Which factor is not necessary for infectious plant disease development?

• A. Sunlight
• B. Susceptible host
• C. Plant Pathogen
• D. Favorable environment and time

Answer: (A)

Sunlight is not required for infectious plant disease to develop. What matters is the disease triangle: a susceptible host, a pathogen, and a favorable environment over enough time. If any one of these elements is missing, infection is unlikely. Sunlight can influence conditions like leaf wetness or temperature, which can affect disease progression, but it isn’t a necessary component. A pathogen can infect and cause disease in shaded or indoor settings as long as the host is susceptible, the pathogen is present, and the environment supports infection and growth over time.