Corn Disease Update

I was looking at some corn Monday and it is progressing well. Most is waste high or as tall as me, up to vegetative growth stage – V10. One thing we are watching for is disease. There is no known southern rust yet. However, Northern corn leaf blight and Northern corn leaf spot are two diseases being reported. Seminole Ag Agent, Rome Ethredge has seen both of these diseases and has some pictures. Here is a photo of Northern corn leaf blight:

NorthernCornLeafBlight-Rome

NCLB is more likely to be found in corn behind corn and with susceptible varieties. Its presence in the field does not automatically warrant a spray. Here are some thoughts from UGA Extension Pathologist, Dr. Bob Kemerait:

  1. All growers should scout for NCLB.
  2. All growers should recognize that conditions are generally favorable for NCLB.
  3. If after scouting, no lesions, or only a very few are found, delay applying fungicides.
  4. If more lesions are found or a susceptible hybrid is planted, grower should way options for protecting crop BEFORE tassel.

Another disease that showed up last year was Northern corn leaf spot. The spots look similar but has this barky, tree bark appearance. Here is a photo by Seminole Ag Agent, Rome Ethredge:

NorthornCornLeafSpot-Rome

Northern corn leaf spot is DIFFERENT than Northern corn leaf blight. Here are some comments from Dr. Kemerait:

I do not have any data on the use of (or need for) fungicides in the management of northern corn leaf spot.  In discussions with Dr. Dewey Lee, we are both uncomfortable with reports of this disease this early.  Although I do not have recommendations for use of fungicides on this disease, growers need to be aware that it is active in the state.  Also, I believe that growers should assess the development of this disease and may consider us of fungicides IF development and spread seems to occur in the field. Again, at this time, we do not have recommendations for Northern corn leaf spot.

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