Which of the following is not a primary living disease agent?

Which of the following is not a primary living disease agent?

• A. Fungi
• B. Virus
• C. Nutrient toxicity
• D. Bacteria

Answer: (C)

Primary living disease agents are organisms that can invade plant tissue and reproduce to cause disease symptoms. Fungi and bacteria are classic examples of living pathogens that colonize tissues and disrupt normal function. Viruses, while not cellular, are still considered disease-causing agents because they rely on living host cells to replicate and spread. Nutrient toxicity, however, is an abiotic condition arising from chemical imbalances or excess nutrients in the environment; it does not involve a living organism infecting the plant, nor can it reproduce or spread like a pathogen. So nutrient toxicity is not a living disease agent, even though it can produce disease-like symptoms in plants.

Primary living disease agents are organisms that can invade plant tissue and reproduce to cause disease symptoms. Fungi and bacteria are classic examples of living pathogens that colonize tissues and disrupt normal function. Viruses, while not cellular, are still considered disease-causing agents because they rely on living host cells to replicate and spread. Nutrient toxicity, however, is an abiotic condition arising from chemical imbalances or excess nutrients in the environment; it does not involve a living organism infecting the plant, nor can it reproduce or spread like a pathogen. So nutrient toxicity is not a living disease agent, even though it can produce disease-like symptoms in plants.