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Corn stalk quality can be compromised by the interaction between weather, fertility, compaction, leaf disease, plant population, planting date, and kernel filling. The result of these interactions can be stalk cannibalization as grain fill takes priority over all plant functions. Physiological lodging (stalk weakening caused by removal of nutrients from the stalk to supply developing kernels) can be just as severe as lodging caused by stalk rot diseases.
In response to stress, corn plants will mobilize sugars to fill the kernels thus resulting in reduced sugar content of stalks. This process is referred to as stalk cannibalization and causes disintegration of the pith cells. The weakened stalks are more susceptible to colonization by fungi and to physiological stalk lodging. While this is often called stalk rot, the fungi are primarily colonizing tissues that are predisposed due to any condition that reduces photosynthesis and the production of carbohydrates needed to fill grain and maintain stalk integrity. Physiological stalk lodging is favored by good growing conditions early in the season, followed by stress after pollination. Stresses can include a lack of moisture, nitrogen deficiency, foliar disease, hail damage, and prolonged cool, cloudy weather conditions. Extended periods of dry or wet weather prior to pollination, followed by abrupt changes for several weeks after silking, also can cause poor stalk integrity and occurrence of physiological stalk lodging.
The presence of stalk cannibalization and stalk rots in corn may not always result in stalk lodging, especially if the affected crop is harvested promptly. Many corn products have excellent rind strength, which contributes to standability even when the internal plant tissues begin to rot. However, this will not prevent lodging if harvest is delayed and the crop is subjected to weathering such as strong winds and heavy rain.
In-season options for managing stalk and ear rots are limited and fungicides are not labeled for their control, but proactive practices can help manage stalk and ear rots in future crops.
Sources: Nielson, R.L. 2003. Stalk health issues in stressed corn. Purdue University Department of Agronomy. https://www.agry.purdue.edu
Thomison, P. and Pierce, P. 2012. Drought may increase stalk lodging in corn. Ohio State University C.O.R.N Issue 2012-30. https://agcrops.osu.edu. 180208125853