Labeled Fungicides for Corn Disease Management

Over the past several years the type, as it relates to the specific active ingredients, and number of fungicides have drastically changed for corn disease management.  In the attached table, information has been provided that was collated by the Corn Disease Working Group (CDWG).  The CDWG is composed of extension and research plant pathologists from throughout the U.S. corn belt who meet annually to discuss corn pathology issues.  In addition, one of the outcomes of the meeting is the information contained in this table CDWG 2013 fungicide efficacy table.

Information contained within the table presents how fungicides compared to one another in head- to-head comparisons with several common diseases that occur in MS.  Note that some of the information contained within the table regarding the most recently labeled fungicides (e.g., Evito, Aproach, Domark) has not been completely filled out.  Since some of the fungicides included in the table are new to the corn market they have not been tested long enough in efficacy trials and plant pathologists feel additional information is necessary before the table columns are filled out completely.  I am planning on evaluating several of the products listed in the table in some efficacy trials at a location with extreme gray leaf spot pressure this season.

I’d also like to add one important comment.  Even though common rust is listed in the provided table I am not an advocate of suggesting that a fungicide be applied for common rust management.  Rarely has common rust been a yield reducer in MS or other states for that matter.  Common rust is a typical disease that occurs following a flush of nitrogen in the corn plant.  Rarely will the disease cover much leaf surface area.  Remember, a corn plant is large, and has a tremendous amount of leaf surface area.  Generally speaking, I have not seen common rust cover more than 1/10^th of 1% of the entire leaf surface.  Keep this in mind prior to making a fungicide application.

Also, please be aware that the harvest restriction is important when making a fungicide application.  The harvest restriction has been set by regulatory agencies and typically pertains to the presence of a particular active ingredient.  Note that fungicides that contain only a strobilurin ingredient can typically be applied to corn up to and included 7 days prior to harvest.  However, when a fungicide contains a triazole or carboximide the harvest restriction is generally longer.

As with any fungicide application, read and follow label instructions as to the need for an adjuvant.

Keep in mind, additional information regarding corn diseases and the time of year when they generally occur can be found in:

https://www.mississippi-crops.com/2013/04/20/corn-disease-calendar/

Also, information regarding the response of corn to vegetative fungicide applications can be found:

https://www.mississippi-crops.com/2013/04/28/are-early-vegetative-fungicide-applications-beneficial-for-enhanced-corn-production-part-i/

https://www.mississippi-crops.com/2013/04/28/are-early-vegetative-fungicide-applications-beneficial-for-enhanced-corn-production-part-ii-impact-of-fungicide-on-greensnap/