Should I apply fungicide after a hail event?

Originally Published August 19, 2014

A fungicide application cannot recover yield potential lost due to hail damage. Fungicides protect yield potential by reducing disease.  Many studies have been conducted in the United States looking at fungicide application to hail damaged corn crops.  Most results show no yield response when a fungicide has been applied to hail damaged corn.  If after the hail event, conditions are conducive for fungal disease development, an application of fungicide may provide yield protection.  But again it won’t recover the yield lost due to the hail event.

Also keep in mind that bacterial diseases, such as Goss’s Wilt that infect plants through wounds, are not controlled by fungicide application.  And many diseases do not require a wound to infect the plant, including common smut and stalk rots.  Furthermore, foliar diseases that can be managed with foliar fungicides, such as gray leaf spot, do not need wounds for infection.

Bottom line is disease pressure plays a critical role in the magnitude and consistency of a yield response to a foliar fungicide application in corn.  So instead of basing a fungicide application on the fact that it hailed, it should instead take into account disease risk factors such as:

  • Susceptibility of the corn hybrid to various diseases that would be controlled by a fungicide application.
  • Previous crop as many foliar pathogens can survive on corn residue.
  • Weather since the risk for disease development will increase in rainy and/or humid weather.

If you do choose to apply a fungicide to hail damaged crops this year, it would be a good idea to conduct a replicated on-farm trial in the field to allow for a comparison of treatment effectiveness at the end of the growing season.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture


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