Protecting your Yield: Early Fungicide Application

A variety of university and industry research trials have shown that an early corn fungicide application around V5 can help optimize yields. Actual yield benefits can vary based on a number of factors including weather, rainfall, and yield potential of the corn hybrid, but models point to an increased chance of positive ROI from an early fungicide application regardless of planting date. If you planted on time, saturated soil conditions will likely mean higher early season disease pressure. If you planted late, applying a fungicide early could be the difference of developing a black layer or not.

The Disease Triangle

The disease triangle illustrates the three components needed for disease development: a susceptible host, a virulent pathogen and a favorable enviorment for disease development. Plant diseases can be prevented by eliminating any one of these components.

Of the two scenarios below, the scenario on the 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.

Plant Disease Triangle Scenario Croplan 3611SS vs Croplan 390922

The Outlook

The above map shows a prediction for the severity of Grey Leaf Spot on corn using the past 5 years of weather data. As you can see, the wet spring has set the stage for an appearance of the disease across the state with a 100% certainty of at least 20% disease impact.

Other Insights


  • Modern corn hybrids have incredible yield potential even when planted late IF they are managed for that potential. Modern hybrids produce big yield if they are kept alive to produce that yield. 
  • Wet soil conditions exacerbate crown rot and stalk rots. This year’s crop is likely to suffer from these diseases. Fungicides promote stalk strength and help a plant mitigate some of the consequences of these diseases.
  • Late planted corn is likely to be exposed to greater foliar disease pressure early. Our moisture patterns will favor the development of foliar diseases earlier than a typical year in terms of crop stage.  Therefore a standard tassel application may occur after significant foliar infection has already occurred compromising yield potential.


  • Soybeans are supposed to have a tap root system. This years planting into suboptimal conditions is likely to result in very poor root health (more fibrous than tap root). This leads to increase stress and risk of greater flower and pod abortion.
  • Beans are behind physiologically. They will flower earlier with fewer trifoliates than most years.  This means fewer leaves – fewer photosynthetic factories – meaning protection is critical. To preserve yield potential we need to protect leaves with fungicides and insecticides or risk leaf loss and less ability to feed flowers/pods, etc…
  • Diseases like frogeye are already present in soybeans.  Favorable conditions could leave to an explosion of frogeye similar to what we experienced last year where it certainly reduced yields.

How can I protect my yield?

Knowledge is power. If you know your hybrids, we can create the contact your Co-Alliance team member to look at the data and determine the best crop protection plan for your fields.

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