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Corn+Soybean Digest

Bee Threat at Planting

Watch seed treatment drift that poses springtime danger to pollinators.


Colony Collapse Disorder (CCD) continues to keep honeybees in the headlines as beekeepers lose on average one-third of their hives annually. But CCD is not the only problem that affects bees. Bee populations in general, including bumblebees and ground-nesting solitary bees, are declining.

Purdue University research since 2010 identified one possible cause – dust from corn seed treatments. Researchers continue to examine the role of neonicotinoid pesticides in springtime bee deaths. Neonicotinoids such as clothianidin (Poncho) and thiamethoxam (Cruiser) are widely used as corn seed treatments.

Purdue Entomologist Christian Krupke has looked at why Indiana had persistent reports of bee kills at corn-planting time. “These were not abandoned hives like CCD, so we could test the dead bees to see what they had come in contact with.”

Talc dust spreads

Krupke’s lab sent samples to Brian Eitzer, Connecticut Ag Experiment Station, who screened for more than 100 pesticides and found neonicotinoids. That led Krupke to examine soils, dandelions; everything that a honeybee living near cornfields could come in contact with.

“We found neonicotinoids everywhere we looked…in the pollen, in the hives, in field soil where they had not been used for two full seasons. The largest single potential exposure is the talc dust that comes off of planters. It’s a form of pesticide drift that hadn’t been considered but could be important early in the season,” Krupke reports.

The challenge for growers is to minimize the impact of neonicotinoids on pollinators, he says. “We’re trying to nail down the physics of how this material moves in the environment so we can move on to solutions. Growers, manufacturers and researchers are looking for ways to lubricate seeds that don’t involve talc dust.”

One response he does not expect to see is a ban on neonicotinoids. “They are used so extensively that a ban would be a mammoth task affecting so many cropping systems and crops. The EPA is being very cautious. I don’t believe they will act unless they have a smoking gun.”

In the meantime, farmers can help by taking the same care with treated seed as they do when spraying, according to Iain Kelly, technical manager, Bayer Bee Care program and leader of CropLife America’s Pollinator Issue Management team.

“We think farmers are doing a pretty good job, but it doesn’t hurt to remind them of good management practices like making sure they clean [planting] equipment well away from sensitive areas and deal with any residue according to label recommendations,” he notes.

Bee friendly during planting

  • Follow manufacturer recommendations for using talc or graphite and avoid using more than recommended.
  • Avoid adding excess dust from the bottom of the seed container to the planter.
  • Minimize off-site dust movement from treated seeds.
  • Stay alert to wind speed and direction, particularly near flowering crops which could attract pollinators.
  • Incorporate treated seed into the soil at proper depths, especially at row ends and field corners.
  • Clean planters and seed boxes away from environmentally sensitive areas that might attract pollinators.

For more tips on good seed treatment management, download a pdf.

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