Citation:

Purucker, Tom, E Henry Lee, T. Purucker, R. Johnson, C. Lin, D. Sponsler, R. Richardson, H. Watters, D. Glinski, Matt Henderson, AND J. Minucci. Honey bees and neonicotinoid-treated corn seed: contamination, exposure, and effects. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 40(4):1212-1221, (2021). https://doi.org/10.1002/etc.4957

Impact/Purpose:

Pesticide exposure and mortality of free-flying bees are influenced by complex factors that are difficult to measure in the field. The level of exposure depends on the spatial and temporal intersection of foraging bees and active corn planting, both of which are influenced by weather and can be highly variable across sites.

Description:

Most corn (Zea mays) seeds planted in the United States in recent years are coated with a seed treatment containing neonicotinoid insecticides. Abrasion of the seed coating generates insecticide¿laden planter dust that disperses through the landscape during corn planting and has resulted in many “bee¿kill” incidents in North America and Europe. We investigated the linkage between corn planting and honey bee colony success in a region dominated by corn agriculture. Over 3 yr we consistently observed an increased presence of corn seed treatment insecticides in bee¿collected pollen and elevated worker bee mortality during corn planting. Residues of seed treatment neonicotinoids, clothianidin and thiamethoxam, detected in pollen positively correlated with cornfield area surrounding the apiaries. Elevated worker mortality was also observed in experimental colonies fed field¿collected pollen containing known concentrations of corn seed treatment insecticides. We monitored colony growth throughout the subsequent year in 2015 and found that colonies exposed to higher insecticide concentrations exhibited slower population growth during the month of corn planting but demonstrated more rapid growth in the month following, though this difference may be related to forage availability. Exposure to seed treatment neonicotinoids during corn planting has clear short¿term detrimental effects on honey bee colonies and may affect the viability of beekeeping operations that are dependent on maximizing colony size in the springtime.

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