Late season stalk rots usually involve several interactions between various fungi and the host plant biology. Most commonly fungi associated with corn stalk rot are Fusarium moniliforme, Gibberella zeae, Diplodia maydis and Colletotrichum graminicola but in fact multiple other fungi can be isolated from dead stalks as well. All of these species feed on dead plant tissue and create spores that are ubiquitous on and around corn plants all season. Part of the natural corn physiology is to defend against successful invasion of corn tissue even if the stem or leaf tissue is damaged by insects including corn borers. These defense systems are triggered when invaded by production of anti-fungal chemistry after detection, a common character of all living plant and animal organisms.
Living root tissue use this system to ward off the many microbes surrounding them in the soil. Root cells require energy to drive all of its physiology including the defense system. As an annual plant such as corn matures with energy in the form of carbohydrates drawn to the developing grain the roots need to compete with the grain for available stored and freshly produced carbohydrates. Corn root mass begins a slow deterioration a few weeks after pollination, perhaps because of the competition with the grain. Microbes quickly take advantage of the weakened defense system, digesting the dead tissue. If sufficient root tissue can function for the 55-60 days after pollination to absorb and transfer sufficient water to the leaf tissue to meet the loss of water through stomata from transpiration, the plant will maintain turgidity.
If the root rot causes the plant to not meet the transpiration demand, the plant will wilt. This becomes evident very quickly with a whole-plant symptom of gray leaves. Desiccation occurs in all plant cells, stopping movement of carbohydrates to all cells including those in the grain. This also stops ability to ward off the abundant fungi ready to digest the dying and dead cells in the stalk tissue. The more aggressive of these fungi are the ones that we associate with stalk rot.
Corn stalk rot has been studied by many researchers for a very long time. The dynamics of whole plant biology, biology of the fungi and environment interactions are complex. The photosynthetic stress-translocation balance concept of corn stalk rot was first proposed in 1975 to a group of corn pathologists in an attempt to unify previous research on aspects of the problem done by many researchers. That literature and further published information supporting this concept can be sent by postal mail with a request sent to firstname.lastname@example.org.
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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.