Which term refers to the physical evidence of the pathogen causing a plant disease, such as powdery mildew or rusts?

Which term refers to the physical evidence of the pathogen causing a plant disease, such as powdery mildew or rusts?

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

Answer: (D)

In plant disease terminology, signs are the physical evidence of the pathogen itself. When you see powdery mildew or rusts, you’re looking at the actual pathogen structures—spores, mycelium, or pustules—on or in the plant tissue. Those visible pathogen structures are signs, not just the plant’s response. Symptoms, on the other hand, are the plant’s reactions like yellowing, wilting, or spots that result from the infection. So the powdery coating or rust pustules are signs of the disease.

In plant disease terminology, signs are the physical evidence of the pathogen itself. When you see powdery mildew or rusts, you’re looking at the actual pathogen structures—spores, mycelium, or pustules—on or in the plant tissue. Those visible pathogen structures are signs, not just the plant’s response. Symptoms, on the other hand, are the plant’s reactions like yellowing, wilting, or spots that result from the infection. So the powdery coating or rust pustules are signs of the disease.