Research Update: Foliar Fungicide Impact on NC Soybean Yield and Seed Quality

By Rachel Vann

A recent analysis of 877 entries into the NC Soybean Yield Contest indicated that foliar fungicide use was a strong predictor of high soybean yield in this state. Small-plot research conducted on this topic by the NC State Soybean Extension Program several years ago found that on average single MOA foliar fungicides protected yield by 1-2 bu/A and multi-MOA foliar fungicides protected yield by 2-3 bu/A. Additionally, a recent meta-analysis from the North Central United States found that the yield increase from foliar fungicide use was greater as planting date was delayed and at lower latitudes.

The NC State Soybean Extension Program evaluated a variety of foliar fungicides across a diversity of production environments in 2021 to capture environmental and yield variability. Priaxor was evaluated alone without the addition of another foliar fungicide. A report from that research is available here NC State FYE 2021

Disease pressure across environments: We conducted this trial in four diverse NC environments which resulted in variability in disease pressure across these environments. At the Edgecombe County environment there was very heavy frogeye leaf spot pressure. At the Union County environment there was very uniform late season Cercospora pressure. At the Washington County environment there was low to moderate disease pressure from both frogeye leaf spot and Cercospora. At the Yadkin County environment there was no visual disease pressure.

Foliar fungicide impact on soybean yield: As you would expect with a diversity of disease pressure across these research environments, there was variable impact on yield from the use of foliar fungicides. Foliar fungicides provided considerable yield protection at the Edgecombe County environment where there was heavy disease pressure and trended towards doing so at the Washington County environment. When you combined over environments, several multi-mode of action foliar fungicides provided significant yield protection compared to the non-treated control.

Thank you to the following Agents who hosted these trials: Andrew Baucom (Union Co), MiKayla Graham (Union Co), Tim Hambrick (Yadkin Co), and Jalynne Waters (Washington Co). Thank you to the following growers who hosted these trials: Greg Moxley, Manning Bros. Farms, and Cox & Watson AG. We also appreciate the Upper Coastal Plain Research Station for hosting this trial in 2021.