Corn Seed Treatment and Potential Risks to Honey Bees

A recent news release from Purdue University indicated that, “Nearly every foraging honey bee in the state of Indiana will encounter neonicotinoids during corn planting season, and the common seed treatments produced no improvement in crop yield, according to a Purdue University study. (Click for a video abstract).

“Neonicotinoids, including clothianidin and thiamethoxam, are a class of insecticide commonly applied as a coating to corn and soybean seeds to protect them from early-season pests. Since the coatings are sticky, a talc or graphite powder is added to vacuum systems in planters to keep the seeds from clumping. Powder exhausted from the planter contains neonicotinoids.

“The United States is losing about one-third of its honeybee hives each year, a significant problem since the bees pollinate many crops used to feed people and livestock. Neonicotinoids, which are highly toxic to honeybees, are being scrutinized as a possible contributor to the losses.”

The news update noted that, “Christian Krupke, a professor of entomology, showed in 2012 that exhausted insecticides collected on flowers that border agricultural fields and were present in hives near those fields. Bees in those hives showed physical signs of insecticide poisoning, and dead bees tested positive for the neonicotinoids used as seed treatments of corn and soybeans.

“Now, Krupke, along with collaborators Jeff Holland at Purdue, Elizabeth Long at Ohio State University, and Brian Eitzer with the Connecticut Agricultural Experiment Station, have measured the drift of those neonicotinoids from fields and found that the insecticides can settle on flowers up to 100 meters from the edge of the planted fields, the farthest distance examined in the study. Their findings are published in the Journal of Applied Ecology.”

The Purdue update added that, “Mapping Indiana‚Äôs corn acreage, as well as the areas that may receive drift, the authors say that 42 percent of the state is exposed to neonicotinoids during crop planting. Looking at public data on the location of apiaries and projecting the range that honey bees forage, they found that 94 percent of bees could fly through areas that contain lethal doses of the insecticides during the period when corn is planted.”

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