Much of Indiana's corn crop has endured the slings and arrows of Mother Nature during the 1995 growing season. Delayed planting, restricted root development due to soil compaction, excessive heat, moisture deficits, and leaf diseases have all taken their toll on the photosynthetic factory that we call a corn field. It's important to remember that any time severe stresses occur in a developing corn crop, the risk of subsequent development stalk rot increases. The simplest explanation goes like this...
To satisfy grain fill demands, most modern corn hybrids utilize photosynthate (sugars and other carbohydrates) produced concurrently by the corn field 'factory'. Severe plant stress decreases the photosynthetic capability of the 'factory' during grain fill. In particular, cumulative effects of excessive heat, dry soils, and leaf diseases have caused premature death of leaves in the 1995 crop. Consequently, less photosynthate is available for kernel development and maintenance of stalks and roots. In addition to the direct effects on kernel development , the potential for stalk rots increases.
The worse the stress, the more likely that the damaged plants will remobilize stored carbohydrates in the stalks and leaves to meet the demands of the developing kernels on the ears. As carbohydrate levels decrease in the lower stalk tissues due to remobilization, susceptibility to the various stalk rot fungi increases. Thus, root and stalk rots can develop sooner than normal in stressed corn, causing an increased risk of stalk lodging prior to harvest of the field.
Growers should inspect potentially susceptible fields closely and regularly during the next few weeks to determine the occurrence and rate of development of stalk rots. Windshield surveys won't do the job! Choose your walking survey areas to adequately reflect soil types, soil drainage patterns, hybrids, rainfall differences, and soil fertility levels.
To estimate the severity of any stalk rot that develops, pinch stalks near the ground and also up toward the ears on a number of plants in each area of the field. A hollow shell of a stalk that collapses easily indicates advanced stages of stalk rot. If severe stalk rot develops in particular fields, plan to harvest those fields as soon as possible after the grain is mature (i.e., kernel black layer, about 30% grain moisture).
For more information on stalk lodging in corn, pick up a copy of AY-262, Stalk Lodging in Corn: Guidelines for Preventive Management, at your local Purdue University Cooperative Extension Service office.