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Don’t Misjudge Corn Fungicide Timing

June 5, 2018
this agronomic image shows southern rust

Southern rust

The growing season is underway which means corn foliar diseases could soon begin to emerge. If a fungicide is part of your disease management plan, it’s important to understand proper application timing in fields where foliar diseases are present, in order to protect your corn yields this season.

We recently ran a Twitter poll asking @SyngentaUS followers to identify the optimal time for a single fungicide application in corn to achieve best protection from diseases and highest yield potential. The results of the poll revealed:

  • 12% chose V4-V8.
  • 74% chose VT/R1.
  • 12% chose brown silk.

While you may get a good return from an application at V4-V8, university research shows corn growers get the greatest return from applications made at VT/R1 and the least at brown silk.

The University of Wisconsin Extension lists several risk factors that make corn susceptible to foliar diseases, which can affect when a fungicide is applied:

  • Previous crop: Many foliar pathogens survive in corn residue, so the risk of infection from foliar diseases increases when corn is planted in a field for a second season in a row.
  • Weather: Wet, humid conditions are favorable for foliar disease development. As long as conditions are dry and hot, diseases are more likely to be suppressed.
  • Field history: If a field has a history of foliar diseases, the risk of foliar corn diseases appearing the following year increases.
  • Field location: Fields located in low areas or surrounded by trees have a higher susceptibility to foliar disease development.

The University of Wisconsin Extension says you should begin scouting just before tassel emergence, but it’s best to start scouting as soon as possible. Consider applying a fungicide if disease symptoms are present on the third leaf below the ear or higher on at least 50% of the plants.

The goal of a fungicide application should be to protect the ear leaf and leaves above the ear during the grain fill period, since these leaves contribute more than 75% of the plant’s carbohydrates. Even if only a few lesions appear on the lower leaves before or at silking, a fungicide application is necessary.

Just as important as getting the right timing is choosing the right fungicide. Trivapro® is the only fungicide on the market that can be applied at R1 and last until harvest. Applying Trivapro at VT/R1 timing will provide the hardest-working and longest lasting control of rust, gray leaf spot and Northern corn leaf blight. In addition, its plant-health benefits will help maximize the grain fill and protect stalk integrity for improved harvest efficiency and reduced volunteer corn the following year.

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