2018 Corn Product Yield Response to Fungicide Application - DEKALB®

Trial Objective

  • 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 trial was conducted to evaluate the yield response of DEKALB® brand blend corn products to a fungicide applied at the R1 (silking) growth stage.

Research Site Details

  • Each seed product had two treatments:
    • 1) No fungicide
    • 2) Delaro® 325 SC Fungicide applied at 10 fl oz/acre on July 3, 2018 at the R1 (silking) growth stage
  • Disease incidence was as follows:
    • gray leaf spot – low to moderate
    • southern corn rust – low

Understanding the Results


  • For five of the eight products, higher yields were observed when treated with the fungicide.
  • In this trial, the yield difference observed with the application of fungicide ranged from -8 to +53 bu/acre. The positive yield increases are likely due to the inhibition of gray leaf spot and/or southern rust.
  • The highest yield responses to the fungicide treatment were observed with DKC60-88RIB, DKC58-35RIB, and DKC61-98RIB brand blends, suggesting that these products are more likely to benefit from a fungicide application under moderate to high disease pressure.
  • The average yield response to the fungicide application for the 105 to 112 RM products was 33.8 bu/acre.
  • The average yield response to the fungicide application for the 113 to 120 RM products was a negative 2.0 bu/acre.

What Does This Mean for Your Farm?

  • Fungicides can protect yield potential when applied correctly.
  • The benefits of a foliar fungicide application at the appropriate growth stage may have more impact when applied to moderate to susceptible (disease ratings) products under high disease pressure.
  • Scouting plans should be in place prior to tasseling for fields with susceptible genetics, that are continuously corn-oncorn, 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 apply a fungicide.
  • Farmers can further minimize the risk of disease-induced yield loss by selecting a resistant to moderately-resistant product when planting in disease-prone regions.