impacts with CCD,” the study says.
CCD has become a metaphor for recent massive losses of honeybee colonies in the U. S., Canada and Europe. The U. S. lost a third of its bee colonies in each of the three winters between 2006 and 2009.
Across Canada, beekeepers during the winter of 2009 averaged colony losses of nearly 35 per cent.
Scientists looking for a smoking gun to explain the losses have concluded they are due to a combination of factors. That could include chemicals in hives.
The “plethora of pesticides that are currently present in U. S. beehives” calls for urgent action, the study’s authors say.
They call for “urgent changes in regulatory policies regarding pesticide registration and monitoring procedures as they relate to pollinator safety” in order to safeguard the food supply.
“Is risking the $14 billion contribution of pollinators to our food system really worth lack of action?” the writers ask in conclusion.
The study based its findings on 749 samples of pollen and beeswax taken from commercial bee operations between 2007 and 2008.
Researchers call it the largest sampling to date of pesticide residues in bee colonies in North America or worldwide.
In all, the study detected 118 different chemicals in the samples, with an average of seven different products per sample.
The wax samples contained traces of 87 different pesticides, averaging eight different residues in each sample. The pollen samples contained 98 pesticides with up to 31 different pesticides in a single sample and an overall average of seven per sample.
The most frequently found residues were from fluvalinate and coumaphos, chemicals used to control the parasitic varroa mite endemic in North American bee hives.
A list of the top 10 detected products includes: three in-hive miticides, five insecticides, one fungicide and one herbicide.
This suggests the bulk of chemical residues in bee colonies stem from efforts to control the varroa and other insect pests.
But it also indicates bees pick up agro-chemicals along with pollen while foraging and bring them back to their hives.
Beeswax is the least renewable resource in a hive and “is thus where persistent pesticides can provide a ‘toxic-house’ syndrome for the bees,” the study says.
Heather Clay, CEO of the Canadian Honey Council, described a recently discovered phenomenon called “entombed pollen” in which bees brick up pollen they’ve collected so it’s not available. Subsequent tests show high levels of agricultural chemicals in the pollen.
It’s believed bees know they can’t use the pollen because it’s contaminated, Clay said.
The higher-than-expected prevalence of chemicals in bee colonies is significant but not conclusive toward explaining high rates of bee colony losses, she said,
“It’s one more arrow in the quiver but it’s certainly not the whole story. It’s just one thing that might be weakening the bees’ immune system.”
David Ostermann, a Manitoba Agriculture, Food and Rural Initiatives apiarist, said recent research at the University of Guelph suggests the presence of the varroa in hives is the main reasons for bee losses.
He suggested beekeepers can use “softer” products or replace comb more frequently to mitigate pesticide residues in hives.