Application of a fungicide has been shown to protect corn plants from foliar diseases and improve overall plant appearance, which may lead to increased grain yield.
Yield increases observed from the application of fungicide in the absence of foliar disease greatly depends on the corn product, as individual products respond differently to fungicide application. While fungicide is often used as a high-yield management strategy, it can also be used to protect the yield of products with poor plant and stalk strength ratings.
The objective of this study was to evaluate the impact fungicide application has on corn yield and good plant appearance.
Research Site Details
Thirteen DEKALB® brand corn products were tested, broken out into two different sets based on relative maturity (RM). The northern set included products that ranged from 97 to 111 RM and the southern set included products that ranged from 108 to 115 RM.
Marble Rock and Storm Lake were the north locations; Victor and Atlantic were the south locations. Due to its central location, both the northern and southern sets were located at Huxley, giving each product three locations.
Plots were planted as strip trials at four of the locations, with Huxley being arranged as a small-plot trial.
The locations served as replications.
Each site was sprayed with USF0411 fungicide at 8 oz/acre with a ground sprayer at the R1 corn growth stage.
Foliar disease and stalk quality ratings were taken at R4 growth stage and grain moisture and yield were collected at harvest.
UNDERSTANDING THE RESULTS
All research locations had some levels of corn disease incidence, with disease level averaging from low to moderate across locations. Gray leaf spot, Northern Corn Leaf Blight and Anthracnose stalk rot were the most predominant diseases across locations. Disease incidence was observed in both fungicide-treated and untreated plots, and there were no differences in disease incidence and severity between treatments.
Late season stay green and intactness scores were taken but there were no differences observed between the fungicide-treated and untreated plots.
Across all corn products, spraying fungicide resulted in an average of 12-13 bu/acre advantage vs. the unsprayed treatment (Figures 2 and 3). For this study, a 7 bu/acre response was considered a profitable response ($24/acre cost for fungicide application with $3.50 corn).
Fungicide application had a small effect on grain moisture, with an overall average of 0.6% difference in moisture between the sprayed and unsprayed treatments. The total difference in moisture for the southern set was 0.4% vs. 0.7% for the northern set (Table 1).
Three products; DKC58-34RIB, DKC59-81RIB and DKC61-98RIB were planted in both north and south locations to understand product response to fungicide at different geographies. When planted in the appropriate geography for their relative maturities (northern half of Iowa), DKC58-34RIB and DKC59-81RIB provided economic returns to fungicide application (Fig. 1). However, they did not provide economic response to fungicide when planted in the south (Fig. 2). DKC61-98RIB did not provide economic gains to fungicide application in the north but a good gain in the south where it is well suited for its relative maturity (Figures 1 and 2).
The 2019 growing season saw a range of moisture and temperature extremes across the state of Iowa. Generally, the research sites experienced wet planting conditions, a hot and dry July, and a wet late summer/harvest season. This led to some levels of stalk strength and plant appearance issues due to excess moisture, nutrient shortages, and prolonged harvest conditions.
Such conditions may explain why fungicide was profitable across nearly all products tested in 2019. While plant appearance was notably improved by fungicide use, we did not observe dramatic differences in stalk strength between sprayed and unsprayed products. This could be due, in part, to improvements in our corn germplasm to inherently tolerate some of these adverse growing conditions.
The results of this study suggest that fungicide application could promote a healthier upper canopy that would lead to increased photosynthetic activity and better plant stress tolerance, which might result in increased corn yields. To gain the full benefits of a fungicide, the right corn product should be selected for the growing region.
Going forward, protecting yield and improving overall plant appearance with the use of a fungicide may be a management decision worth considering on your operation.