Predictive Models Show Early Development of Disease in our 2020 Crop

Jul 01, 2020

Our partners at Syngenta and DTN have provided us with predictive modeling maps on the most prevalent corn diseases; Grey Leaf Spot and Northern Corn Leaf Blight.

This modeling shows that growers across the region can expect to some amount of disease pressure from NCLB and Gray Leaf Spot.

A wide view of disease outlook and regional trends can help make the right choice in the decision to apply fungicide. However, a majority of the time a field carries its own unique history, environment, and hybrid. In order to make the decision that truly works for your field, there needs to be an understanding of it's hybrid, environment, and the specific disease. 

The Disease Triangle

The Disease Triangle is a visualization of the three factors the environment, a host, and an infectious agent. The severity of disease depends on the favorable level of each factor marked by a fill towards the corner of the appropriate component. 


The scenario on the bottom left has a variety with lower disease tolerance, weather that’s vulnerable for pathogens which results in a higher chance for disease. The scenario on the right has conditions that is not favorable for disease.


Below are three high stress diseases that can be managed with a fungicide application.

Northern Corn Leaf Blight

Northern-Corn-Leaf-Blight-(1).jpgCaused by the fungus Exserohilum turcicum, early symptoms of Northern Corn Leaf Blight consist of long and narrow tan lesions that form parallel to the leaf margin.

Preventative measures include selecting resistant hybrids, corn rotation and tillage. Foliar fungicides may be applied as a risk-management tool early in the growing season with additional fungicide applications if the disease is identified in the field further into the growing season.



Gray Leaf Spot

Caused by the fungus Cercospora zeae-maydis,the disease has increased in importance in Indiana since the mid-90s, Hybrid susceptibility and weather strongly influence disease development, which is why gray leaf spot can be locally severe, but not cause widespread damage throughout the state.

Gray leaf spot can impact yield given favorable conditions. In-season disease management options, such as fungicides, can reduce economic impact. Scouting fields around V14, or just prior to tassel emergence, can help determine the level of disease pressure in a field.

Black Tar Spot

Black Tar Spot was first confirmed in Indiana in 2018 in the form of a yield-reducing epidemic. According to Purdue Extension, Fields in the most severely affected regions reached "100% disease incidence and over 50% severity on the ear leaf before the dent growth stage (R5/R6) with reports of 1345‐4035 kg/hectare (20‐60 bu/acre) yield loss."

Management of Black Tar Spot includes hybrid resistance and crop rotation, as well as some early season fungicides as a preventative measure. 

Understanding disease pressure is just one component in the decision to apply fungicide. Your Co-Alliance Agronomy team member knows the specifics of your field to maximize it's yield. Contact us to discuss your field-specific needs. 

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