Soybean Seed Yield Response to Multiple Seed Treatment Components Across Diverse Environments.

Soybean [Glycine max (L.) Merr.] seed treatment adoption has increased dramatically over the past decade in addition to the number of pesticide components within commercially available seed treatments.  The study objectives were to evaluate the effects of multiple seed treatments and their individual pesticide components (fungicide, insecticide, and/or nematicide) on soybean plant stand and seed yield across diverse environments.  Trials were conducted at ten Wisconsin locations during the 2011-2013 growing season.  Soybean seed treatments containing fungicide + insecticide + nematicide increased plant stands over the untreated control (UTC), fungicide only, and fungicide + insecticide seed treatments by an average of 10%, 9%, and 5.5%, respectively.  During 2013, yield was increased by the fungicide only seed treatment pyraclostrobin + metalaxyl + fluxapyroxad; however, across all environments, no consistent yield increase was shown for fungicide only seed treatments.  Fungicide + insecticide seed treatments increased yield over fungicide only seed treatments by 55 and 76 kg ha^-1 during 2011-2012 and 2013, respectively, and were similar to fungicide + insecticide + nematicide seed treatments.  However, fungicide + insecticide and fungicide + insecticide + nematicide seed treatments only increased yield over the UTC in 2013.   These results suggest that though fungicide + insecticide and fungicide + insecticide + nematicide seed treatments consistently increased plant stand, yield increases were variable and contingent upon unpredictable factors. Therefore, producers will need to weigh potential yield gains with biological (resistance management) and economic (ROI and risk mitigation) concerns before implementing seed treatment practices at the whole farm level.