Identify Corn Diseases

Knowing Threat To Corn Yields Aids Treatment Selection

   Corn disease identification and fungicides were addressed recently by Dr. Heather Kelly, field crops plant pathologist with the University of Tennessee.


Dr. Heather Kelly, field crops plant pathologist with the University of Tennessee
recently explained that managing corn disease relies on the disease identification.
Photo by John LaRose, Jr.

   “Corn disease identification is very important in order to know how to manage it,” she began. She mentioned several different diseases, in particular, bacterial diseases which are not controlled by fungicides; she stated farmers must rely on hybrid resistance that’s built in as well as agricultural methods like rotation and tillage to manage bacterial diseases.
   “Fungal diseases are where fungicides can be beneficial in controlling diseases,” Kelly added. “Fungicides in corn provide very variable results and in research fungicide trials in corn we do not always see a positive gain in yields. Where we do see a more consistent positive gain in yield is when we are controlling disease and the best time to control disease with a fungicide application is at tassel or at silking stage VT to R1.”
   There are many fungicide products out there with variable rates that work very well, but farmers must first identify the disease they’re trying to control. Some diseases such as common rust rarely affect yield and hence do not call for a fungicide application; whereas southern rust can be very damaging to yield in the right conditions and may call for a fungicide application. In considering whether to spray fungicide on corn, four things need to be considered as to whether the effort will be beneficial.
   “The first is the hybrid, and how susceptible or resistant it is; second is your cultivation practices and the presence or absence of a disease,” she said. “If you’re in continuous corn, that increases your disease risk and that would mean that a fungicide is more likely to benefit you.”
   The third consideration is timing. Later planted corn may be more at risk of disease later in the season when the inoculum disease is built up in greater number and there’s a greater chance of  affecting yield. The fourth consideration is weather conditions.
   “You might have all three previous factors, a susceptible hybrid, continuous corn, and late planting and the disease may be present, but if the right weather conditions for the disease to develop do not occur then your yield might not be affected. The crop might not need a fungicide application,” Kelly summed.
   For more information on corn disease identification and fungicides in corn you can visit utcrops.com, and click on the left side for corn diseases. ∆
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower