Corn in the Midwest USA is approaching the time of season in which scattered plants show whole plant death. It does cause confusion as to if it involves an aggressive pathogen or is it more of a physiological nature. Diagnosis is further complicated by presence of fungi such as Fusarium species or Colletotrichum graminicola, the cause of anthracnose.
If the symptoms include all leaves wilting and stalk color becoming yellow green then brown, the problem is caused by roots not being able to supply sufficient water to leaves to remain turgid. Resulting wilt results in all physiological activity in plant to stop. Abscission layers (black layer) develop at base of each kernel. It is tempting to call the disease by the fungi found in the dead tissue but the real problem is rotting roots.
Roots become susceptible to the many microbes in the soil as sugars from the leaf tissue after pollination is insufficient for the root cells to produce the metabolites needed to ward off the microbe invasions. As more root tissue is destroyed, uptake and transport of water declines. If the transport to leaves is insufficient to meet the loss of water via transpiration, the leaves wilt. The visibility of this wilting process occurs relatively sudden. Close observation may show a slight discoloration one day and complete wilt the next day.
The individual plant that wilts was probably determined by size of root during season, supply of carbohydrates after pollination and volume of carbohydrates moved to the grain. Each of these involve multiple factors. Plant density, plant uniformity, light intensities, number of kernels, leaf diseases are among them. Genetics and environments are obviously interacting. It is better to consider those variables than simply associate it with a disease.
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.