SILVERTON, Ore. – Beekeeper George Hansen just got some good news: The bee hives he rents to a radish seed farm in Oregon’s Willamette Valley are healthy and full of honey. He shakes one of the combs and a sheet of nectar pours out.
“That’s all stuff they collected today," he said. "That’s pretty good. Makes the beekeeper feel pretty good.”
Hansen’s commercial beekeeping company leases 5,000 honeybee hives to all kinds of farms around the region. These professional honeybees have high risk jobs. They're trucked long distances to pollinate monoculture crops that offer limited nutrition, and they're often exposed to pesticides. All of the above makes them more vulnerable to pests and diseases that can wipe them out.
“They’re being exposed to agricultural chemicals just constantly, and it’s a lot harder to keep bees healthy under those circumstances,” Hansen said. "You put our pests and pathogens together with our chemical inputs in the environment, and the three things are working together against the honeybees."
Across the country, beekeepers have reported losing 30 percent of their colonies on average since 2006. Some attribute the declines to the use of certain pesticides — especially after chemical applications killed thousands of bees in Oregon.
But researchers say they're still trying to determine how much of the nation’s bee problem stems from pesticide exposure.
Researcher Ramesh Sagili, an assistant professor of apiculture and head of the Oregon State University Honeybee Lab says many perils of daily life for honeybees — a lack of nutrition, new and voracious pests and diseases as well as exposure to pesticides — are all part of the problem.
The varroa mite in particular has been especially destructive, he says. The mites suck the bees' blood and transmit viruses, and they will kill the bees if not controlled.
“It’s a complex, multi-factorial problem,” Sagili said. “The consensus among researchers is that these six or seven stress factors are playing a perfect storm role and compromising the immune system of the bees.”
But the question remains: How much of a role are pesticides playing in that storm? And is it enough to justify banning certain pesticides?
Mace Vaughan, a project manager for the insect conservation group The Xerces Society, says it’s hard to ignore the fact that the rise in bee losses follows an increase in the use of a type of pesticide known as neonicotinoids – or neonics for short.
"They've become the most widely used insecticides in the world," he said. "Xerces has some pretty significant concerns about their use."
Vaughan says some research suggests low levels of neonics can disrupt a bee’s ability to navigate and forage for food. That may not kill the bees, but it could have what scientists call a sub-lethal effect that raises their risk of getting sick. Vaughan's group argues neonics should be banned until a new safety review can be completed.
“We don’t have a smoking gun, but we do have research paper after research paper that indicates that very low doses have these sub-lethal effects,” Vaughan said. "You take these cumulative effects, and you can really undermine the ability of a honeybee colony – or a bumblebee colony – to be able to grow and prosper."
But none of the research so far has convinced Scott Dahlman that saving bees requires banning pesticides. Dahlman is the director of Oregonians for Food and Shelter. He represents farmers and the companies that make their pesticides, and he says there's a reason neonics are so widely used.
"They are much safer for human health and the environment than the other alternatives we've used in the past," he said. "If you take away that tool, people are going to be forced to use other tools."
Dahlman says banning pesticides could also result in massive crop losses. And that shouldn't be necessary if farmers follow the labels and avoid spraying when bees are around. He says studies showing sub-lethal effects of pesticides only tested bees in a laboratory.
"That's not what happens in the field," he said. "I don't think there's enough out there to truly understand what's going on when it comes to possible sub-lethal effects. But it is a robust area of research, and we'll continue to watch that."
Sagili says scientists don’t know whether low levels of pesticide exposure could weaken bees enough to cause colony declines. Or what happens when multiple pesticides are combined in a hive.
Sagili is working with graduate student Stephanie Perreira on an experiment that could help answer those questions. They started with about 40 bee hives of equivalent size and health in a field near OSU in Corvallis, Oregon. They'll be feeding the bees pollen laced with one pesticide and one fungicide. Then, Perreira will run a series of tests to see what effect that has on the bees.
The experiment is designed to fill a gap in existing research. It’s testing realistic levels of pesticides on bees in the field.
“I would like to say that my hypothesis is that being exposed to these pesticides will decrease their immune abilities and increase rates of disease," Perreira said. "But there really isn’t a lot of data on that.”
Sagili says the results could shed some light on the sub-lethal effects of pesticides on bees, but they won't be out for at least a year.