Corn Seed Product Response to Fungicide Application - DEKALB® - CO KS MO



  • The impact of a fungicide application on corn yield can be influenced by several factors including seed product disease tolerance and existing disease pressure.
  • This study was established to determine the yield response of fungicide application on six DEKALB® corn seed products.


  • Evaluate corn seed products yield response to fungicide applied at R1 (silking) growth stage.
  • The objective of the trial was to evaluate the visual response of corn products planted in neutral pH (5.8 to 7.5) soils and high pH (7.6+) soil conditions. Improved product characterization allows for better product placement to help maximize yield potential.
Location Soil Previous Crop Tillage Type Planting Date Harvest Date Potential Yield/Acre Planting Rate/Acre
Camden Point, MO Silt loam Corn Minimum Tillage 04/17/2017 09/27/2017 200 bu 34,000 seeds/acre

  • Each seed product had two treatments: 1) No fungicide; 2) Stratego® YLD Fungicide applied at 5 fl oz/acre on July 17, 2017 at R1 (silking) growth stage.
  • Disease incidence was as follows: gray leaf spot - moderate; southern corn rust - low; crown rot - observed to be present.


Figure 1. Corn seed product response to fungicide application at R1 (silking) growth stage.


  • The application of Stratego® YLD Fungicide increased yield in five of the six brand blend products.
  • In previous Monsanto inoculated disease trials, under high disease pressure, all brand blend products in the trial were rated 4 or 5 on a scale of 1 to 9 (with 1 being resistant and 9 being susceptible) to gray leaf spot (GLS).
  • In this trial, the yield increase observed on five seed products with the application of Stratego® YLD Fungicide ranged from 7.1 to 27.1 bu/acre and is likely the result of the inhibition of GLS and/or southern rust development.
  • In comparison, DKC 65-94RIB brand blend, saw no yield advantage from fungicide application. This seed product’s host resistance presumably provided adequate protection for the severity of GLS observed in Camden Point, Missouri during 2017. Therefore, the application of Stratego® YLD Fungicide or application timing did not contribute to disease control or impact yield potential for this seed product.
  • Seed products rated as moderate to GLS exhibited a more consistent yield response to Stratego® YLD Fungicide application compared to seed products rated as moderately resistant to GLS.
  • No significant differences in grain moisture content were observed across treatments.


  • Fungicides can protect yield when applied correctly.
  • The benefits of a fungicide treatment at the appropriate growth stage may have more impact when applied to moderate to susceptible (disease ratings) seed products under high disease pressure conditions.
  • Scouting plans should be in place prior to tasseling for fields with susceptible genetics, that are continuously corn-on-corn, or have a history of disease.
  • Yield potential, corn growth stage, disease risk, cost of fungicide, and corn commodity price should all be considered when deciding whether to spray a fungicide.
  • Farmers can further minimize the risk of disease-induced yield loss by selecting a resistant to moderately-resistant seed product when planting in disease-prone regions.
  • The data is a result of a single, non-replicated study conducted in Camden Point, Missouri and is intended to represent the seed products’ response under 2017 conditions for this region. Results may vary depending on disease presence, environmental conditions, and other factors.


1 Rees, J.M. and Jackson, T.A. 2008. Gray leaf spot of corn. NebGuide G1902. University of Nebraska-Lincoln Extension. 2 Nielsen, R.L. 2017. Stress during grain fill: A harbinger of stalk health problems. Purdue University. Web sources verified 11/24/17. 171016105359

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