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Stresses such as nutrient deficiencies, diseases, insect feeding, excessively wet or dry conditions, high winds, and hail can lead to stalk lodging.
Figure 1. (A) Anthracnose stalk rot: shiny, black discoloration that can not be scratched off the rind; (B) Charcoal rot: tiny, black sclerotia produced inside the stalk give the appearance of charcoal dust; (C) Diplodia stalk rot: tiny, raised black dots (pycnidia) on lower nodes are embedded in the stalk and can not be scraped off; (D) Fusarium stalk rot: pinkish-white fungal growth on outside of stalk, pink or salmon colored discoloration inside stalk, lack of visible reproductive structures, crowns often are brown and rotted; (E) Gibberella stalk rot: bright pink to red discoloration at the nodes; (F) Bacterial stalk rot: dark brown water-soaked lesions at base of stem with soft, slimy stalk tissues accompanied by an extremely foul odor.
In general, stalk rots are favored by late season stresses. A number of fungi and bacteria cause stalk rots in corn which can lead to stalk lodging. In addition, stresses such as nitrogen deficiency and blighted leaves from foliar diseases can inhibit the production of carbohydrates, causing plants to remobilize or move sugars from the stalk and leaves to fill the kernels. This process is referred to as stalk cannibalization and can make corn plants more susceptible to physiological stalk lodging.
Push or Pinch Test. Scout fields periodically after pollination to check for stalk rot and lodging issues. Walk a zigzag pattern through the field and test stalk firmness by squeezing or pinching each stalk at one of the lowest nodes above the brace roots. Healthy stalks are firm and cannot be compressed. If a stalk feels soft, it is likely prone to lodging. Check at least 100 plants per field.
A second method for determining potential stalk lodging is to push each stalk about 5 to 8 inches from upright (approximately a 45° angle) and note whether the plant springs back, remains tilted, or breaks.
If more than 10% of the stalks in a field are rotted or prone to lodging, consider scheduling the field for early harvest. In severe instances, it may be more economical to harvest early and dry the grain post-harvest as opposed to accepting significant field losses.
Insect feeding creates entry wounds for pathogens to colonize plant tissues. In some cases, planting products with insect resistance such as SmartStax® RIB Complete®, VT Double PRO® RIB Complete®, or Genuity® VT Triple PRO® RIB Complete® corn blends can reduce the incidence of stalk rots.
1Jackson-Ziems, T.A., Rees, J. M., and Harveson, R.M. 2009. Common stalk rot diseases of corn. EC1898. University of Nebraska-Lincoln Extension. http://extensionpublications.unl.edu/. 2 White, D.G. 1999. Fungal stalk rots. Compendium of Corn Diseases, third edition. APS Press. Web sources verified 08/10/16. 150720155008.