Fungicide seed treatment impact on soybean stand and yield across planting dates and maturity groups in North Carolina

Producers across the state of North Carolina are planting soybean at earlier planting dates as a mechanism to increase yield, and as a result, questions arise regarding whether fungicide seed treatments are needed at earlier planting dates to protect soybean stand and yield. Experiments were conducted from 2019 to 2020 at four environments across North Carolina that were selected to represent a range of geographies and growing conditions commonly encountered in North Carolina soybean production. Planting dates evaluated included early April, mid- to late April, mid-May, and mid-June. Maturity groups evaluated included III, IV, and V. The seed treatments included in this study represent a range of the commercially available fungicide seed treatments and fluctuated between 2019 and 2020 but were compared to a nontreated control in each environment. Fungicide seed treatment impact on soybean stand was variable across environments, with stand protection from using treated seed in one environment of 12,146 plants ha⁻¹ at the earliest planting date (early April). Soybean maturity group also impacted the value of a fungicide seed treatment, which is likely a result of differing varietal resistance packages to seedling diseases among the soybean maturity groups used in this study. Fungicide seed treatments provided considerable yield protection at planting dates in mid-May and earlier. Results across these environments emphasize the variability in which fungicide seed treatment can protect soybean stand and yield across planting dates and environments, and producers should consider planting date and environmental conditions when making decisions about this input.