As corn matures, and grain fill is completed, the usual challenge is to allow the grain to reach maximum loss of moisture before harvest without losing ability to be harvested due to lodging. This usually depends upon stalk strength after completion of grain fill. Hybrids do vary on the cellular structures of rind tissue, affecting the ability of the rind to be punctured with a penetrometer. Cellulose and lignin synthesis in the stalk tissue during plant growth is involved and affected by combination of genetics and minerals.
Although the rind resistance to breakage is significant, a solid stalk, with the pith tissue intact and attached to the rind, creates the strengthening dynamic of a rod versus that of a tube after the pith is pulled away from the rind when the plant wilts. This can be detected in a simple push test of plants after grain fill. Those with hollow stalks will easily pushover. These individual plants will also show symptoms of invasion of fungi such as species of Diplodia, Colletotrichum, Fusarium or Gibberella. These are the fungi most often identified on dead stalks, but several other species also attack the cell wall components of the rind. Presence of these fungi often lends credence of blaming the stalk vulnerability to the lodging on these fungi.
Intactness of the pith tissue, however, is probably the most significant factor in occurrence of late season lodging of corn stalks. This occurs when the plant wilts previous to completion of grain fill because insufficient carbohydrate is available to fill the grain and maintain life in the root. Wilting causes the withdrawal of the pith from the rind, thus significantly weakening the stalk strength. Fungi readily invade the dead tissue but the main strength weakening preceded their invasion.
Stalk lodging is affected by many factors. Genetics and pre-pollination environments affect ear height, root growth, photosynthesis, leaf disease, stalk rind and storage of carbohydrates in stalk pith tissue. Genetics and post-pollination environments affect the ability of individual plants to obtain completion of grain fill and stalk strength until harvest.
About Corn Journal
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.