Should you apply corn fungicide now?

Simply finding northern corn leaf blight lesions or lesions caused by another disease is not a good enough reason to apply a fungicide to your corn fields, says Tom Allen, Mississippi Extension plant pathologist.

As he’s scouted Delta corn fields in recent weeks, Allen has identified two diseases — northern corn leaf blight and Holcus spot — “with regularity.”

Suggestions that farmers should be making blanket fungicide applications when NCLB is detected are wrong, Allen noted in the most recent issue of the Mississippi Crop Situation [1]. “Corn should be scouted and a fungicide applied in response to a yield-limiting disease situation.… A blanket fungicide application at tassel in the absence of foliar disease is not economical,” he said.

Agronomic considerations Allen says should be a part of a fungicide decision include:

• Row spacing

• Irrigation type

• Hybrid susceptibility

• Growth stage

• Number of lesions present and placement in the crop canopy

• Yield potential

• Number of years in continuous corn production

“In addition, depending upon disease pressure and weather conditions, a fungicide application will only provide 21 to 28 days of disease prevention — depending on the labeled rate,” Allen said. “In no way will a fungicide application provide protection until harvest if applied today.”

Bottom line: “The necessity to apply a fungicide should be made on a field-by-field basis.”

To read Allen’s discussion of Holcus leaf spot and northern corn leaf blight in Mississippi Delta corn, download a copy of the latest Mississippi Crop Situation [1].