Testing Corn Product Response to a Fungicide in Iowa

Trial Overview

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  • Corn yield potential can vary from year to year because of environmental conditions such as rainfall and temperature, which can influence disease development, and how these conditions interact with individual corn products.
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Research Objective

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  • To evaluate the effect of fungicide application(s) on corn yield potential, research trials were established at five Iowa locations: Storm Lake, Manchester, Atlantic, Victor, and Huxley.
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Location
Soil Type
Previous Crop
Tillage Type
Planting Date
Harvest Date
Potential Yield
Planting Rate
Storm Lake, Iowa
Silty clay loam
Corn
Conventional
05/06/2016
10/14/2016
225 bu/acre
35,000 seeds/acre
Manchester, Iowa
Loam
Corn
Minimum
04/25/2016
10/04/2016
220 bu/acre
34,000 seeds/acre
Victor, Iowa
Silty clay loam
Corn
Conventional
04/22/2016
09/29/2016
220 bu/acre
34,000 seeds/acre
Atlantic, Iowa
Silty clay loam
Corn
Conventional
04/15/2016
10/01/2016
230 bu/acre
35,000 seeds/acre
Huxley, Iowa
Clay loam
Soybean
Conventional
04/25/2016
10/18/2016
220 bu/acre
35,000 seeds/acre
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Site Notes:

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Trial Design: Randomized, complete block split-plot design; untreated block and treated block, fungicide treatments were not replicated at a location; 3 reps of products within fungicide treatments; 4, 30-inch rows with a length of 45 feet; two middle rows harvested for yield comparisons; corn products were representative for the locations; products separated into North sets and South sets; 10 DEKALB® brand blend products and 16 other corn products. Fungicide Application: Headline AMP® Fungicide applied to respective plots at 10.5 oz/acre at the VT-R1 growth stage. Fungicide application dates: Huxley, July 11, 2016; Atlantic, July 13, 2016; Storm Lake, July 14, 2016; Victor, July 15, 2016; Manchester, July 21, 2016.
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Understanding the Results

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Figure 1A. Effects of a fungicide application on the grain yield of five
 
13;10;DEKALB® brand blend products at three Iowa North locations in 2016.
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  •  
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  • Though the goal of this trial was to determine the effectiveness of a fungicide application to different corn products, there was very minimal disease incidence at the time of application at all locations; therefore, the following results should be viewed with the understanding that respective yield increases may have been a result of the fungicide application and/or other agronomic factors. Additional information should be reviewed to determine if a fungicide application is warranted. The results presented (except for Figure 3) are only for the DEKALB® brand blend products within the trial.
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  • North sets (Figure 1A): DEKALB® DKC57-97RIB brand blend this year displayed a positive response at the three Iowa North locations; DEKALB® DKC58-06RIB brand blend this year displayed a positive response at the Manchester, Iowa  location; the Storm Lake, Iowa location this year displayed the largest response among the five products except for DEKALB® DKC58-06RIB and DKC59-50RIB brand blend products, which had their largest response at the Manchester, Iowa location.
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  • South sets (Figure 1B): The five DEKALB® brand blend products for this year displayed positive responses at the three Iowa South locations except for the zero response for DEKALB® DKC61-54RIB brand blend at the Huxley, Iowa location; DEKALB® DKC61-54RIB and DKC62-20RIB brand blend products for this year displayed their largest response at the Victor, Iowa location; DEKALB® DKC63-60RIB and DKC64-34RIB brand blend products for this year displayed their largest response at the Atlantic, Iowa location; DEKALB® DKC62-77RIB brand blend for this year displayed its largest response at the Iowa locations of Huxley and Victor.
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  • In general, the South set or late RM products this year, under these conditions and applications, displayed larger yield responses to fungicide applications than the North set or early RM products. Product placement could be more critical in the North sets than in the South sets, except for DEKALB® DKC57-97RIB brand blend.
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  • At the five Iowa locations this year, the DEKALB® brand blend products, except DEKALB® DKC58-06RIB brand blend, responded positively to a fungicide application (Figure 2). Yield gains ranged from a minimum of 3 bu/acre for DEKALB® DKC59-50RIB brand blend to a high of 33 bu/acre for  DEKALB® DKC62-20RIB brand blend. Grain moisture content percentages were slightly higher for the fungicide treated products except for DEKALB® DKC58- 06RIB brand blend. In both the North and South sets, the highest gain in moisture content correlated with the highest gain in yield and the lowest moisture content with the lowest yields.
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What Does This Mean for Your Farm

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  • 1) A fungicide application has the potential to help maintain product yield potential; however, the magnitude of the response depends on the location, year, and the corn product. 2) Depending on the corn product, fungicides may affect the rate of dry down, which can affect harvest date. Therefore, growers should scout for stalk diseases, integrity, and standability. 3) There was a large location response to the application of a fungicide (Figure 3). Therefore, consideration should be given to the economic value of fungicide applications as it relates to yield potential and grain drying cost.  At the current commodity price of corn and the cost of a fungicide application, an increase of about 8 to 10 bu/acre is required to justify a fungicide application.
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