As soybean (Glycine max) production continues to expand in the U.S. and Canada, so do pathogens and pests which directly threaten soybean yield potential and economic returns for farmers. One such pathogen is the soybean cyst nematode (SCN; Heterodera glycines). SCN has traditionally been managed using SCN-resistant cultivars and rotation with non-host crops, but the interaction of SCN with sudden death syndrome (SDS; caused by Fusarium virguliforme) in the field makes management more difficult. Nematode-protectant seed treatments have become options for SCN and SDS management. The objectives of this study were to evaluate nematode-protectant seed treatments for their effects on: (i) early and full season SCN reproduction, (ii) foliar symptoms and root-rot caused by SDS, and (iii) soybean yield across environments accounting for the above factors. Using a standard protocol, field trials were implemented in 13 U.S. States and 1 Canadian Province from 2019 to 2021 constituting 51 site-years. Six nematode-protectant seed treatment products were compared to a fungicide + insecticide base treatment and a non-treated check. Initial (at soybean planting) and final (at soybean harvest) SCN egg populations were enumerated and SCN females were extracted from roots and counted at 30 to 35 days post-planting. Foliar disease index (FDX) and root rot caused by the SDS pathogen were evaluated, and yield data were collected for each plot. No seed treatment offered significant nematode control versus the non-treated check for in-season and full season nematode response, no matter the initial SCN population or FDX level. Of all treatments, ILEVO (fluopyram) and Saltro (pydiflumetofen) provided more consistent increases in yield over the non-treated check in a broader range of SCN environments, even when FDX level was high.
Keywords: seed treatments; soybean; soybean cyst nematode; sudden death syndrome.