Stalk rot of corn occurs when sufficient root tissues dies of starvation. This happens when its energy source, carbohydrates stored in the stalk, are depleted because of excessive draw to the grain versus the supply from leaves and stalk. Size of daily movement to grain is determined by genetics and environments. Soil moisture during time of silk extension is significant to more ovules being pollinated. Supply of carbohydrates during the season is determined by multiple factors: Hours and days of intense light, utilized by it C4 photosynthesis method to supply energy for more plant growth, storage of carbs in the stalk tissue as well as sugars to move to the grain after pollination. Individual plant environments such as competing with adjacent plants for light and mineral uptake can influence success in normal completion of transport of sugars to all pollinated ovules on each plant.
Seasons with extreme late planting dates in temperate zones have extra factors. Some fields will be fewer stresses in early season, resulting in less ovules pollinated, resulting in less grain but less stalk rot. Late planting dates still requires about 55 days after pollination to complete movement of sugars to the grain. It can be stopped with freezing the phloem within the stem tissue, with the result of light grain weight. Such a freeze may not result in stalk rot as remaining stalk tissue may remain intact.
If the below freezing temperatures were not sufficient to kill the stem phloem but did result in leaf death, depletion of the sugars in the stalk are intensified. This can increase death of stalk pith tissue, allowing stalk rotting fungi to digest the cells and weakening the stalk strength.
We should expect variable field results in Midwest USA in 2019.
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.