Which symptom is commonly associated with plant disease rather than injury?

Discoloration is a symptom that is commonly associated with plant disease because it often indicates the presence of pathogens affecting the plant's physiological processes. In many cases, diseases caused by fungi, bacteria, or viruses can lead to yellowing, browning, or other color changes in the leaves or stems, which can be indicators of nutrient deficiencies, water stress, or direct pathogen activity.

In contrast, symptoms like localized wilting, mechanical damage, or leaf scorch are generally more indicative of physical injury or environmental stress rather than a disease process. Localized wilting often occurs due to insufficient water uptake, mechanical damage is caused by external forces (like pests or physical impacts), and leaf scorch results from environmental conditions such as high temperatures or drought, not necessarily due to a pathogenic infection. Thus, discoloration distinctly links to underlying disease processes, making it the most relevant choice in connection with plant disease symptoms.