The Disease Triangle and Fungicide Chart for Jacobsen Hybrids

The Disease Triangle and Fungicide Chart for Jacobsen Hybrids

There are so many different things that must be managed for a successful crop. One of those is choosing whether or not to use fungicide to control foliar disease in corn. Diseases such as gray leaf spot, northern corn leaf blight, southern rust, and others are of concerns because leaf infection is essentially damaging the solar panels that producing grain. Minimizing damage to the leaf helps to maximize the energy put into the grain and therefore yield is maximized.

For foliar diseases to progress there must be three things that come together: A pathogen to be present, a environment conducive to fungal growth, and a susceptible host. We visualize this idea with something called the Disease Triangle. When all three sides are present the triangle is complete and disease is present. Examples of conditions that allow for a complete triangle include

Pathogen = Abundant primary inoculum

  • Infected residue still on the soil surface
  • Strong southern winds and/or storm systems bringing inoculum in on the wind such as Southern Rust


  • Warm but not hot temperatures
  • Plenty of rainfall (inoculum can be splashed on to lower leaves)
  • Extended periods of leaf wetness such as heavy dews


Work with you Jacobsen Seed Representative to understand is fungicide application is right for your farm.