Neonicotinoid seed treatments provide significant economic benefits in Mid-South soybean production, according to a 10-year study conducted by scientists from four universities. The results of the meta-analysis were published in the Journal of Economic Entomology.

Neonicotinoids, a widely adopted class of insecticides, face increased scrutiny from both environmental groups concerned about their impact on pollinators and regulators who question the economic advantage they provide. Neonicotinoids are currently being reviewed by the U.S. Environmental Protection Agency.

“Most scientists will agree that there are critical knowledge gaps concerning neonicotinoids and their impact on bees,” said Scott Stewart, integrated pest management coordinator with the University of Tennessee Institute of Agriculture (UTIA). “What we do know is that at-planting insecticides are vital to crop production, particularly in the Mid-South, where we see pressure from multiple pest species. This study shows neonicotinoid seed treatments provide a clear value to the soybean producers of our region.”

Researchers from Mississippi State University, UTIA, the University of Arkansas and Louisiana State University analyzed 170 trials over 10 years comparing soybean seed treated with neonicotinoid plus a fungicide and soybean seed treated only with a fungicide. The soybeans treated with neonicotinoid averaged a 2 bu.-per-acre yield advantage over soybeans treated with the fungicide only. The neonicotinoid seed treatment also resulted in a net return of $12 per acre over soybeans on which no insecticide seed treatment was used.

“While soybeans may not be as responsive to neonicotinoid seed treatments as corn or cotton, we’re still talking about a 3-5% yield advantage, which is significant,” Stewart said. “For many farmers who are operating on extremely tight margins, that 5% could be what keeps them in business.”

Soybeans are an economically significant crop in the Mid-South, with more than 9 million acres planted throughout the region in 2015. In Tennessee alone, soybean production contributed more than $1 billion in economic activity.

Neonicotinoids have been implicated as a cause of declining honeybee health. However, a field study led by Stewart — results of which were published in Environmental Science & Technology in 2014 — found that the contribution of neonicotinoid seed treatments to this phenomenon was relatively low. The study evaluated the potential exposure of pollinators to neonicotinoid insecticides used as seed treatments on corn, cotton and soybeans. The results showed that concentrations of the insecticides in the crops’ flowers, pollen and nectar were "well below defined levels of concern," and in soybean flowers, concentrations were “non-detectable.”

“Because neonicotinoid insecticides and pollinator health are hot topics, there is a spotlight on risks, without much consideration of benefits.” Stewart said. "Our previous research shows pollinators are not being exposed to the insecticides used on seed when they visit soybean flowers.”

The researchers will continue to evaluate both the economic benefits of neonicotinoid seed treatments as well as their impact on pollinator health.