During the last 2 weeks, the appearance of many cornfields has begun to deteriorate, and many plants are now dead. Although we expect plants to be maturing about this time of year, clearly some plants are dying early. Statewide, we reached 50 percent silking by about July 19, which means theoretically, the average corn plant should reach physiological maturity by about September 14. We are well ahead of that pace for a number of reasons, but regardless of the reason, when corn plants don't live for the full season, they don't achieve maximum potential yields. Even though the kernels on prematurely dead plants display a black layer, the lack of kernel plumpness indicates they reached this stage too soon.
Every field is a little different, and there is almost always more than one factor involved.
Anthracnose top-dieback . This is a phase of the anthracnose disease that is less common than the typical stalk rot that occurs at the stalk base. With top-dieback, the plant dies from the top down, with the upper leaves turning yellow or reddish purple, then drying out. When these leaves are removed or fall off, typical black anthracnose lesions can often be seen on the outside of the upper stalk. If the stalk is split, the pith appears rotted in the upper internodes.