|Northern corn leaf blight that has spread into the canopy beyond the ear leaf.|
There are many other stresses that can occur during ear development that can also cause plants to make less sugars such as lack of sunlight (cloudy days), drought, high plant populations (competition for light/reduced stalk), wind, hail, corn rootworm, corn borer (2nd generation), nematodes, corn planted after corn (higher disease), compromised roots from lack of oxygen (flooding) or root rot, nutrient deficiency (low N/ or high N with low K), high ear placement, or poor hybrid stalk strength.
|Corn that has shut down due to stalk rots.|
Unfortunately, corn could have undergone many of these stresses during the current growing season at corn kernel development. The developing ears take priority and the amount of sugars that they require will depend on kernel number. Root and stalk tissue have lower priority, and if under stress, they will receive less sugar and weaken. Hence, in their weakened state, root and stalk rot pathogens lurking in the soil/residue can infect and cause disease.
|Corn that is infected with anthracnose stalk rot.|
Check 10 plants by pinching the second or third internode of the stalk above ground level. Then, push the stalks and if they collapse easily, cut open the stalk to check for disease or insects. Stalk rot could be lurking in just one area of the field or affect an entire field. If more than 10% of stalks appear to have stalk rot, harvest these areas as soon as grain is physically mature with a slow combine speed.