Which type of plant disease is caused by nematodes?

Root galls are indeed a type of plant disease caused specifically by nematodes, which are microscopic, worm-like organisms. When nematodes infect a plant's roots, they can lead to the formation of galls or abnormal growths, disrupting the plant's ability to absorb water and nutrients effectively. These galls create a stressful environment for the plant, often resulting in stunted growth, reduced yields, and, in severe cases, death of the plant.

In contrast, viral infections result from pathogens that invade a plant's cells and can cause a variety of symptoms, but these do not involve nematodes. Fungal infections are associated with spores and hyphae that spread and cause damage primarily on the aerial portions of plants. Leaf blight is generally caused by bacterial or fungal pathogens rather than nematodes. Each of these other options highlights different types of plant pathogens or conditions that are unrelated to nematodes, making root galls the correct identification as a disease specifically caused by these organisms.