Treated Seeds May Contribute to Honeybee Losses

May 21, 2014

Nathan Anderson stops his red pick-up truck alongside a cornfield on his farm near Cherokee, Iowa. The young farmer pulls on a heavy brown hoodie, thick long, sturdy yellow gloves and a beekeeper’s hat with a screened veil. He approaches a pair of hives sitting on the edge of a field recently planted with corn.

“I need to close the pollen traps on these bees,” he said. As bees buzz around their hive, Anderson reaches out and moves a flap on the plastic trap attached to the hive. “That little yellow door on the front, that’s the pollen door. And there’s kind of like a drawer underneath it and that’s where, as the bees are forced through those small openings, it brushes some of the pollen off and it falls down into that drawer.”

Anderson is not a beekeeper. But he’s agreed to help researchers study bees on cropland because honeybee colonies have been dying off at alarming rates in recent years and some people are wondering if part of the problem in the Midwest is the vast seas of corn and soybeans.  Specifically, Iowa State University researcher Mary Harris wants to determine whether neonicotinoids—insecticides found in the coatings on most corn and soybean seeds—are responsible for the fragility of some hives. Harris says when corn is planted, dust vented from the high-tech planters may include residue from the seed coating. Harris has found that the pollen bees collect during planting can contain some of the toxins.

“The highest concentrations were detected in the pollen that was collected the week of planting,” she said, and then the levels decrease.

Neonicotinoids kill certain grubs, aphids and beetles; not bees. But Harris says nonlethal exposure still hurts the bees.

“They’re not as able to carry out the various functions that are going to set the hive up to have a really healthy, successful season,” she said. That may contribute to higher over-winter losses.

Coated seeds are easy for farmers to use and, Harris said, they can be an important part of an integrated pest management system. Some home gardening products also contain neonicotindoids.

“Some of the aspects that make these such good chemicals may also be creating some environmental problems,” Harris said.

Farmer Bob Lynch in Gilmore City, Iowa is open to hearing how he might help solve the problem, if it turns out his planting method is contaminating pollen.

“I don’t think I’m the total cause of this,” he said. “[But] if we have to change the way our planters vent, that we can possibly do.”

It wouldn’t be easy. But the bee situation is dire. Over the past eight years, nearly a third of all bees nationwide died annually. Beekeepers say some losses are routine, but the recent levels are jeopardizing the entire population.

The seed treatments that Harris is studying are ubiquitous. Nearly all corn seed sold in this country has an insecticide treatment. At Plunkett Seeds in Maxwell, Iowa, Gary Plunkett sends plain yellowish-beige soybean seeds into a treatment chamber.  He adds a dull pink liquid and sets the machine in motion. The seeds bounce and dance in a flow of air that sprays on the treatment.

Plunkett can sell soybean seeds with or without the coating—he puts it on to order. But he says most of his customers want it. All of his corn seed comes to him already treated. Farmers have used insecticides on their crops for decades, so Plunkett is skeptical that these seed coatings are now killing bees.

“It’s an easy escape for ag,” he said, “just like the carryover of chemicals and stuff. It’s easy to blame the farmer.”

Scapegoating or not, the European Union has put a two-year ban on certain neonicotinoids. And Dupont Pioneer is selling corn and soybean seeds without the toxins… in Canada.

But Iowa State entomologist Amy Toth says even if neonicotinoids completely disappeared, bees would still be in trouble.

“The corn dust could be having an impact on hives in some situations,” Toth said. “It’s not explaining the whole collapse of the beekeeping industry.”

Figuring out the combination of factors that’s killing bees, Toth says, is important to preserving the way we all eat. Corn and soybean crops don’t rely on bees and other pollinators. But most fruits, nuts and vegetables do.

“Without bees the cost of our food would go up dramatically. We wouldn’t starve to death, without bees,” Toth said, “but we would have a lot less variety in our diet.”

There is some good news for pollinators. USDA has made $3 million available to help farmers create bee habitat on conservation land in five Midwestern states. Cover crops, which have been re-gaining popularity for a variety reasons in the Corn Belt, can provide quality food for pollinators.  And bee deaths this past winter were lower than they have been in years—but not yet low enough to reverse the trend.

“There’s not going to be a single silver bullet that’s going to fix everything,” Toth said. “I wish there was.”