Neonicotinoids are the most widely used insecticides worldwide and are typically deployed as seed treatments (hereafter NST) in many grain and oilseed crops, including soybeans. However, there is a surprising dearth of information regarding NST effectiveness in increasing soybean seed yield, and most published data suggest weak, or inconsistent yield benefit. The US is the key soybean-producing nation worldwide and this work includes soybean yield data from 194 randomized and replicated field studies conducted specifically to evaluate the effect of NSTs on soybean seed yield at sites within 14 states from 2006 through 2017. Here we show that across the principal soybean-growing region of the country, there are negligible and management-specific yield benefits attributed to NSTs. Across the entire region, the maximum observed yield benefits due to fungicide (FST = fungicide seed treatment) + neonicotinoid use (FST + NST) reached 0.13 Mg/ha. Across the entire region, combinations of management practices affected the effectiveness of FST + NST to increase yield but benefits were minimal ranging between 0.01 to 0.22 Mg/ha. Despite widespread use, this practice appears to have little benefit for most of soybean producers; across the entire region, a partial economic analysis further showed inconsistent evidence of a break-even cost of FST or FST + NST. These results demonstrate that the current widespread prophylactic use of NST in the key soybean-producing areas of the US should be re-evaluated by producers and regulators alike.
Bibliographical noteFunding Information:
S.M. synthesized the data base, contributed to idea development, carried out the statistical analysis, and wrote the paper. S.P.C. conceived the idea, contributed to data aggregation, reviewed results, and provided revisions to improve the manuscript. C.H.K. contributed to manuscript write-up, contributed data, and reviewed results. P.D.E. contributed to the statistical analysis and idea development, reviewed results and commented on the manuscript. P.D.E was supported under USDA National Institute of Food and Federal Appropriations under Project PEN04660 and Accession number 1016474. A.V. contributed to introduction material and data. The rest co-authors contributed data, reviewed results, and provided revisions to improve the manuscript.
© 2019, The Author(s).