Updated Corn Disease Calendar

Included in this blog post find the most updated corn disease calendar.  Since the last posting (April 20, 2013: https://www.mississippi-crops.com/2013/04/20/corn-disease-calendar/), some additional diseases as well as time of observation based on growth stage have been added.  Most foliar diseases occur at specific times of the year, therefore, scouting for corn diseases throughout the corn season is important.  However, in some cases, diseases such as southern corn rust can occur earlier in the corn growing season depending on the environment encountered.  For example, southern corn rust was observed in June during 2010 but not until late July during 2012.  Typically southern rust is a late entry into our corn production system as the disease blows into Mississippi annually from corn production areas to our south.  In addition, foliar diseases such as gray leaf spot can occur earlier than normal if excessive corn residue remains in the field over several successive seasons and continuous corn production has been common in the field.  But, with that in mind, GLS is not generally observed at early vegetative stages; however, GLS can occur as early as growth stages that immediately proceed VT/R1.  But, the fields where GLS has been observed on late vegetative corn have had between 7 and 10 years of continuous corn and GLS has been the predominant disease at that location.

The majority of the diseases presented in the attached calendar are foliar diseases.  Keep in mind that diseases such as charcoal rot, anthracnose as well as some of the virus diseases encountered in our production system are likely the result of infection that occurred at much earlier growth stages.  Sometimes, once the disease is observed it is difficult to judge when infection actually occurred depending on the specific disease.  Note that some diseases can show up in more than one growth stage (on the left column), but will ultimately depend on the environment encountered throughout the season and to a greater extent planting date.  But, in some cases, previous crop will also dictate the foliar disease pressure.  For example, corn following corn will likely have additional inoculum pressure for such diseases as gray leaf spot and northern corn leaf blight.  But, GLS and NCLB can also be observed in first year corn if the environment remains conducive for an extended period of time.  However, the inoculum to produce rust infection (common and southern) will have to blow into our production area from an overwintering source of inoculum generally from our south.

Updated corn disease scouting calendar (Corn Disease Calendar 2016).