Trouble shooting late season corn problems

By Ryan McAllister, CCA
Team Sales Agronomist
Beck’s Hybrids

Agronomist Ryan McAllister pulled this ear on Friday the 13th, maybe that is the problem. More likely though, this is a result of corn after corn and a susceptible hybrid.
Root lodging
Through my travels as of late I have become concerned about the late season standability of corn hybrids in areas where soils have remained saturated for an extended period of time. It appears that in those areas, corn plants didn’t need to root down deep and therefore did not. I have already seen root lodging in areas in the central part of Ohio and East Central Indiana. The majority of this lodging was in fact “root lodging” and not stalk lodging. Upon digging roots, I am observing very small root systems in which the “money roots” (those roots that go deep for moisture) have been rotted off due to saturated soil conditions. I have received many calls from those concerned that this is rootworm feeding and their trait is not working. That is not the case. Saturated soils have caused root rot and a lack of deep root growth. The lack of roots and heavy rains have caused …

Nitrogen deficiency
Many customers have called me and stated that they sidedressed their corn so it cannot be N deficiency. It is. Some areas have received large enough rains to lose enough N to cause N firing. The vast majority of Indiana and Ohio have a combination of things going on. We not only have lost N but we have such a lack of roots that our corn plants are struggling to get all the N they need. What happens when our plants are suffering from N loss? Corn plants become more susceptible to leaf diseases, stalk diseases, cannibalization of the stalk to produce an ear, lower yield/test weight, and ear rots can all occur. What happens when our corn plants are suffering from root loss? Root lodging/stalk lodging can occur.

Ear rots
Southern Ohio is beginning to see ear rots again. Currently it is being seen in competitive hybrids that are susceptible, not to say that we can’t get it in ours.
According to the Pest and Crop Newsletter, August 6, 2010 Edition, “Ear rots can be exacerbated by high humidity. Recent observations of diplodia ear rot, even when corn ears are only half way through their grain filling period, are a direct consequence of excessive and prolonged humidity around the junction of the leaf sheath and ear shanks. Problems with ear rot will limit corn yields most on susceptible hybrids already under stress (such as those fields with deficient nitrogen).”

Anthracnose top dieback
I received a report from Brian Rice, DSM in north central Indiana that he has been observing quite a bit of Anthracnose top dieback. I noticed the same thing in southern Ohio yesterday. The top dieback form of anthracnose is a little less common than the infection that starts at the base of the plant and works it’s way up. Look for tops of plants that appear reddish purple or yellow and appear to dry or die out. If you remove those upper leaves you should be able to see black anthracnose lesions on the stalk itself. That is how you can tell the difference between top die back and corn borer. The infection happens earlier but late season stress appears to trigger the symptoms of the top dying back. This late season stress is usually very dry weather but could be being triggered by excessive heat/lack of roots/ etc. Nothing can be done to prevent any further spread of this, however, these plants could be more susceptible to stalk lodging. The degree of yield loss will be determined by the stage of the corn when symptoms were noticed.

The good news
1. Many fields look like yield potential is still very, very good in spite of the many challenges faced this year.
2. It is very important to be looking in your fields to see if you have any of the above mentioned challenges. Why? You can do something about it. If you have the knowledge of any of these problems in your fields, you can use that knowledge to make some adjustments. Maybe you need to shell that field of corn before you run beans this year. Maybe that isn’t what you normally do, but it may be necessary to prevent any further losses due to lodging.
3. Many early-planted corn fields are already at 25-50% milk line. We are not going to experience problems like last year with abnormally wet corn. That’s good news!
4. You have support! Remember, call your local dealer if you are concerned but just aren’t sure what to be looking for. We are your resource and are here to help!

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