Foliar Diseases Developing in Many PA Corn Fields

Posted: August 21, 2012

The return to wet humid conditions has primed many PA corn fields for an increase in disease pressure. Now is a critical time to walk your fields, assessing disease severity and not only planning for harvest but also looking towards next year.

Both corn and soybean maturity are rapidly advancing and now is the time to monitor maturity and evaluate individual fields so that you are not faced with any big surprises.  As you might expect, many areas of the state are 400 or even 500 heat units ahead of an average year.  This heat has sped the development of both corn and soybeans and may provide dairymen with some opportunities for fall forages such as making oat baleage.  Silage harvest is just beginning in earnest here in Lancaster County; while much of the early corn is showing white husks and at or approaching black layer.  Silage growers are faced with lush green stalks but rapidly maturing ears which makes harvesting at the proper stage of maturity a challenge.  Advancing maturity and a return to more frequent rains and high humidity has also brought on rapid disease development in many fields.  

Gray Leaf Spot (rectangular lesions), Northern Corn Leaf Blight (larger cigar shaped lesions) and other diseases such as Anthracnose (causes stalk rots and top dieback) and Carbonum can be found in many fields.  Now is a good time to get out in those fields and not only evaluate ear development but look at overall plant health.  Hybrids with significant disease should be signaled out and made note of.  Because disease often varies significantly from one side of the field to another, get a thorough look at your fields.  Other factors such as rotation, tillage type, and soil type will affect the spread of disease.  Remember that as the plant approaches black layer some disease development is often a normal occurrence during wet years, and generally does not significantly affect yield and standability.

Also, make note of problem hybrids and consider your management options for next year.  This may include: switching hybrids, crop rotation, residue management, and even fungicide use.  Foliar disease is often a sign that stalk and ear molds are prime for development.  If wet humid conditions are predicted to persist, consider chopping diseased fields or harvesting these as high moisture corn before additional problems develop.  The heat and acidification which occur during fermentation will often stop developing diseases resulting in good quality silage.  Inoculums or acids should also be considered to speed this conversion to stable fermented silage.

Many seed salesmen are already out in force and anxious to discuss their products and your needs for next year.  This is a great time to jump into your salesman’s truck and take a drive around your fields evaluating hybrids as you go. Many companies have numerous plot days in the coming month.  Why only pick a hybrid from a catalogue when you can attend a field day and get to kick the tires?!!

Contact Information

Jeffrey S Graybill
  • Extension Educator, Agronomy
Phone: 717-394-6851