May 19, 2019
- The impact of a fungicide application on soybean yield can be influenced by several factors including soybean product disease tolerance and existing disease pressure.
- This study was conducted to evaluate the yield response of Asgrow® brand soybean products to fungicide applied at R2 (full bloom) to R3 (beginning pod) growth stages.
Research Site Details
- Eight Asgrow® brand soybean products with relative maturity ranging from 3.3 to 4.3 were planted in a split strip plot and each soybean product was either treated with a foliar application of 10 fl oz/acre of Delaro® 325 SC fungicide at R2 (full bloom) to R3 (beginning pod) growth stage or was untreated.
- Individual treatment areas were four 30-inch rows wide and 300 feet long.
- Some soybean diseases (bacterial leaf blight, Sclerotinia stem rot, and frogeye leaf spot) were observed at low levels but no soybean disease was prevalent at an economic threshold.
Understanding the Results
- A fungicide application increased the average yield of seven of the eight Asgrow® brand soybean products compared to the untreated control (Figure 1).
- Although heavy disease pressure was not visibly observed when combined overall products there was an average of a 3.3 bu/acre yield increase for soybean treated with a fungicide compared to the untreated control (Figure 1).
- The yield response to a fungicide application was variable, ranging from a positive 5 bu/acre to negative 1 bu/acre (Figure 1).
- No significant difference in grain moisture contents was observed across the treatments.
- Based on this demonstration study, applying a fungicide at the R2 to R3 growth stage may provide a potential yield increase even with mild disease pressure.
What Does This Mean for Your Farm?
- Foliar fungicides are a valuable soybean disease management tool.
- To determine if a fungicide application is warranted, consider yield potential, soybean growth stage, potential for additional development of disease symptoms, fungicide application cost, and the commodity price of soybean grain.
- In this 2018 demonstration, the fungicide application at the R2 to R3 growth stage increased average overall yield by 3.3 bu/acre over untreated soybeans.
- Similar trials will be repeated in the 2019 growing season.
1Heatherly, L.G. January 2016. Management decisions based on planting date. Mississippi Soybean Promotion Board. http://www.mssoy.org