Effects of Fungicide and Planting Date on Soybean Yield

Trial Overview

  • In many cases, a foliar fungicide application can protect soybean plant health and help maintain the yield potential of the product. 

Research Objective

  • The objective of this trial is to help determine the effect of a foliar fungicide application on soybean yield potential with respect to planting date.
Soil Type
Previous Crop
Tillage Type
Planting Date
Harvest Date
Potential Yield
Planting Rate
Monmouth, IL
Silt Loam
70 bu/acre
130,000 seeds/acre
Monmouth, IL
Silt Loam
70 bu/acre
130,000 seeds/acre

Site Notes:

The trial used a 3.6 RM soybean product with Roundup Ready 2 Xtend® technology.The trial was replicated twice.Two planting dates:
        - April 25, 2017
        - May 30, 2017
Foliar fungicide application dates depended on the plants reaching the R3 growth stage:
        - April 25 planting date was sprayed on July 20, 2017
        - May 30 planting date was sprayed on August 7, 2017



Understanding the Results

Figure 1. Yield response to a fungicide application based on planting period (2017 - Monsanto Learning Center, Monmouth, IL)
  • A fungicide application showed little effect on soybean yield in 2017 (Figure 1).
  • The early planting led to a substantial advantage over the late planting in 2017 (Figure 1).
  • A very low disease incidence occurred in 2017 because of cooler and drier than normal conditions.
  • In years such as 2016, when disease incidence was higher, a fungicide application can do more to protect yield potential (Figure 2).

What Does This Mean for Your Farm

  • The benefit of fungicide applications will vary from year to year.
  • Scouting regularly is the recommended way to determine if a fungicide application can be beneficial.
  • Over the majority of years, early-planted soybean crops tend to out-perform later-planted crops fairly consistently.
  • Early planting assumes that the soil and weather conditions are suitable for seedbed preparation and seed germination.
  • Individual fungicide application results may vary based on disease presence. Consult your local seed provider for recommendations.