Which disease produces pustules on grass blades, releasing spores that can be rubbed off by hand?

The disease that produces pustules on grass blades, which can be easily rubbed off by hand, is leaf rust. This disease is caused by a type of fungus that infects the leaves of grass, especially in conditions of high humidity and temperature. The pustules filled with spores are characteristic symptoms of leaf rust, giving the leaves a distinctive appearance. These spores can be dislodged from the pustules by hand or through mechanical means, leading to the spread of the disease to other plants. The presence of such pustules is a key indicator for diagnosing leaf rust, and understanding this symptom helps in identifying and managing the disease effectively.

Other options, while associated with various grass diseases, do not exhibit the same pustule formation or the ability to rub off spores by hand. Thus, recognizing leaf rust is important for proper disease management in turfgrass and maintaining lawn health.