Corn Stalk lodging
Breakage of stalks in the 2nd or 3rd internode above the soil is a big concern during harvest. Multiple studies have been done attempting to sort out the dynamics of physical strength of the stalk and fungi associated with lodged stalks. Multiple fungi capable of digesting the cellulose and lignin of corn cells surround the corn plants in the field. Most of these are warded off by the anti-microbe metabolites of living corn cells. Fungi that successfully attack dying or dead cells, producing recognizable fungal structures such as Diplodia (Stenocarpella) maydis, Gibberella zeae, Colletotrichum graminicola and Fusarium sp. as well as several others that are found in the deteriorated stalk.
Methods of Evaluating Stalk Quality in Corn, published in 1970, (https://www.apsnet.org/publications/phytopathology/backissues/Documents/1970Articles/Phyto60n02_295.PDF ) is a summary of the dynamics crushing strength of lower stalk pith and rind versus intensity of Diplodia maydis. Both pith integrity and rind thickness are significant contributors to the crushing strength. Their study and others point out that the Diplodia fungus grows only in dead pith tissue, and, therefore, correlation of this fungus with weakened stalks is mostly related to death of pith tissue.
When individual plants wilt, usually because of root rot, the pith cells dehydrate, pull away from the rind and lose production of the metabolites needed to restrict growth of the fungi of the stalk. This results in weakening the strength of the stalk by changing the dynamics of pith attaching to the rind plus allowing the growth of fungi that can break down the rind cells.
It is interesting to observe (from the roadside) multiple fields in our area with very little stalk lodging. Plants are obviously dead from maturity and low temperatures. In general, lower stalks that make it to black layer without wilting, maintain strength for a long time. Dynamics involving environment, genetics of response to environment and vulnerability to root rot are significant in corn stalk lodging.
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The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.