Evaluating a saponin biological seed treatment on soybean disease and yield in Michigan and the challenges in biological seed treatment efficacy

Abstract

Biological products are often marketed as yield enhancing and as disease management solutions. Soybean sudden death syndrome (SDS; Fusarium virguliforme) and White mould (Sclerotinia sclerotiorum) are major threats to soybean production in Michigan and most major soybean producing regions of North America. SDS management strategies primarily rely on host resistance and targeted fungicidal seed treatments, while White mould management primarily relies upon variety resistance and foliar fungicide applications. Fungicide resistance in pathogen populations is a continual concern and there is interest among soybean stakeholders in integrating biologicals into disease management programmes. This study investigated the efficacy of Chenopodium quinoa saponin seed treatment ‘Heads Up’ in managing SDS and White mould in soybean, as well as its yield impacts across Michigan in 2022–2024, by applying two treatments: a standard commercial base seed treatment (base) and base + Heads Up (61.3% a.i.; 15 mL·cwt−1). These treatments were assessed in small plot trials in eight commercial soybean cultivars across 20 site-years and on-farm split plot trials in seven additional cultivars across eight site-years. No significant differences in soybean yield (p = 0.9), SDS root (p = 0.7), SDS foliar (p = 0.3) or White mould (p = 0.5) disease indices were detected. These findings provide practical insights for soybean producers and align with previous studies, highlighting the need for further research into the efficacy of biological products marketed for disease management.