Which fungus produces long, gray lesions on leaf surfaces?

The condition described, identified by long, gray lesions on leaf surfaces, is associated with the fungus known as corn gray leaf spot. This fungus is responsible for causing significant damage to corn crops by affecting the foliage, which ultimately impacts the plant's ability to photosynthesize efficiently.

Corn gray leaf spot is characterized by the appearance of long, rectangular lesions that are grayish-green to gray in color. These lesions typically start at the lower leaves and can progress upwards, leading to premature leaf senescence. This is crucial for farmers and agronomists to recognize, as controlling the spread of this fungal disease is important for maintaining crop health and maximizing yields.

The other options refer to different diseases or pathogens. Common blight, for instance, is a bacterial disease that causes water-soaked spots and lesions, while Fusarium root rot affects the roots, leading to stunted growth and plant death, but does not typically result in gray leaf lesions. Barley yellow dwarf virus is a viral disease that causes yellowing and stunting in plants, distinct from the gray lesions caused by the corn gray leaf spot fungus. Recognizing the specific characteristics of these diseases aids in appropriate management and control practices in field crops.