What is a visible effect of stalk rot on corn stalks in August?

The visible effect of stalk rot on corn stalks in August is characterized by a loss of firmness. Stalk rot leads to the degradation of the inner stalk tissue, causing the stalk to weaken and become increasingly soft and mushy. This deterioration impacts the structural integrity of the plant, making it prone to lodging or breaking, which can severely affect yield potential.

The other choices do not accurately reflect the effects of stalk rot. Excessive green color might indicate healthy growth or over-fertilization, while an increase in height and enhanced leaf growth would suggest optimal conditions for the plant. In the case of stalk rot, plants display signs of decline, such as loss of firmness, rather than growth or vigor.