Which term describes the physical characteristics of a plant disease expressed by the plant, with five categories?

• A. Sign (of a plant disease)
• B. Necrosis
• C. Lesion
• D. Symptom (of a plant disease)

Answer: (D)

In plant disease terms, what the plant shows as a result of the disease are called symptoms. They are the plant’s visible or functional changes—like yellowing of leaves, wilting, stunting, or necrotic spots—expressed by the plant itself in response to the infection. Signs, on the other hand, are evidence of the pathogen itself observed on the plant or its surroundings, such as fungal spores or bacterial ooze. So the correct term describes the plant’s outward reactions to the disease, not the pathogen’s structures. The other options point to either specific manifestations (like necrosis or lesions) or to evidence of the pathogen (signs), rather than the general plant-expressed category.