Corn was stressed almost everywhere by to much heat. Where there was ample rain, the stress was less. Many fields, perhaps more than is yet known, if you believe anecdotal reports of crop scouts, have portions within the field whipped around by winds in an unusually high number of storms in parts of the country, particularly the northern and western parts of the Corn Belt, earlier this summer.
What all this boils down to is stress, and stress going into fall leads to stalk rots, ear rots in the worst-hit areas, and won stalks. All that can add up to the need for an earlier harvest to prevent harvest losses. It may or may not point to major problems with moldy corn. That one is yet to be determined. Chuck Woloshuk, a Purdue University entomologist and specialist on corn diseases, says the real test will be fall weather. Aflatoxin could be a problem in some areas, and then again it may not be a big problem, largely depending upon what happens from now through the rest of the season, he says.
One way to know if this is a likely problem in your fields or not is to do the pinch test or push test or both, notes Bob Nielsen, Purdue University Extension corn specialist. If stalks are disintegrating and fall apart if pinched hard, or if stalks drop over if pushed hard, stalk rots may already be a problem.
Various stalk rots are secondary invaders that prey on corn that has been stressed, with lower than usual defenses against diseases. They also are likely culprits to take up residence after insects have chewed into stalks or ears, leaving holes that makes it enter for disease organisms to find their way into the plants. That's one reason why western bean cutworm, a pest showing up more prevalently in certain parts of the Corn Belt these days, is so destructive. With four or five worm holes per ear, water and moisture enter the ear, and disease organisms quickly follow. The result can be a mess of sprouting corn complete with various molds, and insect damage to boot.
The best thing you can do now is be on guard for fields that appear as if they won't stand up long. You may want to reconsider your harvest plans or the point at which you wanted to start harvesting so you can get those fields before they deteriorate to the point that yield losses mount to unacceptable levels.